Loading .357 mag .355 vs .357

[ohioshooter]

Has anyone used 124 grain .355 bullets over the .357 125 grain bullets? I have some left over from loading .357 Sig and was either going to trade them or just see if I use them for the .357 Magnum. I would be using them in a Coonan .357 and not a wheel gun.

 

[rcmodel]

Not a good idea.

Especially in an auto-loader like your Coonan.

Case neck tension will be very poor unless you go through some gyrations to neck size them in a 9mm die & use a 9mm expander or something.

The risk is bullet set-back during feeding resulting in a Kaboom.

Besides that, accuracy will not be anything to write home about with a .002" undersize bullet.

rc

 

[ohioshooter]

looks like I may have a few hundred .355 bullets up for trade...lol

 

[tyeo098]

Are they plated or jacketed?

I've used in the past a plated 124gr .355's in 38spl and 357, since the plating is thin and the lead is soft, I roll crimped it enough to make my own crimp grove.

But if rcmodel says its a no-no I wouldn't do it. His experience, and therefore opinion carries much more weight than mine

 

[rcmodel]

It's safe to do it in a revolver.

I just don't think it's safe in an auto-pistol like the OP's, unless special case sizing steps are taken to prevent bullet set-back during feeding.

rc

 

[ohioshooter]

If I can recall they are Hornady XTPs

 

[gamestalker]

And even if they were loaded for a revolver, and depending on what type of load it is, you would likely have bullets jumping out of the case mouths with anything more than a light target load.

GS

 

[WestKentucky]

I do load .355 over 3 gr 231 in 38spl cases, but my bore is a bit small as it slugs at .355. Accurate and easy to shoot but I am downloading this one intentionally. And a standard roll crimp does fine.

 

[tightgroup tiger]

Accuracy will suffer bigtime if you barrel is true .357. I bought a box of Hornady XTPs in 38 cal and loaded for my .357mag. My normal groups I shoot every Sunday at 25yd turned to crap with some not even hitting an 11x17 target at all.
When I got home very confused, I asked here about my loads but then later discovered that my 38 caliber bullets mic'ed at .355 and had a canullure.

Use your .355s for trading stock but don't waste them trying to load accurate ammunition with them. It ain't gonna happen.

 

[NWcityguy2]

There are lots of 9mm guns with barrels .357 or larger and people shoot .355 bullets through them without ever seeing a problem. Unless you slug a barrel you truly don't know what the bore size is, so saying .355 bullets won't work in a barrel that is supposed to be .357 is just speculation.

As for neck tension, I doubt it would be a problem with a strong taper crimp but you are the one who has to experiment with that.

 

[zxcvbob]

Try loading a couple just sizing the brass and not expanding it. If the neck tension is okay, you *might* be good to go. Autoloader doesn't give me warm fuzzies... but with a rimmed cartridge maybe that doesn't matter so much?

Crimp them hard enough for the case mouth to bite into the jacket a little; maybe with a 9mm die.

The only thing you really have to watch out for is bullet setback. Accuracy may or may not be terrible w/ the undersized bullets.

 

[tyeo098]

Load them one at a time.

Problem solved.