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6-screw Bases, How NOT To Do It

As you can clearly see from the pix below, this new custom Encore barrel put out by one of the big name shops clearly demonstrates that you cannot use the normal 6-screw spacing on tapered barrels.


Here you can see a stainless plug screw backed out to the same plane as the straight shank of the barrel over the lug.

It should be as obvious as a train wreck that the screw located on the taper of the barrel will bend the scope base downward.

However, this new barrel came from this premier, big-name after market barrel maker exactly as you see it.

Viewed from the top

Having more than 4 screws has its merit, and I do convert and install bases with more than 4 screws, but there is a right way to do it.

First, for 6 screws with the spacing shown, it must be done on a barrel with a longer straight shank or a straight barrel with NO taper.

When I do install a base with more than 4 screws, I normally only add 1 screw ahead of the standard 4.

The spacing between the short spaced pairs is .836″, the common pattern used originated with untapered Contender barrels and is simply another pair “leap frogged” forward of the original 4.

Note that the 5th hole from the rear is right on the breaking point where the barrel begins its taper so that it, too, may tend to bend the base some.

When I install a 5th screw I locate it at around .7″ to .750″ forward of the original 4 screws, staying back behind where the taper starts.

The above is an example of why you cannot use these 6-screw bases with 6 screws on tapered barrels such as tapered Contender 10″ barrels and any of the production TC Encore centerfire barrels

Here is how I anchor the tip of the base so it cannot spring up & down.Click on this link to see how I run one screw down to TOUCH the taper of the barrel, then add the 6th screw INTO the barrel so the overhanging part of the base cannot spring up and down with each shot, cause vertical stringing of shots, and add stress to the scope tube.

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Secure Scope Base Mounting

If finger tip pressure on a scope base overhanging the taper on a barrel moves the base up and down, stop and think what happens to your scope and rear scope ring during recoil.

Take the flexing out of the base for more secure scope mounting and less strain on your scope and scope rings.

Adding a screw contacting the barrel at the extreme forward tip plus a screw INTO the tapered part of the barrel stabilizes the tip of the base and stops vertical flexing of the scope base during recoil.

Barrels with muzzle brakes that depress the muzzle during recoil compound the strain on the base, scope, and rear ring especially.

Here is an example of vertical stringing of shots due to the unsupported portion of the scope base flexing as reported by Blaine D.

“When attempting to sight in my 338-06 barrel (at 100 yards), it was obvious that every shot was hitting approximately 1″ higher than the last one. After about 6 shots, I had to spin the turrets on my scope to bring the bullet impact back on the paper. 5 more shot fully confirmed that the bullet impact kept hitting about an inch higher each time. Bullet impact also gradually strayed to the right about 2″ during all of this. At this point, I noticed that the gap between the barrel and the bell objective was smaller than when I first mounted the scope. When you mentioned tension on the scope tube, everything clicked together and made sense. At first, I couldn’t figure out how the base could move, but yet still remain tight and solid. Based on your remark, I reasoned that the when the base is flexing during recoil, the scope tube is probably shifting in the rings, but does not shift back after the recoil. This creates tension between the scope and the base, resulting in the base being held in a stressed state. This also results in the scope pointing downwards more with each shot. This would explain the upward vertical stringing. I took pictures of my scope, particularly the gap between the bell objective of the scope and the barrel. I measured the gap between the barrel and the scope itself (not the rubber cap) using feeler gauges. It measured 0.119″. Then I removed the top half of one the rings to relieve any tension. I felt and heard a distinct pop as the rings shifted position on the scope as soon as I loosened the rings. I remeasured the gap, and it measured 0.150″. The gap widened 31 thousandths of an inch! No wonder the bullets keep continually walking up the target with each shot. The tension in the scope tube was pressing and holding the tip of the base down more and more with each shot.”

The steel Burris base is potentially more rigid than most aluminum bases, but in spite of this, note the gap between the front bell of the scope and the barrel in this top picture, then note how the gap has closed after shooting.

See the inset close ups in the upper right corners of the photos.


Now, note how much smaller the gap is below the bell in the photo below.


Flexing the scope downward stresses the scope tube and the rings. The scope cannot return to its at-rest position. Poor design choice, and for no logical reason.


Here is how I solve the problem by stabilizing the front tip of Weaver-type and EGW picatinny rail scope bases that overhang the tapered part of the barrel.

Note the small headless set screw through the far left end of the base. This screw just contacts the surface of the barrel.

The next screw from the left is threaded INTO the barrel.

NOTE: Locations of the two front screws varies from photo according to the application.

Pictured is the Weaver #410 base modified so the front tip is anchored. We give the picatinny rails the same treatment to eliminate the “diving board” effect.

 

Anchoring the front tip stops both the flexing downward as the barrel moves up in recoil, and if there is downward force on the barrel from a muzzle brake, the screw INTO the barrel opposes it.

The front tip of the scope base overhanging the tapered part of the barrel is held rigidly in place.

In the style of mounting pictured here, one more screw is added at the point just behind where the taper of the barrel begins….. what we refer to as “6-screw” attachment, 5 screws in the straight shank of the barrel, plus 1 into the tapered part of the barrel.

Screws used are Weaver-style “oval head” screws, not flat bottomed “fillister head” screws that can shift.
I have become pretty hard nosed over the years when it comes to using flat bottomed head screws simply because the base can move a few thousandths in any direction due to the clearance around the screw shank and nothing to keep the head itself centered.

At a minimum, if I do use a flat bottomed head screw I put a tapered seat in the base to center it. But I prefer to use the Weaver style screw, “V” head in a “V” seat so the base must stay centered and cannot shift.

This may be a minor detail that may or may not show up on paper, but fundamentally the security of a “V” assures the base cannot move in any direction.

Muzzle brakes that have the ports angled back DO in fact put a fore and aft strain on screws and scope rings, creating more potential for the base to move front to rear, rear to front with each shot.

It’s all about doing things as right as theoretically possible.

Do this simple test with Weaver style bases installed with just the standard 4 screws!


Place one finger against the front end of the base at the gap where it overhangs the taper of the barrel.

Now, with or without a scope on the base put finger tip downward pressure on the front tip of the base with the other hand.

When you release that pressure, you will feel the base flexing upward
…… as obvious as a train wreck!

This is just finger tip pressure. Stop and think about the sudden force of recoil upward.

If the base is flexing, the scope has to be flexing with it, and you have all that leverage being applied to the rear ring….. and the scope tube, too, of course.

Add to your barrel purchase from us either EGW picatinny rail or Weaver base installed with front tip of base stabilized $59, billed separately, base included. Picatinny base installed with front tip of base stabilized $79, base included.

Note that hole patterns added are not “standardized”. I vary the hole pattern according to the application.

Picatinny bases are 3/4″ longer & provide more eye relief. (Click Here)

More eye relief and more places to position scope rings as well as locations for adding more scope rings to keep the scope from slipping in recoil.

6-screw Weaver scope bases on UNtapered barrels still $49
This applies ONLY to the UNtapered, straight, Contender S-14 type barrels, current production “G2″ barrels, and UNtapered Encore custom barrels where the untapered shank of the barrel is AT LEAST 3 1/2” long so as to provide support of the base at all 6 screw locations.

Mike Bellm email: mike@bellmtcs.com
Phone: 541 956-6938


SCOPE BASE INSTALLATION 101:

Just put the screws in the holes and screw the base on, right?

WRONG!

It is often a big mistake to just grab the base and screws and start twisting screws.

Here are some basic steps for intelligently installing scope bases and not jeopardizing a hunt with a scope base rattling around and while minimizing the risks of base screws stripping out.

1) First clear the barrel screw holes of any debris or thread locker, ie, “Loctite”, that will interfere with turning the screws all the way in.

I grind all but about 1 thread of leade off the ends of taps and chase each hole with a tap. IF you are up to it and comprehend what to do, I take ALL the leade off of at least one tap and grind the very bottom end like an end mill so that it will actually cut flat at the bottom of the hole.

I find that many factory screw holes are too close tolerance to start a dead flat-ended tap into and must use a starting tap first before going to the dead-bottom tap.

Kurt supplies taps and tap handles on our website.

No taps? Acetone helps.

2) Common 6×48 scope base screws MUST have no less than 4 threads of contact. 5 or more is required for optimum strength where EXISTING hole depth permits. (I don’t recommend drilling holes deeper than original.) Many scope base screws as supplied by the manufacturer have a minimal or insufficient thread contact.

Put the base on the barrel, run each screw in tight…. one at a time…., check for wiggle of scope base, then UNscrew it, counting the number of turns before it is free from the hole.

3) If a screw is too long, obviously, it cannot pull the base down tight to the barrel and screws may need to be shortened.

Repeating, install the base but only tighten one screw at a time, making sure that the base is pulled down tight by each screw….. NO wiggle.

After tightening all screws, remove them and examine the bottom end of each screw for a bright spot in the finish indicating the bottom thread and/or the end of the screw is being “munched” on the very bottom or the leading thread at the bottom of the screw threads.

If they are being “munched”, shorten the screw by at least the amount of the bright surface damage you see, then go through the process again to be sure you have taken off enough. Screws showing a “munch” on the end will tighten down further with the “munch” removed.

4) If you do not have at least 4 threads of contact (5 or more is optimum for 48 pitch screws) get longer screws or deepen the contersinks in the scope base. Brownell’s sells piloted countersinks for this purpose, but in a pinch a common drill bit can be used….. best done in a controlled manner on a drill press or mill for those of you who have that capability.

(Grind the unthreaded “nib” off the end of screws….. common to Weaver’s screws. That nib wastes at least one potential thread.)

Short Summary:
1) Make sure screws are not bottoming out in the holes and preventing the screws from pulling the base down tight.

2) Make sure you have at LEAST 4 thread of contact, ie., 4 turns of the screw.

How tight?
I believe the rule is supposedly 20 inch/lbs. of torque.
HOWEVER, I put ’em on to stay, no doubt exceed 20 inch/lbs., and am prone to breaking screw driver tips. Allen, Torx, and slotted screws will limit you to how much torque you can apply.

Bases on barrels sent in indicate many of you hardly use enough torque. Go for TIGHT. If the barrel threads are in decent condition and you have enough thread depth, it is highly unlikely you will strip threads….. but use a little good sense about it.

CAUTION!
Regarding open sights on TC factory barrels……..
While open sights installed by TC are often only finger tight and must be checked for tightness. HOWEVER…. the open sight screw heads are quite thin and prone to breaking! Tighten them, yes, but don’t get carried away!

Avoiding stripped screw head slots:
1) Use only a hollow ground screw driver in good condition that fits the slot. Meaning, do not use a wedge shaped common screw driver.

2) Bear down hard on the TOP end of the screw driver to minimize the tendency for the screw driver blade to force itself out of the slot. Use one hand to bear down, and the other to turn the handle.

Some general rules for Contenders and Encores:

1) Most Contender scope base holes are about .135″ deep, except for .45/70 barrels which are only .125″ deep. On most scope bases, screws will be pretty much level with the bottom outside edges of the base. More recent production barrels sometimes have holes .150″ deep. On average, standard .135″ deep holes will give you about 4 to 4 1/2 turns, ie, 4 to 4 1/2 threads, of contact.

2) Standard hole depth for Encores is approximately .185″ with the potential for at least 7 threads of contact. Encore base screws will project 2 or 3 threads below the bottom level of most scope bases.

3 threads or less and a bit of recoil is almost guaranteed stripped out threads!
You would think that barrel and scope base manufacturers would assure adequate thread depth, right?

WRONG!
Don’t count on it!

I had a an Encore barrel in the vise recently with only THREE, that’s right 3 threads in the holes…… totally derelict and inviting “the unwashed”, trusting shooter to either a disaster with the scope flying off, or if it made it to a hunt, the potential of ruining a hunt.

Thread lockers:

I put scopes on to stay and use only “permanent” red Loctite, but “your mileage may vary”.

Is thread locker necessary?
Not necessarily, especially if you are prone to changing scope mounts from time to time.

Stuck screws, tips on how to remove them:

1) Simply smacking each screw with a flat punch and hammer will sometimes “break the seat” enough to free them.

2) Breaking the seat makes a tiny void for penetrating oil like PB Blaster to wick in and soften the thread locker. Smack each screw, apply penetrating oil, wait a few minutes, then try each screw. If a screw moves at all, give it more penetrating oil, wait awhile, and try again. You may have to repeat this a number of times. It works for me most every time.

3) Kurt is a proponent of using a soldering iron to heat each screw. 400 degrees softens thread lockers like Loctite. Makes sense, but I have yet to try it myself.

4) If the steps above won’t free screws, you may have to resort to drilling off the head of the screw (s).

Use a drill bit #27 or larger, centered with the screw head, and drill only a little at a time until a black ring starts to appear in the hole you drill…… indicating you have gotten to the screw shank….. then STOP once the head is free. Don’t get carried away and just keep drilling. Sneak up on it!

You want to leave as much of the screw itself as you can so that once the head is cut from the screw shank and the base is lifted off you have enough screw sticking out of the barrel to get ahold of with pliers to turn the screw shank out of the hole. Side cut pliers make their own flats to grip the screw and will let you get down closer to the barrel for a sure bite on the screw.

Stripped hole threads:

Best option is to chase the threads with Brownell’s “over size 6×48” tap, aka .146″x48, then use their “Oversize 6×48” screws. The tap and screws are a bit spendy, but worth having if you have to remove many scope bases.

Broken taps and sheared off screws:
Most often either will result in damaged hole threads if drilling them out is attempted. Much of the time it is necessary to go a step larger with screw size, either .146″x48 or 8×40.

While not looking for such work, I do scope base and screw hole work routinely.
Costs vary and may require going up to the next larger screw size, #8×40.

Mike Bellm

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Precision Recrowning

Much of the time factory and even a lot of “custom” crowns are cut off center and/or out of square with the bore. There are other ways to go about it, but this is the best I have come up with in the last 34 years.

All too frequently, bores are not centered at the muzzle.
Factory and much “custom work” produces a surface at the end of the bore that is out of square to the bore. With the barrel turning between centers, the end of the barrel wobbles like a bent car rim.

This means that one point of that surface is farther ahead than the other. Gas then escapes behind the bullet from the side that is shorter, kicking the bullet into an exaggerated yaw that results in eratic impact points on the target, ie, poor accuracy.

