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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. 🙂

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.