357 Sig Bullets

[Olympus]

This may be a dumb question, but my father in law asked me and I had no idea so I told him I would ask around and try to find out. He has a Sig P229 in 357 Sig and says he has several thousand 125gr JHP bullets that I he bought to reload in his 357 Mag revolvers. He wanted to know if he could use those same bullets to reload in the 357 Sig. I honestly don't know if that's possible or not. Can anyone help?

 

[Hartkopf]

I’m pretty sure they will be .001 to .002 too big. The 357Sig is basically a 9mm bullet diameter. There might be finer details that others can elaborate.

 

[bangswitch]

Like Hartkopf said, the 357 Sig uses 9mm bullets, 0.355" diameter. When looking at the data in the 10th edition Hornady Handbook of Cartridge Reloading there are no common bullets between the .38Spl/ .357 Magnum and the 9mm/357 Sig load data.

I find it rather curious, though, the case diameter of a 9mm is 0.380, where the case mouth diameter of the 357 Sig is 0.381 (O.D.) The .38Spl/.357 Magnum case diameter is 0.379 (O.D.), a smaller diameter, but takes the larger diameter bullet. My guess is the larger .357 bullet in the 9mm or 357 Sig case would expand the case mouth enough that there would be chambering problems, since the auto cases headspace on the forward edge of the case, and the larger bullet may have clearance issues in the chamber, or expand the case enough that it is too tight in the chamber.

 

[Walkalong]

It uses "9MM" bullets, but needs bullets with a long bearing surface. Some 9MM bullets don't work well.

I have used some soft plated .38/.357 .357 bullets in 9MM, but don't load .357 Sig, although I think I would stick to .355/.356 for it.

 

[Jimmy Sisco]

The 357 sig can use the .357 bullets if they will chamber. Start at beginning powder charge and work up. they will generate more pressure because they will be swagged down by the bore.

 

[fxvr5]

The 357 sig can use the .357 bullets if they will chamber. Start at beginning powder charge and work up. they will generate more pressure because they will be swagged down by the bore.

How much more pressure will they generate?

 

[JimKirk]

The RMR 124 grain MPR is great in the 357 SIG....

 

[Dudedog]

If he has a lot and really wants to use them and they don't fit you could resize them.
https://leeprecision.com/new-lube-size-kit-.356.html
That would get them a hair smaller.
(or maybe trade them)

If they won't fit , I could resize a small # for you to try, but by the time we paid shipping back and forth you could get the die shipped free from Amazon and not have spent much more $.
PM me if you would like me to try to size some for you.

 

[Jimmy Sisco]

How much more pressure will they generate?

I do not have pressure equipment. But I have used the hornady 140 xtp's up to mid level charge weights of H Longshot with no problem