The bullet needs a uniform push from all around its base at once to get a straight departure from the muzzle.

Just simply holding a barrel by its exterior and making a cut does not give a cut square to the bore IF the bore is not perfectly centered with the outside of the barrel. This is ESPECIALLY true when a barrel is shortened.

No bore is perfectly straight, and when you get back away from the end of the barrel, the bore can be very radically off center…. ie, not in the middle of the barrel. There has to be a correction made for this condition in order to get a square, centered cut, regardless of what shape of crown one uses.

Some like radiused crowns like found on a lot of factory rifles, particularly of older vintage. Some like perfectly flat crowns while some like a more angled crown, and the benchrest crowd theorized the escaping gases leave at an 11 degree angle, no matter what, so 11 degree has become vogue as the precision “benchrest crown”.

No matter how it is shaped, it must be centered and square to the bore itself.

Piloted tools in general….. piloted crowning tools specifically: No matter how you slice it, no matter how warm and fuzzy a pilot may make you feel, the fact is that a pilot simply CANNOT in reality keep things precisely lined up. There are situtaions where a piloted crowning tool has some merit, but no matter how you go about it, it is not perfect. It will always have the potential to allow misalignment to varying degrees.

A crown cut with a piloted tool, done right, is better than the proverbial “jab in the eye with a sharp stick,” but still not as good as a crown can and should be done.

My method references off the bore itself, dialed in to within .0005″ of true center of bore.

Barrels shorter than 20″ are done with the Bondo and pipe sleeve method shown below. No matter how far off center the bore is, the crown is cut centered with the bore to within .0005″ and square to the bore. Plus, it protects the barrel’s finish.
Yes, there are other ways to go about this, and on 20″ and longer barrels I do have a smaller lathe where I can put the barrel through the spindle, then dial in the bore.

One could turn a true section on the end of the barrel and run it in a steady rest. Not pretty.

With a short enough spindle, large enough spindle bore in the lathe, and a long enough barrel, yes, one can certainly put the muzzle in a 4-jaw chuck and dial it in. However, this will usually produce some rather ugly marring of the finish

Too much work!
That is what some folks doing barrel work seem to think about my method.

And, it is a significant amount of work, yes.

Mmmmm….. which is to say they don’t think you are worth it.
My thought is, if it isn’t worth doing right, it isn’t worth doing, and

you deserve better!

Here’s the process I use when recrowning all barrels under 20″ and when doing the internal work in my muzzle brakes on all lengths of barrels, starting with a good dose of release agent on the barrel.


Nothing too sophisticated. Most of the time I use some old lithium cup grease. Lately I have been first slathering on some good old fashioned Turtle Wax car wax, letting it dry well, then apply a thin film of grease.

Swiss cheesed piece of pvc pipe slipped on

Flutes in the barrel or ports in the barrel for my muzzle brake provide a “Key” to keep the sleeve from rotating on the barrel.

Plain old Bondo auto body filler is then goobered well into the holes in the pipe filling the voids inside. Before the Bondo “kicks”, the previously inserted cleaning rod and patch that kept the Bondo out of the good part of the bore pushes the Bondo and patch out the muzzle.


Use the cheap stuff. “Premium” fillers can adhere too well and are harder than necessary for the job, plus can be more difficult to remove as a result of both.

3/4 in. pvc pipe fits most barrels up through .810″ diameter Contender and heavy production TC factory Encore barrels, including the “Pro Hunter” rifle barrels.

Tapered barrels require some tape wrapped around the barrel or toothpick size wood shims, etc. to shim the pipe kinda centered with the barrel.

Barrels require drilling and tapping for a sight screw to anchor the pipe sleeve when recrowning.

Barrels ported for my muzzle brake use the ports to anchor the Bondo and sleeve.


That’s a screw with Bondo goobered to it sticking up at the rear of the pipe.

When the Bondo is well hardened, the barrel is then run between centers turning the pipe sleeve and body filler down to the inside diameter of the bearing that will be put snugly on it.

.984 in. is perfect for the 25mm bearing I use for most jobs.
Heavier barrels require a larger bearing. For the larger diameter barrels I use a bearing with a 1.180″ inside diameter.

The bearing is then put on, hopefully with a little effort, but not enough to break the Bondo loose.

Shop rag across the ways helps keep the mess under control. Any type will do. It does not have to be floral pattern like this one. ūüôā

A little light weight oil does wonders, and if the bearing goes on a bit too easily, grease snugs things ever so slightly while giving the sleeve a little bit of “float” that tool pressure tends to equalize.

Note that “live centers” have a certain amount of runout in them, so I use nothing but a carbide “dead center” in the tailstock, except for the largest bore sizes, .45 and over, for which I do not have a carbide center large enough.

The steady rest is then installed, and a dial test indicator is used to make sure the steady rest posts are adjusted to true center of the bore.


As the steady rest posts are brought into contact, the outer bearing race is pushed back toward the headstock, firmly holding the chamber end against the center in the chuck.

From the side it looks like this.

For inquiring minds, the lathe is a 1980 South Bend 14×40 I bought new and have worked on exclusively these last approx. 30 years.

Note that I do not use a dead center in the spindle…. for a couple reasons.
1) I use an adjustable back chuck that is very closely dialed in, and I do not want to disturb it, even though, yes, I can dial it in again….. but why?
2) I lathe turn a bar of steel in the chuck so that the center is then as precise as the bearings in the headstock. I do this every time I install a center to turn something between centers.

It is a choice of the lesser of the evils. This is the evil I like best.

Note the fancy brazing job on the bolt extending the lathe dog to reach the chuck jaws. Why so long? Works best for Contenders, which is what it was originally made for over 20 years ago. Not the prettiest, but an old friend.

With compound set for 11 degrees off of square, cut is made such that as much tool pressure as possible is directed outward, away from the bore, to minimize tool pressure inward that tends to roll a burr to the inside.

I use mostly tool steel with some rake, lots of clearance, very sharp, and dress it with a Diamond EZE Lap before each final cut.

Those who are familiar with machine work understand the terms. For the laymen, get some books on machining.

Note that if the original crown or a saw cut is not perfectly square to the bore, the cone shaped center cannot “see” the true center of the bore. Most barrels require squaring the original crown or saw cut first, then turning the sleeve a second time, farther back to get the sleeve’s surface concentric with the bore.

And, by the way, a big percentage of barrels leave here shorter than they were when they arrived. This is another example of “Have it YOUR way”!

An accumulation of end cuts at the saw. Note most of the shorter pieces are buried under the longer pieces tossed in on top.

Much of the break open single shots’ handling qualities are lost to overly long barrels on one hand, and on another, there are many, many applications where a shorter barrel simply makes more sense for use in close cover or where compactness is really needed on an atv or as a quick handling “truck gun”.

Then of course there is the option to cut down a rifle barrel to get the weight and length you want in a handgun barrel. I also drill and tap rifle barrels for the handgun forend screw hole spacing.

Quite a few muzzle loader barrels also get abbreviated, both with plain, beveled crowns for easier bullet seating or with the “QLA” or “Bore Guide Muzzle” precision cut.

Any indication of runout in the bore is a result of either the center not “seeing” true center of a badly out of square end of the barrel or the steady rest pushed the bore off center.


You can see runout pretty easily, especially with the tool next to the spinning edge of the bore. Or, use a dial indicator or coaxial indicator to measure the runout.

In any event, runout means you start all over, turning another section of the pipe with the barrel between centers to get the bore running true, on center in the bearing.

Checking runout with a dial test indicator


As noted above, an out of square muzzle or the steady rest posts pushing the bore off axis results in a crown that is less than concentric with the bore.

The dial test indicator lets you tweak the steady rest posts to get the bore on axis. If it cannot be brought back on axis, then the muzzle end is squared, and the process repeated.

I shoot for a .001″ or less T.I.R., that’s “total indicator reading” to the layman, meaning the bore is on axis to within 1/2 thousandth, .0005″ on axis in any direction.

For barrels over 19″, I can also do crowns dialed in as above but with the longer barrels stuffed through the headstock on a smaller lathe.
This requires a bushing/sleeve over the barrel closer to the chamber end to center it in the spindle of the lathe and protection of the barrel’s finish at the muzzle end. Stainless steel shims are used to get the bore adjusted so it is running true with the same minimum runout as described using the Bondo-ed pvc pipe sleeve above.

This is what the end product should look like, no pun intended. You can see the outline of each land and groove…. NO BURRS smudged over.

Note I break the outside corner of the barrel instead of leaving a sharp corner like factory barrels that tend to put excessive wear at the muzzle end of gun cases.

There are mixed feelings about the extreme edge of the bore and ends of rifling. Some like to give this area a light polish with fine emery paper, though I prefer a clean enough cut that no polishing is necessary.

However, I have been known to do both and feel there is nothing compromised by breaking the sharp edge with emery paper pressed against the end of the bore while the barrel is turning. It could also be argued that a uniform and slightly radiused edge is better and less susceptible to damage as from cleaning rods, jags, etc.

As a final test, I like to drag the shank of a cotton swab over the edge of the cut. If it feels sharp and drags on the shank, I polish a little until the shank of the cotton swab glides smoothly across the edge.

This is the same setup I use for lathe boring the expansion chambers inside my muzzle brakes, as well as doing the crown inside at the ends of the rifling.
The difference is I am using indexable carbide boring bars to do the internal work.

It is messy work, somewhat tedious work, but the only practical way I know to get the job done accurately while protecting any finish.
All the epoxy dust and crud gets into everything and requires some healthy, thorough “sanitizing” afterward. That is the reason I batch the work rather than going through the whole process turning the dead center in the chuck, setting up the compound for the cut, and doing all the extensive cleanup for just a job or two.

Why do it? You deserve it done as right as I can do it.
Is it mandatory for every barrel? No.
Interestingly, some pretty crappy factory crowns still shoot well, so if this applies, it ain’t broke, so don’t fix it.

I also have a method to clean up light burrs on crowns without all the above work and do it no charge. However, the touch up can only do that, touch up. It cannot correct for lack of symmetry and squareness that can only be done between centers, referenced directly off the bore and with no runout.

If the crown looks reasonably good, shoot it first and see what it does, but some are so pitifully, sloppily done there simply is no choice but to redo them.

Why make this information available?
It underscores the difference between what you get in most crowns and what a crown should be. If a crown is not perfectly symmetrical about the bore, and you cannot see the outline of the riflings….. well, something is just not right.

If it doesn’t look right, it probably isn’t. And if it does look right, there is a much higher probability that it IS at least reasonably right. However, I have been surprised a number of times when a crown looks pretty darned good, but when put between centers the crown cut wobbled all over the place, totally out of square to the bore it is supposed to be referenced off of.

I’ve spent 30 years scrutinizing every vintage of TC crown, bitterly disappointed day in and day out. Were it not so, I would not have gone to the extent I have to correct them.

I also firmly believe we need more high quality local support for all shooters, particualarly fellow TC shooters. I certainly cannot do it all, and in these somewhat tough times and times ahead, it will likely become more and more important to have local access to guys with a lathe that give a damn about you, their fellow shooter.

And….. I’m no longer 32 years old and feel it’s time to pass more along to others.

The Bottom Line:

If you are going to do it, do it right.
While piloted crowning tools are better than nothing, there is no way they can keep the crown cut truly square to the bore like you can when the bore is dialed in.

All the best,

Mike Bellm

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Pillar Bedding Forends for best accuracy

Pillar Bedding Forends for best accuracy.

As barrels heat up during firing, they move causing small but very significant changes in their points of contact in the forend barrel channel.

These changes in contact effect the barrel’s vibration patterns and thus where the bullet will impact the target from one shot to the next.

It is often absolutely necessary to minimize the effects of these changes to get even acceptable accuracy.

Pillar bedding has proven to be the most reliable bedding method when a forend will be used on barrels other than the one to which it was bedded.

Pillar bedding, like most all tasks associated with the Thompson Center Contender, G2, Encore, Pro Hunter, and Endeavor firearms is quite simple once the concepts and basic steps are laid out.

The concept is very basic.

Metal pillars are epoxied into the forend in such a manner they project up into the barrel channel so that the forend’s ONLY contact with the firearm is at the metal pillars.

ALL contact between the forend and the barrel and frame is completely eliminated.

The finished product looks like this:

The barrel channel is widened and deepened to give ample clearance for the barrel, including the area marked in red at the rear of this TC factory walnut forend.

Step 1

Open the barrel channel IN FRONT OF the tapered part at the rear. Initially, I suggest leaving the tapered part original to help in centering the forend.

This is best done with a professional barrel channel rasp sold by Brownells, for example.

I do not recommend sand paper, since it usually results in rounding and wallowing the top edge of the wood making a rather crude, unsightly end product. Keep the top edge clean and sharp.

I suggest at least .020″ clearance at all points down the channel. One way to arrive at this is to wrap about 7 to 10 layers of masking tap to the barrel. When the channel is large enough to accept the barrel wrapped in tape, clearance is established.

Step 2


Make and install metal pillars, sleeves around the forend screws.

End adjacent to the barrel should be either radiused or V cut.

Pillars should let the screws reach almost to the bottom of the barrel screw holes.

The pillars shown are made from 5/8″ aluminum bar stock turned down to about .6″ to fit freely in a 5/8″ counterbored hole.

Screw heads can be counterbored into the pillar or left flush on top.

Grooves are cut into the pillars for epoxy to key into.

7 to 10 layers of tape wrapped around barrel at two points center the barrel in the channel and create “standoff” between the barrel and forend.

The same number of layers of tape on the frame centers the forend “ears” with the frame. Forend ears must not touch the frame and must be opened up also. A fine cut rasp works well.

Step 3

Counterbore the forend for the pillars.

Counterbores must be deep enough for the forend to fit the barrel and frame without the pillars bottoming out in the counterbored holes.

I chose 5/8″ material for my pillars for a more rigid contact with the barrel, though smaller pillars as small as 5/16″ have been used very successfully.

Material does not have to be aluminum. Steel tubing would likely work well also.

Forend ready to bed

Step 4

Epoxy forend to pillars.

Prep the areas for epoxying, first putting 1 layer of tape under pillars and 1 layer of tape inside barrel channel at each pillar, cutting out the tape over the counterbore holes neatly with a sharp knife. This makes cleanup a lot easier.

