Contender Barrel

L

lilguy

Guest
I am a long range handgunner, My first project is rechambering a 357 mag Contender barrel to 357 Rem/Max. A .310 additional case length over the Mag.
I have the Midway cataloge. Do I need any other tooling besides the chamber
reamer. Gun work on your level is all new to me. Thanks.
 
You will need a lathe and some indicators to tell you when the barrel is running true plus several other niceties. If this is your first project you picked a doozy and without being offensive I would suggest you start at a lower level. One thing in your favor is that it is a rimmed cartridge so you probably can't get the headspace wrong.
 
It's all in the forcing cone.

Lilguy,
I have considered the same conversion. With a little google searching I found that the 357 maximum with standard chamber seems to be handicapped by a overly large forcing cone. Mike Bellm says the standard forcing cone is from .380 (the outside of the case neck) down to the bore diameter. Too large for a 357 bullet.

I have not dealt with them, but it may pay you to let him do the work. Here's the link.

http://www.bellmtcs.com/store/index.php?cid=120

Regards, Ron
 
Watch out!

In concept you are simply advancing the chamber for the new cartridge length.

But if your current chamber is just a little bigger than your new reamer you may be in for an unpleasant surprise. It would be a lot easier if you wanted a new chamber that was significantly larger so it would "clean up" completely. This one might or might not. But its a straight wall pistol case so a little blending of the old cut and new cut can be done if the difference is not too great. So you'll end up with a gun that goes bang, but may not be a fine example of the gunsmith's art.

I'd make a chamber cast and carefully consider if I had a chance of cutting a new good chamber. If the cast is bigger than your new reamer you may make a mess of the job.
 
henrya said:
. . . . But if your current chamber is just a little bigger than your new reamer you may be in for an unpleasant surprise. It would be a lot easier if you wanted a new chamber that was significantly larger so it would "clean up" completely. This one might or might not. But its a straight wall pistol case so a little blending of the old cut and new cut can be done if the difference is not too great. So you'll end up with a gun that goes bang, but may not be a fine example of the gunsmith's art.
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100%

I had my original .357 Mag barrel rechambered by local gunsmith for .357 Max when it first came out as a factory load (vs 357 SuperMag).

My .357 Mag barrel had a few miles on it when I had this done and there is a thin circumferential groove around the new chamber where the old chamber ended. This leaves a slightly bright mark on the brass where it conforms slightly to this groove, then rubs as it's extracted. Whether this groove is a sign of erosion at the end of the original chamber or a symptom of reamer vs existing chamber diameter I don't know.

The effect essentially seems harmless, but makes it seem like it needs cleaning when you look into the chamber end of the barrel, like shooting .22 shorts in a LR chamber and a ring of fouling remains.

I was also cautioned at the time to keep my "Max" loads reasonable, since the original barrel was an octagon style and the pressure limits for a .357 Max well exceed a .357 mag.
I'd make a chamber cast and carefully consider if I had a chance of cutting a new good chamber. If the cast is bigger than your new reamer you may make a mess of the job.
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If there is not a lot of diameter difference, can a properly sized piloted reamer get far enough into the bore to do it's job?
 
Buy a new barrel

I'd put the money on a new barrel in .357 Max if that's what I wanted to shoot. A nice new barrel with a nice perfect chamber.

When you're trying to do this kind of re-chamber there's a pretty good chance of it not being satisfactory. Its the straight wall pistol case that's causing the problem for you. But it can happen when reaming a .222 to .223 (for instance). You can end up with a "seam" in the neck.

I guess it depends on your standards. If you are happy with a cobbled up chamber its your pick.

You could make it a .35 Remington or a .357 Herrett either of which would clean up the .357 Mag chamber.
 
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