|
|
SAAMI .357 Remington Maximum chamber. |
| Here is a graphic example of the exact same forcing cone arrangement from a factory .357 MAGNUM chamber. | With the chamber cast, .357 MAGNUM case, and bullet laid side by side, you get a better picture of what is going on inside the chamber. (photo courtesy D.W. Murphy)
|
The only difference between a factory .357 Magnum and a factory .357 Rem. Maximum chamber is the 1.610" length of that portion roughly .380" in diameter for the longer .357 Rem. Max. case.
You can see the shape of the cone compared to the shape of the bullet shank and see that while the nose of the bullet may get centered at with the bore at its nose, the base of the bullet is sitting in a much, much bigger hole that cannot align it with the bore. |
| | | Close up of the .357 Mag. chamber cast. (photo courtesy of D.W. Murphy) |
|
| The spot where the bullet is sitting is the point where it hits the rifling.
As you can see, with this long forcing cone in the stock .357 Magnum factory chamber, the bullet is completely free of the case by the distance shown between bullet and case above before it hits the rifling. Between the long jump and no alignment of the base of the bullet, a chamber like this can hardly be expected to give good accuracy. Again, you have the same long forcing cone arrangement in factory .357 MAXIMUM chambers as well.
Rechambering to the longer .357 Max. case cuts out all but about .1" of the long Mag. forcing cone.
Quoting Mr. Murphy, "I dropped the bullet into the barrel and used the depth rod on my calipers to get a reading of 1.4" from the back end of the barrel to the bullet. I did my best to align the case, bullet, and chamber cast as accurately as possible to show how much room there is for improvement. I should still have at least 0.20" left before the rifling starts. the cannelure of the bullet is about 0.10" to the right of where the case will stop."
|
| What you are looking at in the above drawing and photos is what you DON'T want.
This forcing cone arrangement above is what you get in factory .357 Mag, .357 Rem. Maximum, .44 Magnum and other similar straight wall chambers. However, this same cone is also cut in .22 Hornet and .22 rimfire Mag. chambers as well. On the other hand, some factory chambers such as .30/30, .375 Win., and .45/70 have NO throat in them. |
| Older Vintage .357 Magnum chamber for comparison to the current long forcing cone design. | | Top, cast of a current .357 Magnum TC factory chamber long forcing cone design. Below it, an '80s vintage .357 Magnum TC factory chamber cast with a much shorter forcing cone design. Bottom, .357 Magnum case. (Courtesy, D.W. Murphy) |
Second from the top is a chamber cast of an older vintage of .357 Magnum chamber with a short cone, as opposed to the current long style that is about .4" long. Note how much farther forward the rifling start in the top cast.
This one is still a cone, but it is quite short in comparison and a much better choice either to shoot as is as a .357 Magnum or to rechamber to .357 Maximum, which will cut out all of the factory throat.
Earlier vintages of .357 Magnum chambers have true throats where the rifling only are cut away, leaving a short cylindrical area in front of the case mouth as opposed to the cone present in the bottom cast above. Once again is a .357 Magnum case which demonstrates where the case mouth ends and where the riflings start.
Bear in mind that a number of companies have supplied reamers to TC over the years, and that there are a number of variations that are all construed by the reamer manufacturers to be "SAAMI Standard." There are apparently choices that are acceptable, but some of the designs TC has adopted over the years exhibit a gross disregard for the accuracy you are presumably expecting and paying for. |
| | (Chamber Throat Misalignment Click on this link also for a cast of a misaligned chamber throat.) |
| Below is the .357 Remington Maximum chamber WITH a true throat, what you DO want.
|
| |
| The chamber I cut for .357 Rem. Maximum has a throat in it, NOT the forcing cone you see in red in the top diagram above.
The riflings only are cut away, leaving a true throat, one that is cylindrical and does support the shank of the bullet.
When starting from a fresh barrel, the cylindrical throat starts immediately in front of the chamber neck. But when rechambering a factory .357 Magnum barrel to .357 Remington Maximum, approximately .1" of the smaller end of the forcing cone shown in red above will remain. The .381" diameter of the Magnum chamber body is extended forward into the cone area, cutting it away, all but for about the last .1" of the cone.
Forward of the very short section of cone remaining will be a true cylindrical throat.
For barrels I rechamber to .357 Rem. Max., seat the bullets out as far as practical or to the limits of the throat length.
Where book maximums for 160 gr. bullets with 4227 for example are about 22 gr., I am test firing routinely with 25 gr. and have no excess pressure signs at all.... no primer cratering even.
However, I should note that WW-296 is probably one of the very best powders in the Max.
With the .357 Maximum, you can load it to essentially the same pressures as you would a .223 Rem. in both Contender/G2 barrels and Encore barrels since the two rounds are within just a few thousandths inch of being the same diameter.
The .357 Maximum comes very close to .35 Remington in performance.... a long time, proven meat getter out to about 150 to 200 yards in the hands of a good shot who knows the distance and his barrel's trajectory.
.357 Remington Maximum is one of the very best choices for 10 and 12" Contender barrels. When custom chambered correctly with a true throat, it is extremely accurate.
With the broad range of .357-.358" bullets available, excellent powders in the correct burning rate range, inexpensive brass, and the readily available .357 Magnum dies used to load the Max. as well, it is a "natural" for any Contender/G2 barrel collection.
The new untapered TC factory 12" barrels with the two forend screw attachment for more substantial forends than on the 10" "bull" barrels make it better suited for hunting where field conditions vary a lot. But either length of barrel works great.
As a plus, the crowns on the factory 12" barrels I have examined so far have been quite cleanly cut, clearly showing the outline of each land and groove, and should not require any recrowning work to make the shoot well.
If you are deer hunting in a state that requires straight wall handgun cartridges, don't trip over the .357 Maximum!
For information about rechambering your .357 Magnum barrel to .357 Remington Maximum, please call Mike Bellm at (541) 659-4425.
Send barrels with NO sights or scope base attached and include $95 payment to:
Mike Bellm
3388-B Merlin Rd., PMB 402
Grants Pass, OR 97526
cell #: (541) 659-4425
email and Pay Pal account payment address: mike@bellmtcs.com
|
| More Chamber Casts
along with more explanation of what a throat is supposed to be compared to what you get in factory chambers and from anyone cutting chambers with SAAMI spec. reamers...... exactly what you DO NOT want if accuracy means anything to you at all! |
| | |
|