Put 1 layer of tape over the screw head ENDS of the pillars to KEEP EPOXY OUT OF SCREW SLOTS ON OFF OF THE SCREW HEAD ENDS OF THE PILLARS. FAILURE TO DO SO MAY MAKE IT MUCH MORE DIFFICULT TO CLEAR EPOXY FROM THE HOLES IN THE FOREND AND ACCESS THE SCREW HEADS.

Put release agent on exposed barrel surfaces to keep stray epoxy from bonding forend to the barrel.

Put one layer of tape around forend screw holes on the outside of the forend to keep epoxy off the finish. Neatly cut tape away from the small hole openings so excess epoxy can be squeezed to the outside.

Tape the front of the frame to maintain clearance and keep epoxy out of frame. Don’t forget, we need clearance at ALL points, including the front of the frame.

Apply epoxy to both the pillars and to the insides of the counterbores.

Step 5

Squeeze the forend onto the barrel until it is pulled down all the way. The 7-10 layers of tape wrapped around the barrel are the stopping point.

Once the forend is pulled down all the way onto the forend, wrap tape around the forend and barrel to hold it while the epoxy “kicks”.

IMPORTANT!

Watch the epoxy closely for first indications it is starting to kick There is a brief period where the epoxy loses its adhesive, sticky qualities and is easily cut like soft clay.

As soon as it is no longer liquid, JUST starting to firm up, cut/pick/scrape ALL the epoxy from the small holes from the outside.

Scratch the tape off the screw heads so you can access the screws with screw driver or allen wrench as the case may be. Remember, once the epoxy is cured, you have to be able to remove the screws.

Step 6 AFTER the epoxy has cured.

Clean up.

Remove tape holding forend to barrel.

Remove screws from forend. If you did not remove the epoxy while it was soft, you will have a problem getting to the screws to remove them.

Remove forend from barrel. Pillars STAY IN THE FOREND.

Remove all tape from barrel, frame, and forend. You should only have a small trace of epoxy to skive away from around the pillars.

Step 7. End Result

Pillars epoxied INTO the forend permanently project up into the forend channel about .020″ or more, and there is NO forend contact at ANY point on the barrel or the frame, including both the sides and front of the frame.

Relieve the tapered part of the barrel channel where the barrel makes its first step down in front of the barrel lug. This is the area marked in red X’s.

The barrel is now as fully floated as it can be with the forend attached to it, and the small contact points around the screws affect the least amount of influence to the barrel as it heats, moves, and vibrates while shooting.

Notes:

Some details are not pictured, but the above shows the basic concepts and steps to the process to get the end result of a floated barrel.

At this point we do not sell pillars or the counterbores.
Counterbores are available from most all machine shop and wood working supply houses such as Grizzley.

David White, for one, will make pillars for you as well as do the complete bedding job. His phone is (918) 244-6284.

I personally do not do any wood work for others. The above factory forend is one I did for my own use and for demonstrating the concepts behind the system.

The above information is copyrighted by Dennis M. “Mike” Bellm for individual use only and may not be copied or distributed, either for free or sold.

Pillar Bedded Forends, stocks & grips custom made by Dr. Tony Gettel.
Click on the link above for fine wood work with forends already pillar bedded

Posted on

Sims Barrel De-Resonator tests

In quest of good information and not a condemnation of the device, here is a report of one man’s tests of the Sims Barrel De-Resonator.
Foreword by Mike Bellm.

What we are after is a fix for problem barrels that exhibit poor accuracy. If barrel harmonics can be eliminated in the process of finding the true cause of inaccuracy, then a better guided course of action can be taken in choosing what remedial action is necessary.

In other words, if there are other problems in the system, such as loose hinge pin fit, too much or too little headspace, or forend bedding problems, all the rechambering in the world is not going to fix these problems.

You can have a $500 custom barrel with a perfect chamber and throat and still not get good accuracy if there are other deficiencies.

Charlie’s results below are from barrels that shoot well to start with…. the only ones he keeps….. and in this situation, just the reverse of what is expected occurred. He experienced degraded accuracy instead of improved.

We are waiting for reports from the other two testers, one of which has indicated improvements so far.

From .300 H&H; Mag rifle barrel

Before and after groups.

Larger group circled lower left is with the De-Resonator installed. Sub-inch 3-shot group to the right is without the De-Resonator.

This was a barrel I rechambered for Charlie, a factory blued barrel.

Sims Barrel De-Resonator installed

Charlie’s Report

Afternoon Mike,
Just returned from wringing out the Sims allegedly small group inducer. Four hour and almost a 100 assorted rounds. Bottom line I think it is
a gimmick. If you will look at some of my targets the 300 H & H that you
rechambered actually opened up when the rubber doohickey was on the barrel.
It by the way is very capable of shooting one hole groups sandbagged at 100 yards if I do my part. The first three shots in a heated barrel and
going for record included two bullets in one slighter larger hole. Adding
the rubber… not only made my rifle look ugly it opened up the group. I
stuck to three shot groups because I figure guys want this for hunting and
three shots is all they will ever get. So I tried it on a 30 inch fluted VV
338 Galaxy barrel. It did not tighten groups but moved them two inches to
the left of point of impact…so it does do something with harmonics. I
tried it on the end of the barrel and next to the forend…with little
difference in accuracy. Putting on a 30-30 with a folding stock opened my
groups. On a 300 Win Mag with a folding stock no difference. If you have
another volunteer I would be very happy to send this thing to them…it is
not something I want to pack around in the woods.
Hope this helps.
Regards Dr Charlie


And Another Similar Report


Sorry for the delay but deer hunting come first. I’m very disillusioned with the performance of my only TC rifle barrel with or without the deresonator. I therefor selected the most accurate barrel in my arsenal and proceded with testing. Tested was a Browning single shot with 26″ octagon barrel in 6MM Rem Cal. The resuls are attached. Identical conditions were used in both sets of shots with cool down between shots. Results are attached and speak for them selves.

Posted on

Headspace, How to get it right.

This Page Can Save You Thousands of Dollars!

Correct headspace is essential to accuracy, reliable functioning, and good case life. Here is how you measure it, make corrections, and also measure throat length.

The first thing you must do is understand that headspace is not a length, which flies in the face of the industry concepts geared to gauging chamber depth. The term has been badly adulterated in common usage to the extent the term is not something the average guy can relate to.

But thinking of the term headspace for what it REALLY means, it becomes a very simple concept that is both easy to understand and easy to measure, especially in any break open gun like the TC Encore or Contender/G2. I’ll show you how.

Too many barrels are given up on as unsatisfactory, or, worse, folks leave the TC system in despair simply because of headspace issues. Don’t be one of them! The methods you get away with shooting bolt actions simply do not work with springy break open actions. The break open actions are different and must be handled differently.

Understanding headspace can literally save you hundreds of dollars, thousands of dollars if you are one who does a lot of barrel swapping in your quest for accuracy and the performance dreams are made of.

This is what it ideally should be, .001″ “SPACE” BETWEEN THE CASE “HEAD” AND THE BREECHFACE, “head” “space”.

.001″ to .003″ is a good range to work in since it is often difficult to keep ammo consistent to within .001″. But the more space there is, the greater will be the problems associated with it.

Conversely, if there is NO space between the case head and the breech face, meaning the case sticks out of the chamber too far, this is also a major problem related to accuracy and even preventing the barrel from closing all the way. If the barrel is not closed all the way, you cannot cock the hammer on the Encore or G2, nor will the Contender hammer block safety be released so the gun can fire.

Here is just one example:

Drawing courtesy of Alan Thompson. Thanks, Alan.
Note that the case shoulder is in contact with the chamber shoulder while there is space between the case rim and the bottom of the rim counterbore, indicating the case is “headspaced” or its forward movement stopped by the shoulder, not the rim, and that the actual protrusion of the case head is .001″ less than whatever the barrel-to-frame gap actually measures.

Here is the short course:
In the example above you would
1) measure the barrel-to-frame gap with a common feeler gauge set (IF the barrel is not actually hitting on the firing pin bushing,

2) measure where the case head is in comparison to the end of the barrel, (ie. dead flush with the end of the barrel, however many thousandths below the end of the barrel, or in the example above how many thousandths it sticks out of the barrel), then

3) do the simple arithmetic.

Let’s put some hypothetical numbers to the diagram above. Let’s say the gap is .005.” To arrive at the optimum .001″ space between the case head and firing pin bushing, the case would have to stick out of the barrel .004″.

In summary:
Gap minus protrusion equals.001″.

IF the case were, let’s say, .004″ BELOW the end of the barrel, the “space” between the case “head” and firing pin bushing it would go like this:

Gap, .005″, PLUS .004″ equals a total of .009″.

This is WAY too much of course, so you make corrections detailed below.

Our simple system of taking measurements lets you track and work out what works best for you, to include controlling the amount of interference on the case head to compensate for a less than tight barrel lockup if necessary, but you monitor and regulate it based on measurements for consistent results, not “guess and by golly.”

Note in the example above that headspace is regulated by size die adjustment so there is both contact on the case shoulder and .001″ clearance behind the case head…. ie, “head” “space.”

Another approach is to bump the case shoulder back so it does not touch the chamber shoulder, and the case rim does bottom out in the rim counterbore in the end of the barrel. In this situation, you would shim the firing pin bushing forward as necessary and remove material from the end of the barrel as needed to make that possible.

Whichever forward stopping point you choose to use, chamber shoulder or rim counterbore, you take measurements so you know what the resulting headspace is that your method is producing.

 

You cannot count on magazines, reloading manuals, the TC factory, the local “authority” who has “reloaded for 40 years,” or even most of the dealers and TC aftermarket custom shops.

Diagrams in loading manuals don’t seem to really help get the concept across.

Most gun writers themselves don’t seem to comprehend it.

If the factory understands anything other than SAAMI steel headspace gauges, it does not show, nor are they helping you understand and work with it.

The “local authority” who has double slammed the barrel shut for nearly 40 years certainly is no help, nor is the guy who has worked mostly with fixed barrel bolt actions going to be any help.

And some of the worst offenders putting out erroneous information are some of the custom barrel makers. These are usually the ones leaning on headspace gauges for everything.

In fact, when it comes to the TC and NEF Handi-Rifle type break open guns, the best thing to do with steel headspace gauges is toss ’em in the trash.

They are meaningless, and misleading at best. A “gauge” means nothing to you at all when you can take the measurements yourself and KNOW exactly what the headspace is WITH THE ACTUAL AMMUNITION IN THE CHAMBER.

It is the space between the actual cartridge case head and the breechface you are concerned about, not a steel gauge that may be substantially different from the actual ammo you are shooting.

So don’t go waste money on steel gauges. You don’t need them, and you don’t want them. After you have worked with our Headspace Indicator you will understand why.

Here is a perfect example of why you cannot rely on steel gauges….click on this link and see why you must measure the headspace produced by the ammo you are firing.

 

STOP RIGHT HERE!
CLICK ON THE LINK ABOVE. ONLY ABOUT 1/4 OF YOU READING THIS PAGE BOTHER CLICK ON THE IMPORTANT PAGE LINKED TO ABOVE!
(Gotcha! The site statistics page does not lie. Now go back and see it.)It is a clear cut example why you need to be conscious of headspace shooting factory ammo as much as or even more so than those who reload!

Whether you shoot factory ammo or reload makes no difference. You still must KNOW what the headspace is in any given barrel and frame combination.

You will be able to identify excess headspace with either factory ammo or your reloads. If the headspace is excess with factory ammo, anything over .006,” you have grounds to exact a remedy from the manufacturer of the barrel or the ammo manufacturer or both.

Excess headspace is the cause of many misfire situations and eratic ignition which produces poor accuracy.

No headspace, meaning the case head is hitting on the breechface when you close the barrel, can cause the barrel to not close all the way. This has been a major cause of misfires with Contenders since the first day they were produced. Or, with Encores and G2s, it prevents the hammer from cocking when the barrel is not closed all the way.

The issue of headspace is simply about making sure ammo fits the gun.

This should not be a strange concept. However, believe it or not, ammo that fits right is more likely to work right. Imagine that.

 


OK. Are you ready? Here goes!
Put your thinking cap on and hold on for the ride.

What IS headspace?

It IS what the word says.
It is “space” between the cartridge case “head” and the breechface, ie., “head” “space.”

The term is tossed around loosely all the time and presumed to be something you have to use a “headspace GAUGE” to measure, which is not only far from the situation, but also grossly misleading.

WATCH OUR YOU TUBE VIDEOS ABOUT HEADSPACE & BARREL TO FRAME GAP. Click on this link to see a quick demonstration of how to measure the barrel-to-frame gap properly and how to calculate headspace.

Repeating, “HEAD,” as in cartridge case HEAD, “SPACE,” as in the space behind the head,

or the distance from the case head to the breechface.

In the TC guns, it is the distance from the case head to the firing pin bushing in the breechface which actually protrudes out from the frame a few thousandths.

This is what headspace is, and it is very easily observed and very easily measured.

Headspace is NOT a length, either!
You read it all the time, everywhere, such as “…. the headspace of the .300 Win. Mag. is .220”.

Talk about screwed up bs! That .220″ figure is the LENGTH of the cartridge from the case head to the top of the cartridge belt dimension. It is used to gauge the depth of the chamber. BUT .220″ is NOT the “space” between the cartridge case “head” and the breech face….ie, NOT “head” “space.”

OR, take the .30/06. The steel gauge used to gauge the depth of the chamber is 1.940″ from the head of the case to the midpoint on the shoulder. Everywhere you go, you read or hear, “The headspace of the .30/06 is 1.940”.
NO…. THE 1.940″ DEPTH OF THE CHAMBER IS NOT HEADSPACE. IT IS THE STANDARD MINIMUM DEPTH OF THE CHAMBER. PERIOD!

Those depths of chambers tell YOU nothing at all about where the case head is in relationship to the breech face in YOUR given barrel, ammo, and frame combination.

Are we clear on this matter?

Do you get the point?

HEADSPACE IS NOT A LENGTH INTO THE CHAMBER!

What Headspace Is NOT…. It is not the barrel-to-frame gap. Click Here

Headspace is NOT the distance from the end of the barrel to the breechface, as is so often said erroneously.

The distance from the end of the barrel to the breechface has NO bearing whatsoever on headspace, and this gap, referred to as the barrel-to-frame gap, also has absolutely NO bearing on the quality or function of the barrel. And contrary to statements by at least one purveyor of custom barrels, there is NO optimum gap for accuracy. It can be a little, or it can be a lot, as much as 1/8″ and still have absolutely no bearing on accuracy.

While to some it may be more esthetically pleasing to not be able to see daylight between the closed barrel and breechface, the amount of the gap has no bearing whatsoever on the quality of the barrel, the function of the barrel, or the headspace.

In fact, there SHOULD be some gap between the end of the barrel and the firing pin bushing. If the barrel hits on the firing pin bushing, it can do two things:

1) It can prevent the barrel from dropping into the frame far enough to allow the barrel to close all the way and thus prevent it from firing, and

2) we are finding that if it is not hard contact it can often cause severe vertical stringing of shots that ruins accuracy. In other words the end of the barrel is just bumping randomly on the firing pin bushing during the firing cycle.

Both the barrel not closing all the way and vertical stringing related to the barrel hitting on the firing pin bushing should be corrected by facing material off the end of the barrel via filing, lathe turning, or milling. There should be at least a few thousandths clearance between the end of the barrel and the firing pin bushing. Do not worry about taking off too much material. The barrel-to-frame gap can be up to 1/8″, approximately the depth of the extractor slot. While this is extreme, and it is not necessary to remove this much material, the point is that the amount of gap has no bearing whatever on headspace unless it is a rimmed case, and you take off more than about .050.”

A gap of .003 to .005″ is ok both esthetically and functionally, but taking off more than this does not hurt anything either.

To set up a barrel and frame combination so that there is no gap or minimal gap can be a gross mistake, one discovered when the barrel is later installed on a frame whose hinge pin holes are somewhat closer to the breechface than the frame the barrel was set up on.

HINGE PIN HOLE LOCATIONS DO VARY FROM FRAME TO FRAME. I have only found about a .003″ variance from frame to frame while some report as much as .008″ variance. But once again, a barrel that hits on the firing pin bushing on one frame may not close on the next frame if the hole in that frame positions the barrel closer to the firing pin bushing.

Background behind the Bellm Headspace Indicator

The Bellm Headspace Indicator was developed as a result of my many years of measuring case head protrusion from the ends of barrels to determine the proper depth to ream chambers and is THE EASY WAY for the average reloader and real pro alike to quickly and accurately determine EXACTLY what the headspace is with his resized cases, rimfire ammo, and with factory ammo as well, of course!

For years I used a depth micrometer in the shop for measuring how far a case or headspace gauge protrudes from the chamber, but after all these years a depth micrometer is still rather touchy to get an accurate measurement with while balancing it over the end of a case head and being very careful to sense when the quill of the micrometer actually contacts the end of the barrel. Getting lazy, or smarter in my old age, I started using a dial indicator set up on the cross feed of the lathe to measure how far the case heads stuck out. But few people have a lathe handy for doing this.

For about a year I toyed with the idea of making this task simple and accurate for the amateur and real guru alike. I think I have “bingoed,” and once you try it, I think you will wonder how on earth you ever managed with the old ill-infomred methods we all used for years.

Keep this TIP in mind as you read on:

You will also find that there is a “sweet spot” where the case head is neither too far from the breech face of the frame or jammed forward by the breech face when the barrel is snapped shut. This “sweet spot” is where mysterious Contender misfires disappear, failure to cock with Encores and G2s disappears, case life improves, and where the gun shoots its best. It will also prevent many extraction problems that result from cases improperly sized being crammed into the chamber and then not readily extract.

The bottom line is that chambers and throats have to be cut to a certain depth. But it is YOUR responsibility to make sure your ammo fits the chamber.

Understanding what to do and being able to take the measurements tells you exactly what you have so you can get it right.

The Bellm Headspace Indicator lets you take the same measurements I have to take.

You expect me and anyone else cutting a chamber to cut it to a certain depth, and for good reason. Things have to fit right to work right.

So how much sense does it make for you to either cram a round in that is too long in the body and sticks out of the barrel too far OR falls too far down into the chamber?

Either is bad. Both cause problems. I am expected to do my part, now I am enabling you to intelligently do your part.

This is what it ideally should be, .001″ “SPACE” BETWEEN THE CASE “HEAD” AND THE BREECHFACE, “head” “space”.

.001″ to .003″ is a good range to work in since it is often difficult to keep ammo consistent to within .001″. But the more space there is, the greater will be the problems associated with it.

Conversely, if there is NO space between the case head and the breech face, meaning the case sticks out of the chamber too far, this is also a major problem related to accuracy and even preventing the barrel from closing all the way. If the barrel is not closed all the way, you cannot cock the hammer on the Encore or G2, nor will the Contender hammer block safety be released so the gun can fire.

Here is just one example:

Drawing courtesy of Alan Thompson. Thanks, Alan.
Note that the case shoulder is in contact with the chamber shoulder while there is space between the case rim and the bottom of the rim counterbore, indicating the case is “headspaced” or its forward movement stopped by the shoulder, not the rim, and that the actual protrusion of the case head is .001″ less than whatever the barrel-to-frame gap actually measures.

Here is the short course:
In the example above you would
1) measure the barrel-to-frame gap with a common feeler gauge set (IF the barrel is not actually hitting on the firing pin bushing,

2) measure where the case head is in comparison to the end of the barrel, (ie. dead flush with the end of the barrel, however many thousandths below the end of the barrel, or in the example above how many thousandths it sticks out of the barrel), then

3) do the simple arithmetic.

Let’s put some hypothetical numbers to the diagram above. Let’s say the gap is .005.” To arrive at the optimum .001″ space between the case head and firing pin bushing, the case would have to stick out of the barrel .004″.

In summary:
Gap minus protrusion equals.001″.

IF the case were, let’s say, .004″ BELOW the end of the barrel, the “space” between the case “head” and firing pin bushing it would go like this:

Gap, .005″, PLUS .004″ equals a total of .009″.

This is WAY too much of course, so you make corrections detailed below.

Our simple system of taking measurements lets you track and work out what works best for you, to include controlling the amount of interference on the case head to compensate for a less than tight barrel lockup if necessary, but you monitor and regulate it based on measurements for consistent results, not “guess and by golly.”

Note in the example above that headspace is regulated by size die adjustment so there is both contact on the case shoulder and .001″ clearance behind the case head…. ie, “head” “space.”

Another approach is to bump the case shoulder back so it does not touch the chamber shoulder, and the case rim does bottom out in the rim counterbore in the end of the barrel. In this situation, you would shim the firing pin bushing forward as necessary and remove material from the end of the barrel as needed to make that possible.

Whichever forward stopping point you choose to use, chamber shoulder or rim counterbore, you take measurements so you know what the resulting headspace is that your method is producing.

You cannot count on magazines, reloading manuals, the TC factory, the local “authority” who has “reloaded for 40 years,” or even most of the dealers and TC aftermarket custom shops.

Diagrams in loading manuals don’t seem to really help get the concept across.

Most gun writers themselves don’t seem to comprehend it.

If the factory understands anything other than SAAMI steel headspace gauges, it does not show, nor are they helping you understand and work with it.

The “local authority” who has double slammed the barrel shut for nearly 40 years certainly is no help, nor is the guy who has worked mostly with fixed barrel bolt actions going to be any help.

And some of the worst offenders putting out erroneous information are some of the custom barrel makers. These are usually the ones leaning on headspace gauges for everything.

In fact, when it comes to the TC and NEF Handi-Rifle type break open guns, the best thing to do with steel headspace gauges is toss ’em in the trash.

They are meaningless, and misleading at best. A “gauge” means nothing to you at all when you can take the measurements yourself and KNOW exactly what the headspace is WITH THE ACTUAL AMMUNITION IN THE CHAMBER.

It is the space between the actual cartridge case head and the breechface you are concerned about, not a steel gauge that may be substantially different from the actual ammo you are shooting.

So don’t go waste money on steel gauges. You don’t need them, and you don’t want them. After you have worked with our Headspace Indicator you will understand why.

Here is a perfect example of why you cannot rely on steel gauges….click on this link and see why you must measure the headspace produced by the ammo you are firing.

STOP RIGHT HERE!
CLICK ON THE LINK ABOVE. ONLY ABOUT 1/4 OF YOU READING THIS PAGE BOTHER CLICK ON THE IMPORTANT PAGE LINKED TO ABOVE!
(Gotcha! The site statistics page does not lie. Now go back and see it.)
It is a clear cut example why you need to be conscious of headspace shooting factory ammo as much as or even more so than those who reload!

Whether you shoot factory ammo or reload makes no difference. You still must KNOW what the headspace is in any given barrel and frame combination.

You will be able to identify excess headspace with either factory ammo or your reloads. If the headspace is excess with factory ammo, anything over .006,” you have grounds to exact a remedy from the manufacturer of the barrel or the ammo manufacturer or both.

Excess headspace is the cause of many misfire situations and eratic ignition which produces poor accuracy.

No headspace, meaning the case head is hitting on the breechface when you close the barrel, can cause the barrel to not close all the way. This has been a major cause of misfires with Contenders since the first day they were produced. Or, with Encores and G2s, it prevents the hammer from cocking when the barrel is not closed all the way.

The issue of headspace is simply about making sure ammo fits the gun.

This should not be a strange concept. However, believe it or not, ammo that fits right is more likely to work right. Imagine that.

OK. Are you ready? Here goes!
Put your thinking cap on and hold on for the ride.

What IS headspace?

It IS what the word says.
It is “space” between the cartridge case “head” and the breechface, ie., “head” “space.”

The term is tossed around loosely all the time and presumed to be something you have to use a “headspace GAUGE” to measure, which is not only far from the situation, but also grossly misleading.

WATCH OUR YOU TUBE VIDEOS ABOUT HEADSPACE & BARREL TO FRAME GAP.
Click on this link to see a quick demonstration of how to measure the barrel-to-frame gap properly and how to calculate headspace.

Repeating, “HEAD,” as in cartridge case HEAD, “SPACE,” as in the space behind the head,

or the distance from the case head to the breechface.

In the TC guns, it is the distance from the case head to the firing pin bushing in the breechface which actually protrudes out from the frame a few thousandths.

This is what headspace is, and it is very easily observed and very easily measured.

Headspace is NOT a length, either!
You read it all the time, everywhere, such as “…. the headspace of the .300 Win. Mag. is .220”.

Talk about screwed up bs! That .220″ figure is the LENGTH of the cartridge from the case head to the top of the cartridge belt dimension. It is used to gauge the depth of the chamber. BUT .220″ is NOT the “space” between the cartridge case “head” and the breech face….ie, NOT “head” “space.”

OR, take the .30/06. The steel gauge used to gauge the depth of the chamber is 1.940″ from the head of the case to the midpoint on the shoulder. Everywhere you go, you read or hear, “The headspace of the .30/06 is 1.940″.
NO…. THE 1.940″ DEPTH OF THE CHAMBER IS NOT HEADSPACE. IT IS THE STANDARD MINIMUM DEPTH OF THE CHAMBER. PERIOD!

Those depths of chambers tell YOU nothing at all about where the case head is in relationship to the breech face in YOUR given barrel, ammo, and frame combination.

Are we clear on this matter?

Do you get the point?

HEADSPACE IS NOT A LENGTH INTO THE CHAMBER!

What Headspace Is NOT…. It is not the barrel-to-frame gap. Click Here

Headspace is NOT the distance from the end of the barrel to the breechface, as is so often said erroneously.

The distance from the end of the barrel to the breechface has NO bearing whatsoever on headspace, and this gap, referred to as the barrel-to-frame gap, also has absolutely NO bearing on the quality or function of the barrel. And contrary to statements by at least one purveyor of custom barrels, there is NO optimum gap for accuracy. It can be a little, or it can be a lot, as much as 1/8″ and still have absolutely no bearing on accuracy.

While to some it may be more esthetically pleasing to not be able to see daylight between the closed barrel and breechface, the amount of the gap has no bearing whatsoever on the quality of the barrel, the function of the barrel, or the headspace.

In fact, there SHOULD be some gap between the end of the barrel and the firing pin bushing. If the barrel hits on the firing pin bushing, it can do two things:

1) It can prevent the barrel from dropping into the frame far enough to allow the barrel to close all the way and thus prevent it from firing, and

2) we are finding that if it is not hard contact it can often cause severe vertical stringing of shots that ruins accuracy. In other words the end of the barrel is just bumping randomly on the firing pin bushing during the firing cycle.

Both the barrel not closing all the way and vertical stringing related to the barrel hitting on the firing pin bushing should be corrected by facing material off the end of the barrel via filing, lathe turning, or milling. There should be at least a few thousandths clearance between the end of the barrel and the firing pin bushing. Do not worry about taking off too much material. The barrel-to-frame gap can be up to 1/8″, approximately the depth of the extractor slot. While this is extreme, and it is not necessary to remove this much material, the point is that the amount of gap has no bearing whatever on headspace unless it is a rimmed case, and you take off more than about .050.”

A gap of .003 to .005″ is ok both esthetically and functionally, but taking off more than this does not hurt anything either.

To set up a barrel and frame combination so that there is no gap or minimal gap can be a gross mistake, one discovered when the barrel is later installed on a frame whose hinge pin holes are somewhat closer to the breechface than the frame the barrel was set up on.

HINGE PIN HOLE LOCATIONS DO VARY FROM FRAME TO FRAME. I have only found about a .003″ variance from frame to frame while some report as much as .008″ variance. But once again, a barrel that hits on the firing pin bushing on one frame may not close on the next frame if the hole in that frame positions the barrel closer to the firing pin bushing.

Background behind the Bellm Headspace Indicator

The Bellm Headspace Indicator was developed as a result of my many years of measuring case head protrusion from the ends of barrels to determine the proper depth to ream chambers and is THE EASY WAY for the average reloader and real pro alike to quickly and accurately determine EXACTLY what the headspace is with his resized cases, rimfire ammo, and with factory ammo as well, of course!

For years I used a depth micrometer in the shop for measuring how far a case or headspace gauge protrudes from the chamber, but after all these years a depth micrometer is still rather touchy to get an accurate measurement with while balancing it over the end of a case head and being very careful to sense when the quill of the micrometer actually contacts the end of the barrel. Getting lazy, or smarter in my old age, I started using a dial indicator set up on the cross feed of the lathe to measure how far the case heads stuck out. But few people have a lathe handy for doing this.

For about a year I toyed with the idea of making this task simple and accurate for the amateur and real guru alike. I think I have “bingoed,” and once you try it, I think you will wonder how on earth you ever managed with the old ill-infomred methods we all used for years.

Keep this TIP in mind as you read on:

You will also find that there is a “sweet spot” where the case head is neither too far from the breech face of the frame or jammed forward by the breech face when the barrel is snapped shut. This “sweet spot” is where mysterious Contender misfires disappear, failure to cock with Encores and G2s disappears, case life improves, and where the gun shoots its best. It will also prevent many extraction problems that result from cases improperly sized being crammed into the chamber and then not readily extract.

The bottom line is that chambers and throats have to be cut to a certain depth. But it is YOUR responsibility to make sure your ammo fits the chamber.

Understanding what to do and being able to take the measurements tells you exactly what you have so you can get it right.

The Bellm Headspace Indicator lets you take the same measurements I have to take.

You expect me and anyone else cutting a chamber to cut it to a certain depth, and for good reason. Things have to fit right to work right.

So how much sense does it make for you to either cram a round in that is too long in the body and sticks out of the barrel too far OR falls too far down into the chamber?

Either is bad. Both cause problems. I am expected to do my part, now I am enabling you to intelligently do your part.
It is very, very simple and easy. And, frankly speaking, if you are not willing to take these measurements and take a few simple corrective measures on your own as the need arises, sooner or later you will be happier dumping the interchangable, break open barrel systems in general and going back to fixed barrel guns such as bolt actions.

That, my friends, is the cold hard truth.


No gizmos are needed! No comparators, no modifed cases, no Stoney Point type equipment is needed.

For starters, put them away if you have them, and if you don’t have them, save your money, along with a lot of frustration, until you understand headspace and what goes on in a chamber.

With the Bellm Headspace Indicator you also measure the distance from the ends of the rifling to the breechface, the firing pin bushing, once again eliminating the need for other measuring devices to determine rifling-to-breechface length, ie, overall cartridge length based on bullet contact at the riflings.

Using the barrel itself as the only TRUE gauge for the ammo and frame you are working with, you use the Bellm Headspace Indicator to also measure bullet seating depth. Starting with a bullet seated out a bit far, you measure how far the loaded round sticks out of the chamber, then seat the bullet deeper until the loaded round’s case head-to-end-of-barrel reading is the same as with an empty case with its known headspace produced.

The barrel IS your gauge. You do not need any other gauging device or gimick to do this. Nor do you have to buy anything else to go from one chamber to the next. You don’t even need a caliper or micrometer, and there is no error to be made transferring information from one tool to another. You simply and accurately measure what occurs in YOUR chamber.

No gadget that measures a length on a case, case body, rim, or belt measures headspace. It can measure only ONE parameter, a length (or a thickness) but this is NOT headspace. You must know where the breech face (firing pin bushing) is in comparison to that length.

I will make an exception to the above, and that is to verify the consistency of the headspace from round to round using a comparator or the measuring device like the one sold by Innovative Technologies to save time reloading.

Innovative Technologies. Click here for more info. (See also their belted mag size die that corrects the bulge just above the case belt not sized completely by some size dies. This bulge can cause problems preventing the case belt from making contact in the chamber like it is designed to do.)

Redding and others make measuring devices for use in reloading presses, but the Innovative Technologies gauge stand offers a wider range of uses with nothing more to buy and is preferred.

Without taking the barrel off the frame and checking every round, you can use this indicator stand to identify those cases that have the shoulder pulled forward excessively by the size die expander ball.

When resizing cases you note that some cases come out of the size die harder than others. Well, guess what. That strain on the neck going over the expander ball also pulls the shoulder forward.

If you doubt this effect simply remove the decap stem and measure the headspace created by a case sized without the decap stem/expander ball installed and compare its body length to cases sized with the decap stem/expander ball installed.

I suggest using this type of indicator & stand but with body length verified by cross checking the actual headspace of a round in the chamber. It also serves as a short cut setting up size dies once the headspace produced by a given round is clearly established from the barrel and frame combination measurements, but should be verified from time to time and as loads/pressures change.

Changes in the amount of frame flexing due to changes in pressures result in changes in actual body length the size die produces.

Also, case shoulders of all rimless bottleneck cases with long sloping shoulders collapse to some degree under the impact of the firing pin. The result is a case body .003″ or more shorter than before firing if the pressure is not high enough to stretch it. Decreasing the headspace produced by shorter cases will result in less stretching when fired again at higher pressures that will stretch it.

Due to:
1) case shoulder collapse from the firing pin impact and
2) stretching of the case along with frame flexing under high pressure,

3) cases fired in the break open guns do NOT represent the actual shoulder to breech face dimension of the barrel and frame combination, and

4) therefore, cannot be used with this measuring device to establish a headspace baseline case body length in the break open guns, nor

5) do moderate loads fired in rigid fixed barrel guns create a true representation when the case shoulder collapses under the firing pin impact and pressure is not sufficient to stretch the case all the way back to the breechface.

Take your measurements from the barrel, frame, and ammo combination FIRST, then use the indicator stand to monitor your work reloading.


CRITICAL INFORMATION! PAY ATTENTION!

CASE SHOULDERS COLLAPSE WHEN THE FIRING PIN DRIVES THE CASE FORWARD!

With the exception of sharp shouldered cases such as the 40 degree Ackley-type cartridges, THE IMPACT FROM THE FIRING PIN COLLAPSES CASE SHOULDERS FROM .003″ TO .006″ TO AS MUCH AS .010″ TO .012″ ON THE FRAIL SHOULDER OF ROUNDS LIKE .35 REMINGTON!

You can very easily demonstrate this for yourself! It should be as obvious as the proverbial train wreck……, however, few shooters are aware of it. Even though evidence of it shows up, it is nearly always ignored.

DO THE FOLLOWING:
1) Remove the extractor.

2) Chamber an EMPTY resized and PRIMED RIMLESS bottle neck case.

3) Measure where the case head is relative to the end of the barrel. For example, let’s say it sticks out of the barrel .003″.

4) Fire the primer.

5) Open the barrel. With no extractor to move the case, you will find the case head is now anywhere from .003″ to .006″ FORWARD of where it was before you fired the primer.

The long sloping shoulders and/or shoulders with a very small shoulder area collapse the most.

Quick examples are:
.308 Win., about .003″
.35 Whelen, about .006″
.35 Remington as noted above, about .010″ to .012″
.280 Ackley Improved, usually less than .001″

Thus if headspace is a bit on the generous side, say more than .003″, the instant the firing pin drives the case into the chamber deeper, headspace is increased to or in excess of the .006″ that is generally accepted as maximum.

You will also find that if you start with published starting loads and work up, shooting without the extractor the cases will stay forward in the chamber and not even move back to fill the barrel-to-frame gap until loads approach maximum. Tapered cases will move back at lower pressure than will straight walled cases like .308 Win. .308 Win. cases will not move back until nearly published book maximum loads.

This is one of the main reasons why you cannot rely on a fired case to determine case body length to establish a baseline for correct headspace.


The Bellm Headspace Indicator is made for both Encore and Contender/G2 barrels.

The Bellm Headspace Indicator base is made double ended, with one end at .810″ for Contenders and the other at 1″ for Encores. To go from Contender to Encore mode, just loosen the set screw in the side of the base and insert the dial indicator’s stem from the opposite end.

Matching up the diameter of the appropriate end of the indicator base with the breech end of the barrel positions the quill of the indicator over the solid head of a case in the chamber, just outside of a large rifle primer pocket.

You hold the indicator base on the end of the barrel with your finger and thumb gripping the base and barrel togehter. This keeps the base centered over the end of the barrel while the offset indicator quill contacts the head of the case, missing both small and large primer pockets. It is set up to work this way with any cartridge from .22 Hornet up through the belted magnums and .404 Jeffery type rounds.

It is also used with rimfire barrels, but the base must be moved over slightly to position the indicator quill over the head of the case.

The ends of the base are recessed .1″ so that when positioned on the end of the barrel with a case in the chamber, the case can project out of the barrel while the base itself is sitting flat on the end of the barrel.

(Note: Early production bases were recessed only .050,” but to make it easier measuring throat length, we went to .1″.)


Let’s start. First measure the barrel-to-frame gap.

Using a common set of feeler gauges you first determine what the gap is between your barrel and frame’s breechface by closing the barrel on successively thicker blades placed in front of the plug in the breechface until you find the blade that is gripped by the closed barrel. The thickness of the thinner blade just below the one that is tight in the gap is the gap’s measurement you use. Make note of this amount.

If you use the barrel on more than one frame, you should make a note of the serial number of that frame since the barrel-to-frame gap will vary some from one barrel to the next and from one frame to the next.

Due to normal acceptable manufacturing tolerances each barrel and frame combination can be different.

I usually scribe or stamp the barrel-to-frame gap on the bottom of the barrel lug for reference later when switching from frame to frame or as a means of monitoring a frame for signs of stretching. An increasing barrel-to-frame gap is an indication metal is moving, meaning the frame is stretching.

The barrel-to-frame gap measurement must be taken at a point directly above the chamber, between the firing pin bushing and the end of the barrel. Because the firing pin bushing sticks out of the frame a few thousandths, you cannot slide the blade in. You must close the barrel on the blade.

The thinnest blade in most feeler guage sets is .0015,” while some go to .001.” If the barrel closes on the thinnest blade, call the gap Zero.

To use the Bellm Headspace Indicator itself,
first loosen the knurled knob at either 10 o’clock or 2 o’clock. This knob locks the dial face in position.

Next, place the base on a flat surface such as a smooth table top. With the indicator quill contacting the surface the base is sitting on, turn the dial face so the hand lines up with “0.” Lightly tighten the dial face lock so the face will stay where you set it.

The pointed tabs over the dial face are for setting upper and lower limits of measurements. Normally, for what we use these indicators for, we do not use them, but you may.

Remove the barrel from the frame, and if the extractor sticks out of the barrel too far, you may have to remove it also by driving out the roll pin that holds it in. Punches are in the Tools section of the store. Tools

With the indicator zeroed and then placed on the end of the barrel with a sized case in the chamber, it will then show exactly whether the case head is below the end of the barrel, flush with the end of the barrel, or by how much the case head sticks out of the barrel. Just be sure to always watch what direction the indicator needle is moving, up or down, in relationship to your “zero,” ie, the end of the indicator base/end of the barrel.

Note that the case head should ideally never sit below the end of the barrel,
even if the barrel is tight on a .001″ or .0015″ feeler guage blade, which is usually the thinnest blade in a set. With a really close barrel-to-frame gap, the case head should be flush with the end of the barrel and never more than about .002″ below the end of the barrel. This would result in an actual headspace of about .003″.

If it is more than .002″ below the end of the barrel, you will need to shim the firing pin bushing forward, BUT since there is no room to move the bushing forward, you will have to face off the end of the barrel to make room for the bushing.

Nor should the case head stick out more that what the gap actually measures. The ideal is to have the case head stick out about .001″ LESS than what the gap measures.

Ie., if the gap is .003,” then have the heads of sized cases stick out .002.” This gives a heaspace of .001.” Many folks don’t understand what headspace is. Here you see it. It is the actual distance, space, between the case head and the breech face. If the case head sticks out MORE than what the barrel to frame gap is, this is referred to as “negative headspace.” Having case heads stick out more than what the gap measures causes all sorts of problems, and getting cases sized right cures the vast number of problems that plague shooters of break open guns.

Summary of Headspace Conditions:

If the case head is perfectly flush with the end of the barrel, the headspace will be what the barrel-to-frame gap measures.

If the case head sticks out of the barrel any at all, the headspace will be the barrel-to-frame gap MINUS how much the case sticks out of the barrel.

If the case head falls below the end of the barrel, add the distance from the end of the barrel down to the case head to the barrel-to-frame gap measurement. This total is the actual headspace.

If the headspace is more than .006″ it exceeds SAAMI industry standards, and the condition should be fixed.


Headspace as it relates to misfires:

The greater the headspace, the more distance the firing pin has to drive the case forward in the chamber until it comes to a dead stop and the firing pin can expend its energy denting and firing the primer. If too much energy is lost moving the case forward, there may not be enough energy remaining to fire the primer even though the primer may appear well dented. Thus, minimal headspace is mandatory not only for best accuracy, but even useable accuracy and reliable functioning of the gun.

If the case head sticks out of the barrel more than the barrel-to-frame gap measures, it prevents the barrel from closing all the way and the locking bolts from traveling far enough under the frame’s “locking table” for an adequate lockup.

In Contenders, the result is that the hammer block is not fully released so it can freely drop fast enough to clear the hammer. The hammer knicks the top of the hammer block and even though it may still dent the primer, too much energy may be lost hitting the hammer block to still fire the primer. THIS IS ONE OF THE MAIN CAUSES OF CONTENDER MISFIRES!

In G2s and Encores, incomplete lockup due to the case sticking out too far prevents cocking the hammer.

Until now, there has been no convenient way for the average person to accurately measure the distance the case head sticks out the barrel.

Worse yet, the vast majority of Contender and Encore shooters don’t have the foggiest notion about how to adjust the size die to get the correct headspace. And the travesty is that those who do often attempt to use SAAMI gauges, which in the real world is no where nearly correct when hinge pin holes in barrels and frames vary as much as they do.

You HAVE to first know what the gap is then MEASURE where the case head is situated relative to the end of the barrel. This set up lets you do it accurately and easily, just like I have to do when cutting the chamber and throat length to the correct depth.

You expect the chamber to be cut to the right depth, but unless you can take the necessary measurements, you will never consistently make the cases or loaded ammo the right length. The fact is that with handloaded ammo the depth of the chamber is not important IF you make the ammo fit the chamber. Precise measurements let you do this.

And if you shoot factory ammo, you still need to measure the actual headspace since it is very common to see a “stacking of tolerances” that create really excessive headspace resulting in misfires and poor accuracy due to eratic ignition.

A combination of a chamber on the deep end of the .006″ tolerance limit, factory ammo on the short side of the .006″ tolerance limit, and a frame hinge pin hole on the forward side of tolerances can result in headspace well over .010.” And with belt height variations on belted magnum ammo, headspace can be well over .016.”


What happens when a round is fired.

First,

the firing pin has to drive the case forward in the chamber until it comes to a solid stopping point. This can be the case shoulder, the case rim, or the belt on a belted magnum round.

It takes energy to move the round forward. The farther it has to be moved by the firing pin, the less energy is left to fire the primer. If the distance is too great, the primer recieves a softened blow instead of a brisk strike….. like getting pushed with a pillow versus a quick jab with a stick.

If the strike from the firing pin is too soft, primer ignition may be eratic or it may not ignite at all even if it is dented pretty well. While a stronger hammer spring will ususally stop misfires due to excess headspace, the stretching of the cases that occurs can cause them to fail quickly if they are reloaded.
Bellm Extra Strength Encore and G2 Hammer Springs

Next,
when a round is fired, the break open actions flex from the force coming out the chamber end of the barrel. How much the frame flexes depends on how much thrust there is from the case head pushing on the breech face. High pressure, large diameter rounds like 7mm Rem. Mag. and .300 Win. Mag. exert the most force on the frame, and the smaller diameter and/or lower pressure rounds like .22 Hornet exert the least. Of course the rimfires exert the least of all, but are not what we are concerned about here.

There is a certain amount of “play” in the locking bolts, the hinge pin, and the general fit of the barrel in the frame. Plus, the long, thin slab sides of the TC frames are somewhat springy compared to a bolt action rifle where the locking lugs on the bolt are close to the end of the barrel.

Thus, when these break open guns are fired and the barrel and frame flex, the cartridge case moves and/or stretches back. While the frame returns to its normal “at rest” dimensions, it does not force the case back to its original dimensions and leaves it too long to go back in the gun without some force on the case head.

This extra length must be removed or the breech will be cramming the case in and up in the chamber the next time it is reloaded and fired. Size dies must be adjusted to push case shoulders back the correct amount to produce a protrusion of the case head that is not greater than the barrel-to-frame gap measures, and preferrably just protruding .001″ LESS than the barrel-to-frame gap measures.

Resizing to bring a case back to the correct protrusion from the end of the barrel can ONLY be accomplished by full length resizing. If the full length size die will not push case shoulders back far enough when the shell holder is run all the way to the bottom of the die, then the die must be shortened from the bottom end until it will move the case shoulder back where it needs to be.

While neck resizing may work at lower pressures and for just a resizing or two, sooner or later cases will become too long and have to be full length resized. Any attempt to push case shoulders back with a neck sizing die can result in the cases bulging outward below the shoulder and sticking in the chamber.

Correctly adjusted full length resize dies are the only way to go for reliable functioning.

Here you have a round sticking out of the barrel less than .004″, correct for a .004″ barrel-to-frame gap.

Note there is no extractor in the barrel so that when it is fired the case head will be in the same place it was after firing.

After firing and with no extractor to move the case you can measure how much more the case head sticks out of the barrel than the gap measures.

Here you can plainly see it is sticking out .006″ as indicated on the dial, .002″ MORE THAN THE GAP MEASURES.

With no extractor in the barrel, the case head remains wherever it was after the shot. Removing the barrel from the frame and measuring the protrusion of the case head, you can see that with a .004″ barrel-to-frame gap, this mild .30/06 load leaves the case head sticking out of the barrel .006″, which is .002″ more than the gap.

This means that if you do not bump the shoulder back at least .003″ in this particular situation, the frame will be jamming the case into the chamber when fired the next time.

****You not only need to remove this excess BODY length (not to be confused with overall/trim length) by running the case farther into the size die, but you need to know HOW MUCH change you make. This means you must take measurements of how far the case sticks out of the chamber. It must not be more than the gap measures and ideally should be .001-.003″ LESS than the gap measures, but it should NOT fall below the end of the barrel.

As stated above, you can NOT determine headspace by measuring the length of a fired case!
Period. Amen. End of Conversation. It cannot be done with any accuracy at all.

There is a school of thought carried over from the bolt action arena where size die adjustments are based on duplicating fired case body length….. which is totally bogus with the break open guns!

Due to variances that occur in THIS mechanism it can NOT be done. To think otherwise is simply missing some important facts.

Please excuse me if this comes across as a tirade, but I am tired of trying to correct all the misinformation put out by a number of “experts” including much of the firearms industry as a whole.

Facts are facts, whether you personally have paid enough attention to the right things to see it yourself or not.

You can easily see it IF you will just look.

If any of this offends you, it is better you take offense now and get rid of the system if you won’t accept and deal with the facts,

OR, lay your problems and arguements at someone else’s feet. I am developing zero tolerance for stodgy, bone-headed stupidity.

I’m here to fix the lack of knowledge and don’t keep a baseball bat handy to fix stupid.

Here are the FACTS!
All you experts out there pandering erroneous ideas…. open your eyes!

Pressure level, case shape, and brass thickness control how much the case moves back in this springy mechanism.

  • With a full normal max load in most rounds as clearly shown above, the frame flexes, and play at the locking bolts and hinge pin allow the case to move back or stretch back MORE than the barrel-to-frame gap measures AT REST.,
  • Loads light enough to NOT move the case back will leave the fired case FORWARD in the chamber, giving a false indication that the distance from the shoulder to the firing pin bushing is shorter than it really is.

All you have to do is remove the extractor and start measuring and shooting.
With no extractor to move the case, you can see and measure exactly where the case head is both before firing and after.

You will find for example that straight wall cases like .308 Win. are driven forward by the firing pin at least several thousandths, and it is not until nearly full maximum loads that the case even comes back even with the end of the barrel or touches the firing pin bushing.

On the other hand, more tapered cases like .30/06 & .270 Win. especially will move back and protrude MORE than the at rest barrel-to-frame gap measures.

The bottom line is the case head can end up anywhere after the firing cycle has completed.

It can end up WELL below the end of the barrel, FAR away from the firing pin bushing.

It can end up sticking out substantially MORE than the barrel-to-frame gap.

Or, only by coincidence only, it can end up ON the firing pin bushing without enough force to flex the mechanism and thereby accidentally giving a true reflection of the actual distance from the shoulder to the firing pin bushing.

These comments are geared to bottleneck cases primarily because this is the realm where most errors occur.

When you measure a fired case from shoulder to headstamp, the fact is the case may be much shorter than actual dimensions in the gun itself, or it may be substantially longer.

It is not only a waste of time and money to attempt to measure headspace based on a fired case, it is simply gross ignorance of the gun and what actually happens when the gun is fired. To cling to that mindset is gross stupidity that is greeted rather brusquely when you lay your problems related to it at my feet.


Correcting Excess Headspace.
If there is too much space between the case head and the breechface there are ways to correct it. This can occur with factory ammo, new brass, or brass that has had the shoulders pushed back too far.

Basic methods of correcting excess headspace

 

  • Shim the firing pin bushing forward, which may also require removing some material from the end of the barrel,

 

Encore Headspace Shims
Contender/G2 Headspace Shims

 

  • Blow case shoulders forward by first creating a shoulder on the neck for a headspace point….successful if done right and there is ample support against the blow of the firing pin,
  • Make cases by necking down new cases with larger diameter necks, such as making .30/06 cases from .35 Whelen brass,
  • Blow case shoulders forward by using a compressed charge of slow powder behind a bullet jammed hard into the rifling. This is for the advanced reloader and while 100% effective, can be tricky, even dangerous if you don’t think your way through what you are doing,
  • Bend case rims forward on rimmed cases,
  • Rechamber to a longer cartridge, but get the chamber cut to the correct depth for proper headspace,
  • Assuming headspace is over .006″ with factory ammo, return the barrel and frame to the maker for replacement.

 

Special note from Redding regarding size die adjustment:
Frequently shooters are not able to push shoulders back simply because the shell holder is not hitting solidly on the bottom of the size die.

In other words, if your resized cases stick out of the chamber too far, be sure the shellholder presses solidly against the bottom of the die before you decide the shoulders cannot be pushed back as required. Flexing of the press can leave a gap between the shell holder and the bottom of the size die. So make sure there is no gap IF it appears the size die is leaving the cases sticking out of the chamber to far.

Mike Bellm: If cases still stick out too far, then it may be necessary to remove material from the bottom of the die so as to permit bring the shoulder inside the die closer to the shell holder/headstamp of the case.

A VERY USEFUL TIP:
When adjusting size dies and seating dies, use the threads on your reloading dies like a micrometer.

Think this through. You will find it invaluable.

A common micrometer is based on a 40 pitch thread (40 threads per inch), meaning 1 inch is divided into 40 parts. That is why the marks around the drum of a micrometer only go to 25. One full turn, ie, one thread, equals 1/40th of an inch, or .025.”

Size dies have a 14 pitch thread, so dividing 1.000″ into 14 parts gives .071″ movement up or down with each full turn.

One half turn moves the die up or down .0355.”
One half of a half turn, ie, 1/4 turn moves it half of this, .0175.”
One half of 1/4 turn, ie, 1/8th turn, is half this, .0089.”

In the process of adjusting your size die, you can see that once you are down that close, the dial indicator & base will let you tweak the die very precisely for the final protrusion of the case head from the end of the barrel that you are after.

Measuring seating depth:
Use the thread pitch of the seat stem in the bullet seating die like a micrometer just like we described above for the size die.

You do not need to buy any gadgets or gimicks to measure seating depth. YOUR barrel IS the GAUGE. Here is how it works.

As with headspace, you MUST know what the barrel-to-frame gap is. And you must either have the barrel off the frame or the extractor removed if the barrel is left on the frame.

Make sure you have your cases sized correctly so that they protrude from the chamber the correct amount. Then seat a bullet out farther than anticipated. Drop the round into the chamber, and measure how far it sticks out. The indicator base is counterbored .100″ deep for clearing the protruding case head, so you want to work the seating depth down to where the case sticks out of the chamber less than .100.” (Early production indicator bases were counterbored only .050.” We increased this depth for convenience taking seating depth measurements.)

Establish what the thread pitch is on the bullet seating stem. You can get a thread pitch guage from a hardware or automotive store, or you can measure one inch of thread and count the number of threads in that inch.

Let’s say you are using an RCBS seating die with a 1/4″x28 thread pitch. Divide 1.000″ by 28 threads per inch, and you get a value of .0357″ per one full turn of the seat stem up or down. Half a turn is .0357″ divided by 2 equals .0179.” A fourth of a turn is .0089,” and an eighth of a turn is .0045.” You should not only be able to estimate a half of a fourth, 1/8th turn, but also guesstimate finer adjustments still.

See how precisely you can tweak the seating depth down to the point you get back to the same case head protrusion as with an empty, properly sized case?

With the bullet touching the rifling and the case head sticking out of the barrel the same amount as when empty, you now know exactly what the relationship is between where the bullet makes contact with the rifling and the breech face, allowing for .001″ headspace. Remember, if you seat a bullet out farther than this, your round will stick out of the chamber too far, meaning, you will have lost the .001″ headspace you established with a sized case.

Use the values you established for your seating stem to determine how far off the riflings you have seated bullets.

You might want to keep one round with the bullet seated just to the lands and other rounds marked with the amount of either bullet clearance from the lands or, although I usually advise against it, save and mark rounds that stick out MORE than the gap. These rounds will be your gauge for adjusting the seating die if you want to engage the rifling a certain amount.

Note in regard to eratic measurements of bullet seating depth:
If your bullets are canted in reference to the case body or neck, they will not seat straight in the throat where they contact the ends of the rifling, and thus they will bind up and not give uniform measurements. Smoking or inking the bullets will also show whether the riflings are touching uniformly around the ogive of the bullet. You can get an inexpensive dial indicator stand to position an indicator over your cases laid in a groove, such as a “V” block (though a groove in a block of wood works also, for example). Turning the case in the groove, the indicator is used to measure “runout,” or misalignment of the bullet. If you find much runout, then you need to take steps to cure it.

However, if the bullets do not go straight into the throat of the barrel, they will bind up on their sides, and you will not get consistent readings.

Click here for graphic examples of throats misaligned with the bore.
Please DO take time to look at this so you can see just how badly throats are very often misaligned with the bore. The misalignment can be parallel to the bore, but most often the chamber and throat are at an angle to the bore.

Please excuse the caustic comments on this page, but there are some really misguided folks cutting chambers that simply don’t have a clue what they are doing. Any fool can go buy a reamer and cut a chamber, but as with any tool the end product depends largely on HOW the tool is used.

Unfortunately too many of you are paying the price for someone’s ignorance.

Eratic protrusion of sized cases from the end of the barrel:

Note that as with bullets seated canted in the case and giving eratic readings, you can also get very eratic readings from your sized cases due to the expander ball pulling the case shoulders forward an inconsistent amount, so do this:

1) Taper, smooth, and polish your expander balls, or get the elliptical or carbide types.

2) Clean and lube the insides of your case necks before sizing.

In any event, the headspace indicator will measure and identify variations in headspace caused by the expander ball pulling the shoulders forward inconsistently.

Measure the protrusion of a number of sized cases, and you will find this is very true. Simply setting the lock ring on a size die does NOT give consistent headspace. Sorry to bust your bubble if you think your cases are all the same.

As an interesting experiment, measure the protrusion of a bottle neck case sized with the expander/decap stem in place, then remove the expander/decap stem, run the same case through the size die again, and measure its protrusion. If there is much tension/drag at all on the expander ball, it will in fact pull the case shoulder forward. How much depends on just how hard it is to pull the expander back through the neck.

If you sort out cases that give exactly the same amount of case head protrusion, you will also very likely find groups tightening as a result.

Other factors the Headspace Indicator can determine.

1) A very common problem occurs, and, again, it is one the Headspace Indicator will precisely identify. This is the fact that many size dies are purposely made too long inside so as to NOT push the shoulders of the cases back past SAAMI dimensions. Particularly if the chamber is on the maximum side of depth tolerances or if the expander ball pulls the shoulders forward too much, the size die may not push the shoulders back enough to give the proper case head protrusion less than the barrel-to-frame gap measures. In this situation, the size die must be shortened, either by grinding some off the bottom or “facing off” the end of the die with a carbide lathe tool in a lathe. The tops of shell holders can be taken down for the same result, but this weakens the shellholder and makes it more prone to stripping out. Thus it is best to shorten the size die itself and polish the internal edge as required so there is not a sharp edge that will scrape brass at the mouth of the die.

2) Another item you can measure is the out of square condition of the case heads caused by the end of the barrel (and/or chamber) not being square to the breach face. Rotating the indicator base on a chambered round will show the degree to which the case head is out of square to the end of the barrel, and positioning cases consistently based on the high or low point on the case head reading may also influence grouping.

(By design, Encore and Contender/G2 barrels drop into the frame below square to the breechface as clearly indicated by the fact that when barrels touch the firing pin bushing, the rub mark is ONLY above the chamber. This results in the bore and chamber line of the barrel being out of square with the breechface unless by random chance the chamber is misaligned in the right direction and by accident is square to the breechface.)

3) Monitor the relative amount of force on the frame:
We find that loads that put a lot of strain on the frame often do not shoot well. With the extractor removed, you can measure how far fired cases are protruding from the frame at various pressure levels. The more force there is on the frame, up to a point, the more the cases will stick out of the barrel when fired. You may find that cases that stick out of the barrel, say, .003″ more after fired than before shoot better than those that stick out, say, .005.” Monitoring this can be valuable information in determing “sweet spots” where a barrel shoots best.

Above a certain pressure load, the cases when fired either slide back in the chamber or if the case wall adheres to the chamber wall and pressure is sufficient, the case will stretch back to the breech face. Higher pressures will also cause the frame to flex substantially. Thus a case that perhaps sticks out .002″ before firing may be sticking out .012″ after being fired. If you shoot a barrel with the extractor removed, you will definitely see changes in the case head’s position from before and after firing. No values have been given to the amount of flexing of the frame that is permissible/allowable, but once you establish your own value, short of stretching and ruining a frame of course, you can use the headspace indicator to measure how much the frame is flexing based on how much the case head protrudes from the chamber after firing.

4) With the extractor removed, another phenomenon you should be aware of and measure is the collapse of the case shoulder when the firing pin hits the primer and drives the case forward in the chamber. You can and really SHOULD take your properly sized cases, prime them, then with the extractor removed from the barrel, fire the primer in the primed case. Opening the barrel, you can now measure just how far the firing pin has driven the case forward in the chamber.

If you push the shoulder on the case back too far, then try it in the chamber WITH the extractor installed, you may find that the extractor does in fact prove to be a headspace point even with rimless cases.

For example, removing the extractor from .35 Rem. barrels, I have found that often times they will not fire at all. The fring pin simply drives the case into the chamber without firing it, or, if the chamber is not super smooth, the fired case may remain substantially below the end of the barrel. With the extractor installed, it will fire normally since the extractor limits how far the firing pin can drive the case into the chamber.

Measuring rimfire ammo case rims for uniform thickness,

and, thus, uniform headspace.

“Mouse Gunners,” rimfire “smallbore” shooters, have sorted ammo by rim thickness for years, but now can precisely measure the actual headspace of rimfire barrels on break open guns as well as rim thickness uniformity from round to round the same as with the gauges sold separately for this job for years.

With the advent of the .17 rimfires, sorting by rim thickness could prove beneficial to this venue also.

Measuring headspace in straight walled, rimmed chambers.

The rounded tips on most indicator quills can be unscrewed leaving a square end on the quill that can be used to measure the depths of rim counterbores in the end of the barrel. This has to be done carefully so as to not twist the quill itself and bend the pinion shaft inside the indicator. You must grip the quill part only from each end, meaning, DO NOT hold the indicator body and try to unscrew the tip. You can ruin the indicator very quickly.

The depth of the rim counterbore can be extremely valuable information to have. Measure the thicknesses of case rims on straight walled cases. Then measure the depth of the rim counterbore, add the barrel-to-frame gap measurement, and subtract the rim thickness to derive the actual headspace.

As noted above, there are ways to reduce the headspace on case rims. One other method not mentioned above is to peen the mouth of the chamber at the rim counterbore. This will move metal in the bottom of the counterbore back usually a maximum of .003″ and can be sufficient to solve headspace problems very common to chambers like .445 Super Mag that are usually deep enough to cause excess headspace and early case separations.

As you can see, there are a number of things the Bellm Headspace Indicator set up can measure.

In the process, you will be able to tell precisely what is going on in your break open guns. You can get a “handle” on what produces best accuracy and what doesn’t, or in the case of frame flexing, you can establish a standard for the amount of flexing your maximum loads should produce, past which you don’t want to go, thus establishing your own maximum pressure “redline.” Note that no printed instructions are being sent with the indicator bases or complete setups, so I suggest you print out this page for reference.

If you have not gotten the Bellm Headspace Indicator Base, you really do not know what you are doing. Unless you are using a difficult to use and expensive depth micrometer, there is no way you can know. For years we guessed, if we even thought about it. Now we can get truly “dialed in.”

Stop shooting in the dark. Know PRECISELY how your cases are sized and how your bullets are positioned in the throat with the Bellm Headspace Indicator!

Order yours today!

Bellm Headspace Dial Indicator

A final comment, with qualifications:
The following is NOT the best way to do things but can be used as a
“bandaid” to compensate for loose lockup IF you do not have the lockup corrected.

IF the barrel’s lockup is on the loose side, SOME pressure on the breech face by the case head pressing against it CAN improve accuracy. But once again, too much force on the case head closing the barrel or eratic force due to variances in actual case body length will also likely result in poor accuracy.

On the other hand, measuring how far the cases stick out of the barrel and maintaining a distance that WORKS you may find a sweet spot that can only be controlled by precise measurements.

“Even a blind sow can find an acorn” applies here. IF by experiment you stumble into that sweetspot, THEN maintaining that body length consistently by measuring the body length with a separate device such as sold by RCBS and Redding, you may do well.

But once again, to try to establish this “baseline” length from a single fired case is a wild shot in the dark. You will likely only arrive at this length by accident doing it this way.

Regarding loose lockup of the barrel in the frame:

Contact me for instructions for shipping your barrel to me to correct the lockup by forging the barrel lug and recutting the slot, a process I have worked out with great success.

Mike Bellm

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More Chamber Misalignment

This is what you guys are up against when you buy a barrel or have a barrel rechambered. It is not about finding fault, it is about educating shooters and getting the performance from the TC guns that they deserve.

It is also about shooting sports in general and fair play.

When you buy a barrel you ASSUME the chamber is aligned with the bore. However, the graphic examples on this page were submitted by a customer having severe accuracy problems indicating what actually occurs.

Unfortunately, examples like these are far more common than you might think and are the main reason for inaccuracy after all the fundatmentals have been applied and failed.

Here you see the riflings do not start on the cast until about 5/16″ from the end of the chamber neck!

Here you see rifling coming back almost to the end of the chamber neck.

The bottom line is that chamber throats are something normally kept hush, hush in the firearms trade in general. Everyone talks about overall cartridge length, seating depth, freebore, and all the various words skirting around what is actually inside the barrel and what its function is.

No one is talking about throat diameter or throat alignment with the bore, yet this is the single most important aspect of the chamber.

Note that the casts have been highlighted to give clearer contrast between the lands and grooves in the cast.
Here is the main cause of chamber misalignment that is often quite severe in Contender barrels made during the first approximately 25 years of production of “drill press” chambers……25 years for “America’s Master Gunmaker” to figure out a very basic machining principle that is so vital to accuracy.


It was shortly after this picture was printed in the TC Custom Shop catalog that apparently pressure was brought to bear on Thompson Center to change their method of chambering barrels.

It was salted away but recently surfaced after the move to Olathe, Colorado.

The picture is grainy, but the middle right picture is of a barrel held vertically in a fixture with a chamber reamer held in a drill chuck poised over it.

What is wrong with this picture?
Beneath the reamer is a barrel held vertically in a fixture that references off the outside diameter of the barrel.

1) Any change in diameter from standard sets the bore off axis from the reamer.

2 ) There is at least .005″ variation in barrel diameters, sometimes more.

3) All bores have some curvature in them as drilled, warpage is induced turning the barrel blank down to size, and welding the lug on induces warpage in the bore so even if the bore is centered at the extreme breech end. At the area where the throat is, it is generally way off center.

4) Held in a drill chuck the reamer cannot follow the bore, thus

5) unless by chance a chamber was centered with the bore, you will find most chambers especially from the earlier “drill press days” dramatically misaligned with the bore as typified by the chamber casts show above.

6) When rechambering these barrels the warpage must be taken into account and corrected for. Most “gunsmiths” and many “in the trade” are not even aware of this as demonstrated by the most notable of notables who is the subject of the above casts.

The chamber casts above are from a 7mm TCU Contender barrel rechambered by one of the biggest names in TC after market barrels. Someone paid good money for this and yet as this is posted, has had no satisfaction from the shop that did it.

This is how it was handled by the shop that did the work. Their reply:

“One problem with rechambering is that the reamer will follow whatever hole is there. From the looks of it the bore is oversize or the pilot would not have let it that much off center and would have scored the bore. This is the worst I’ve ever seen. Seeing 2–300 FPS difference in velocity in T/C 7 MM barrels is normal. Seems to be interior dimension problem.
We have a 7 MM throater and about the only thing we could do is run the throater in it and see if that would help. (no charge)

Let me know what bullets and loads you were using–maybe a change would help.”

Point One: It is an easily proved fact that in the real world reamers do NOT closely follow the bore.

Several subpoints are in order.

1) Bore sizes will vary by AT LEAST .001,” and it is not uncommon to see bore sizes .002″ to .003″ on either side of standard. And, typically, reamer pilots are made at least .001″ smaller than standard bore size. So if you have a .275″ reamer pilot diameter for the 7mm barrel above, and a .277″ bore, there is at least .001″ the reamer can wander in any direction. The rifling, btw, are only .004″ high in 7mm. .276″ standard bore diameter, .284″ groove diameter. .008″ difference in diameter divided by 2 equals .004″ rifling height.

2) Heat applied to one side of the barrel welding the lug on does induce warpage in the bore.

3) Even IF a tightly fitted pilot or pilot bushing is used, hard or not, reamer pilots will still bend.

4) The barrel above was originally a 7mm TCU, very likely from the days when TC poked chambers at bores with a drill press. Many of these chambers are badly misaligned with the bore to start with, and unless the resulting runout is corrected first, the reamer will tend to follow the existing chamber.

5) It is CRITICAL that the bore be running true in the lathe and that the throat be cut as a separate, final operation independent of the body of the chamber. It is the only way to assure the most precise alignment with the bore.

6) DON’T BLAME IT ON THE BORE. YOU EITHER KNOW WHAT YOU ARE DOING OR YOU DON’T. BUT DON’T MAKE THE CUSTOMER PAY FOR YOUR DEFICIENCIES.

(I am not talking out of both sides of my mouth. Reamers will try to follow the existing hole, yes, but if there is substantial runout, the pilot cannot overcome this. Ie, it is the runout in the original chamber that is much of the problem.)

Point Two: Oversize bore or not, there is no excuse for misalignment of the throat with the bore….. and then not stepping up to the plate to correct it, either with a viable rechambering option or with a replacement barrel.

Point Three: Creating a longer throat is not the answer.
It will result in a long “freebore,” jump to the riflings, while still having a substantially misaligned area in the throat.

Point Four: Throwing a different load at the barrel is not the answer.

The problem should be as obvious as a train wreck. Starting the bullet into the bore cock-eyed and creating an out of balance bullet is not going to be corrected by a different load.

Point Five: We all make mistakes, but over the years should be learning better ways to do things.

.221 Fireball TC factory chamber. Photos provided by the same customer.

Note that the rifling come all the way back to the chamber neck.

In this photo, you can see that the rifling at the top of the cast start at about 1/8″ from the chamber neck.

This shot shows more of the angular view of where the rifling start and stop.

The .221 Fireball barrel is to be sent back to TC.

What do you do?

First, become aware of the importance of throat alignment and do not suppose that just because it came from the factory or it came from a high priced shop that it is right. Any fool can buy a reamer and poke it at a bore. Never assume that a big name and a high price is any assurance the chamber and alignment are right. I have seen examples as bad as the above even done by some of the most renowned benchrest gusmiths.

You can look into a throat and see much of the misalignment once you know what you are looking for. And as you can see, a chamber cast will confirm alignment or misalignment.

Don’t take it. Pass the error back to the originator. If you get no satisfaction, I strongly recommend a small claims court filing. Just the mention of which has opened the ears of TC’s personnel and obtained their fullest cooperation.

If you do nothing, you will continue to be taken advantage of. If you hold their feet to the fire, they will begin to see the light, hopefully respond with more responsible chamber work to start with, and be more responsive when there is a problem.

The sword cuts both ways. If you have a barrel I did with throat misalignment, please bring it to my attention also, because based on what I have learned over the years, I am sure I have some chamber throats out there with misalignment sufficient to undermine accuracy also. But during the last 15 years of both chambering and rechambering, I have made ever improving strides toward perfecting the throats I cut.

Favorable outcome of the .221 Fireball sent back to TC:

The owner of the .221 barrel sent pix of the chamber casts to TC along with the barrel, and they DID replace it with a 14″ barrel.

Being an informed customer DOES make a difference. I may be too optimistic, but I think it is far better for everyone if vendors are made aware of errors and will hopefully raise their standards instead of just rolling their warranty costs back into the retail selling price.

Here is a cast from the new replacement barrel

Alignment appears to be much, much better.

Note the difference in the length of the throat. The replacement barrel has a much shorter throat. I prefer to see a longer throat like the original that will guide and support a longer section of the bullet’s shank as it enters the rifling.

The clearances in the neck area cannot give positive alignment and support of the bullet shank, so in the replacement barrel only a very short section of the bullet shank is supported.

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You cannot depend on factory ammo

It is blind foolishness to expect all ammo to meet specs and produce correct headspace. Here is a perfect example.

Take the measurements and you will KNOW what the headspace is, then make corrections.

This gentleman complained he could not cock the hammer with a loaded .280 Rem. barrel and wondered why.
Taking a few simple measurements he could have saved himself a lot of aggravation and money paying someone else to tell him the ammo stuck out of the barrel too far and was preventing the barrel from locking up safely so the hammer could be cocked.

The frame was simply doing what it is supposed to do…. protect the shooter from firing a barrel that is not locked up adequately to be safe.

Barrel-to-frame gap measurement was essentially zero. Ie, the barrel hits on the firing pin bushing.

With the barrel off the frame, Winchester ammo stuck out of the barrel from .005″ to as much as .010,” and it is no wonder the barrel would not close!

( Missing Image Asset )

One might think on first impression that the chamber is too shallow.

NOT SO!

Here you can visually see that the .280 Rem. “GO” gauge is below the end of the barrel. Actual depth below the end of the barrel is .001″ which is perfect.

( Missing Image Asset )

In this less than perfect photo, you can readily see that the ammo is sticking up WELL above the end of the barrel.

( Missing Image Asset )

The reason is the cases are stopped by contact ONLY at the bottom of the shoulder!

( Missing Image asset )

I try and try to get the point across that case shoulders, datum lines on steel headspace gauges, and chambers often simply do NOT match at all.

Note the ink is marred ONLY at the bottom of the shoulder where it meets the body of the chamber.

When it comes to these break open guns especially, forget about steel headspace gauges! They are meaningless when you can take direct measurements from the barrel and very easily calculate the headspace.

Going to Federal ammo, the results are better, but even the Federal ammo is a bit too long.
The barrel will likely close on this Federal ammo, but with no space at all between case head and firing pin bushing, vertical stringing may result.

As this is being written, no range testing has been done yet, but will follow when Oregon weather permits.

So, which component in the system is off….. the chamber shoulder shape and location or the ammo shoulder’s shape and location?
It could be either, but it really matters little.

The important thing is to be able to recognize the problem first, then choose a corrective measure.

In this instance it is likely simply a different brand or different box of the same brand may solve the issue entirely.

It makes no sense to ignore headspace and assume it is right.

And it makes no sense to rely on steel gauges when the ammo does not always resemble the gauges, and it is so easy to tell if the headspace is off.

Back to Headspace, How To Get It Right

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No Poaching Poster Girl, Must See Her

Sorry to disappoint you. She’s certainly no babe in a bikini!¬†

This “No Poaching” sign was put up by a land owner along a road near Crawford, Colorado.¬†

Apparently this doe felt pretty confident folks would abide by it while taking advantage of its shade.

The event is for real, not fabricated, and was a perfect photo op friends managed to catch. Priceless!

Copyright D. Reagin

 

But seriously, she is the poster girl for anti-poaching awareness! 

Likewise, folks in the area near her have reported some beautiful bucks with the rack cut off and the carcass left to rot. 

Let’s all be good sportsmen, give game animals their proper respect, and not tolerate poaching.

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Bellm Triad cartridge

Bellm cartridges based on the .308 Winchester case body and .444 Marlin brass to both correct factory chamber misalignment and increase performance from the Thompson Center Contender and G2 firearms using common, standard reloading dies for easy, economical case forming and loading.

Custom chambers without the cost of custom dies!

Bellm cartridges in 7mm, .308, and .358 calibers for the Thompson Center Contender & G2 firearms with thoroughly tested and proven reloading data.

.308 Bellm, 7mm Bellm, .358 Bellm, load data, Thompson Center Contender, Thompson Center G2, rechambering

Encore No. 2 versions.

1) Use standard size die and have me open the chamber enough to be compatible with the larger dimensions of standard dies. (This may leave a more prominent bulge at the case web, and if it is going to bulge too much, I will decline opening it that far.  In that case you will have to select between options 2) and 3) below.

2) Use a small base size die for virtually no visible bulge at the web and a close case to chamber fit.

3) Use standard size die in conjunction with a .444 Marlin size die for the Advanced sizing method which leaves virtually no visible bulge at the web and allows for a quasi neck sizing operation, thus using the .444 Marlin size die only when cases have been expanded enough at the web to require running cases through the .444 Marlin size die to reduce the web diameter to near new brass diameter.

Properly adjust the size die:

Both formed and resized cases should always enter freely and protrude no more than the actual (measured with a feeler guage) distance between the end of the barrel and the breech face. The size die should be adjusted in small increments until the case head protrudes just short of this amount. On most barrels and frames, the case head should protrude no more than .002.” The case head must never come to a point below the end of the barrel. This paragraph applies to all bottle neck cases fired in break-open guns. Never attempt to “Neck size” either with neck size dies or by partial full length resizing. You may get away with it in light loads, but will incur extraction problems, misfires, and poor accuracy at the performance potentials of these cartridges. You must “bump” the shoulders back.

Advanced Approach to chamber and size dies

I prefer to have the user’s size die in hand when cutting the chamber for these cartridges in particular. The reason is that I like to keep the chamber mouth close to new brass dimensions, and many of the .308 Win -type dies will not size any smaller than about .470″ at the web. This means having to open the chamber up to the point that it produces bulgy looking swollen case heads in order for the chamber to be larger than the size die.

It recently dawned on me that most of the .444 Marlin size dies will size smaller than most all .308 Win -type size dies, back to within just a thousandth or two of new brass dimension of .465.”

Using a conventional .308 Win -type size die in conjunction with a chamber mouth that gives fired case web dimensions around .467-.468″, one can both size the case neck and bump the shoulder back while maintaining both a correct sized shoulder diameter (ie., no swelling of the shoulder as when trying to push a shoulder back with a neck size die) AND maintaining the fire formed fit at the web area. This is sort of a hybrid neck sizing.

When the web area¬† becomes expanded by loads hot enough to make it a tight fit in the chamber at this point, simply run cases through a .444 Marlin size die with the decap rod removed. Then the cases will be sized perfectly from shoulder to head.¬† For 7mm Bellm and .308 Bellm, you can use Lyman .358 Win dies which are about $20 from Midsouth Shooters Supply.¬† The Lyman .358 size die sizes to about the same diameter as most .444 Marlin dies do, about .467″ or less.

NEVER FORCE CASES INTO THE CHAMBER UNLESS YOU JUST LIKE BENDING EXTRACTORS AND HAVING MISFIRES.

THE ADVANCED METHOD DESCRIBED ABOVE WILL BE DONE AS STANDARD. IF YOU DO NOT SPECIFY THAT YOU DO NOT WANT TO FOLLOW THIS PROCEDURE.  YOU MUST SEND YOUR SIZE DIE AND SPECIFY THAT YOU DO NOT WANT TO HAVE TO USE A .444 MARLIN SIZE DIE WITH THE CHAMBER I CUT.

Another option is to purchase small base dies. This lets me cut a close tolerance chamber, and no .444 Marlin size die is required.  However, small base dies are usually priced higher.

Each cartridge is defined as follows:

The standard 7mm-08, .308 Win, or .358 Win chamber is cut .040″ deeper than standard.

Chamber neck is extended for a maximum of 2.215″ overall case length.

Cases for each are formed from full length .444 Marlin brass trimmed to standard .444 Marlin trim length, 2.200.” ( 2.215″ max.)

For Info about each, Click the link below

(No. 2 versions of each are available for the Encore.)

No Expensive Custom Dies Required!

Each uses the corresponding 7mm-08 Rem., .308 Win.,  or .358 Win. dies.

“Advanced” approach also uses a .444 Marlin size die body.

Chamber Drawings and Loading Data for The Bellm Triad:

The data referred to above was developed in a highly controlled regimen, fully tested for pressure and accuracy. It was developed in Thompson/Center factory production barrels rechambered by Mike Bellm. As with all loading data, it is presented for use at your own risk. No liability is assumed by Mike Bellm or Don Shearer for any damages or injuries resulting from the use of this data. This data represents performance at pressure levels deemed safe for use in the Contender. While some promoters of their wildcat cartridges advertise velocities 100 fps or more faster than presented here, they also invite you to stretch your frame. If you choose to exceed the loads presented here, do so with the knowledge that you are on the ragged edge of what the Contender will handle. Also, if you stretch the lower part of the lug on your barrel and it becomes loose on your frame, I will not make any replacement of the barrel to you. You are on your own, and I won’t pay for your mistake.

Even though Thompson/Center does replace stretched frames, it is irresponsible to ask them to pay for your desires to hot-rod your loads.

Stay within the levels listed below, and you will get some of the best accuracy you will ever experience with a Contender along with top long range energy and trajectory performance.

All the best, and good shooting………….. Mike Bellm

Summary of Options for Resizing cases:

(In case you are confused)

Please Choose One of the Following Methods for Resizing Cases for the Bellm Cartridge of Your Choice

With each of the 3 options above, please send your stripped size die body or .444 Marlin stripped size die body if you choose to use one.  Or, your .358 Win Lyman size die body.  Confused?  I want the die that will size the smallest at the web to make sure you can size the case webs down.

This lets me check dimensions and assure a good match of dies and chamber. It eliminates possible problems associated with variations in various size die dimensions.  Please DO NOT send the entire size die or die boxes.  It only complicates packing and shipping.  A stripped size die body is much easier to pack with the barrel, and if there is no lock ring or decap stem installed, it is much less obtrusive and much less likely to do damage to the barrel in transit.

Read also from these links:  The Experiment Every Contender Shooter Should Perform and  Chamber Throats 101.

Please Note: 7mm Bellm, .308 Bellm, and .358 Bellm are reserved primarily for Contenders.¬†¬† For Encores I have “NO. 2″ versions of the 7mm and .308. For .358 I use the .358 JDJ reamer. Standard 7mm-08 Rem., .308 Win, and .358 Win. dies are also used for these rounds, but with their longer case bodies, a .444 Marlin die is needed for all three so as to be able to size the web area. These are relatively new and no data has been prepared for distribution as yet.

The increased case capacity of course means increased velocities over the original chambering, but the main reason for going to the full length .444 Marlin case is to cut out the original factory throat and allow me to cut a minimum diameter, long leade angle throat that IS aligned with the bore.  Thus the No. 2 versions are intended as much or more to correct the barrel for accuracy as they are for increased velocity.

Notes:

Size dies must be long enough inside to accommodate the full length necked down .444 Marlin case.¬† All RCBS dies are long enough inside.¬†¬† Lee and at least some of the Hornady dies are too short inside and won’t work, except for the standard .444 Marlin die which is ok of course.¬† Experience with Lyman dies has been limited, but so far they have worked perfectly.¬† Lyman dies are priced more reasonably, especially the .358 Win. dies, and tend to size smaller than RCBS dies.¬† This makes the Lyman dies preferred for the dimensions I cut chambers to.¬†¬† At this point I am leaning more toward the Lyman dies until such time as I learn otherwise.¬† Bottom line, RCBS and Lyman are my recommendation.¬† Redding is good, but to avoid having to cut a chamber that bulges cases, with Redding you will most likely have to use a .444 Marlin size die to size the case webs down.¬† For 7mm Bellm and .308 Bellm, the Lyman .358 Win dies can be used in lieu of a .444 Marlin size die.

Starting .444’s through a .375 JDJ or .358 Win. size die first helps reduce losses in subsequent stages of necking down. Worst loss I have experienced is about 8-10 cases per hundred. Starting with .375 JDJ or .358 Win. can reduce losses to nearly 0.

Always start with the .308-type size die backed off about one full turn. Trim cases to something under 2.200.” Take the barrel off the frame, and drop a sized case into the chamber. Then……

A Little About Case Forming:

.358 Bellm requires only a set of .358 Win. dies to size and load.  Lyman .358 Win dies are recommended.  These excellent dies are available from www.midsouthshooterssupply.com for under $20, as opposed to over $40 for RCBS and Redding dies.

.308 Bellm can be formed with only the .308 Win. size die, so long as the .444 Marlin brass cases are well rounded at the mouth. Sort out those cases with badly dented mouths which will result in a crease in the neck.

7mm Bellm cases must as a minimum be started in a .308 Win. size die. Even if you have to buy a used set at a gunshow for $15, this is cheaper than buying “form dies.”

4) eliminate the cost and delivery time for custom dies,

5) minimize case forming work and cost of dies to form cases (only 7mm Bellm must use more than just the size die to form cases),

6) eliminate having to fire form cases,

7) provide an ample powder capacity for maximum performance with slower powders, while

8) maintaining a sufficiently high loading density with faster powders and lighter bullets,

9) create a chamber that will not fire high pressure rimless ammo such as 7mm-08 Rem., .308  Win. or .358 Win, and has a greater volume so as to reduce the potential hazards of firing  .307 Win, or .356 Win. ammo in the Contender, AND

10) provide maximum accuracy and performance in a highly “user friendly,” sanely priced¬† package.

a) Typical Bellm chamber based on the .308Win. body easures¬† .467″¬† at¬†the¬† web area, ¬†.457″ at the shoulder for a total taper of just .010.”

b) Contrary to erroneous statements made by magazines as gospel, it is the  minimum body taper  that reduces back thrust, not the shoulder angle as  they  would have you believe.

c) “Improved” cases with 40 degree shoulders nearly always incorporate a¬† minimum body taper, and it is the minimum body taper, not the¬† shoulder¬† angle, that reduces back thrust. The effects of minimum taper¬†can¬† be very easily demonstrated, especially in any straight wall chamber.

Get the benefits of a stronger case, a rimmed case, a minimum body taper chamber, and greatly improved accuracy and performance with minimal case forming.

No fire forming required!

Purposes behind the design are to:

1) cut a chamber long enough to cut out the misaligned, oversize factory chamber throat and permit me to cut a precision throat of the correct diameter for best accuracy aligned with the bore (.444 is about.160″longer than a .30/30, just enough to make a huge difference in accuracy!),

2) utilize a rimmed case that is stronger than the thinner brass for low pressure 7-30 Waters,  .30/30, and .35 Rem. brass used in the factory chambers, thus permitting good extraction and case life at higher pressures and thus higher performance levels,

3) take advantage of the reduced thrust back to the frame provided by the minimum body taper of .308 Win.-type chamber bodies and the strong .444 Marlin brass,

The Bellm Triad Cartridges

Cartridges based on the .308 Win. case body and .444 Marlin brass for the Thompson/Center Contender <br>Unfortunately, only Remington .444 Marlin brass is acceptable for necked down versions based on .444 Marlin, and as of this date, 12-10-2015, Remington .444 Marlin brass is not being produced, nor is there any forecast from Remington as to when it will be produced again.

Maximum Pressures With .444 Marlin Based Wildcat Cartridges, Click Here