Since your all a fountain of knowledge is there a difference between 357 sig and 9mm

[tayous1]

So looking to reload for my new AR-9 with a 16" barrel I do want to go and get a 10.5-inch barrel for it and yes it is registered lower is another!

Talking with people about the best 9mm bullet I was told by several people I should load 357 sig bullets. They are both .355 as we all know but I was told the 357 sig bullets have a thicker metal for their JHP so they will keep together under the higher velocity for the 357 sig.

I'm not sure as to when I looked up 357 sig bullets pretty much all were for 9mm and said 9mm on them I did see one or two that did say 357 sig!

So want to know anyone knows if there is a difference? I know not a Boolite question but there is no place to ask about this(?)

So if anyone could help me out since 9mm loading for a rifle is a first for me and I want to stay in the 124/125 gr since that's what my mold I have puts out. Or maybe I need to get a 147gr mold? Any advice would help on the 357 sig JHP or what size bullet or Boolite I should use! Thanks!

[cwtebay]

It is not an invalid question. The typical 9mm bullets are designed for 9mm parabellum velocities from a pistol length barrel. The same question is asked when choosing 9mm parabellum for any PCC in regards to powder choices, velocity, and projectiles. There are some very good sources on this forum, as well as Lucky Gunner on YouTube (they explored this a while ago). I ended up choosing some that may be off the reservation from some.

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[nhyrum]

I've got no actual evidence, but, if there's a difference, I'd suspect it would only be in jacket thickness. Kind like the Hornady 452 250/300 grain xtp and xtp mag. But I honestly don't even think that's the case. I use 9mm bullets in my 9x25 Dillon and they hold up fine. 9x25 is basically a 357 sig but based on a 10mm parent case instead of 40. I've shot the 90 grain xtp almost 2000 fps with it.

Use 9mm bullets, but I'd try but not to use plated, but if you did, just keep them under the specified velocity.

As for using cast, as I just realized what forum this was, I'd prefer a gas checked boolit or (dare I say it here...??) Powder coat them

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[rintinglen]

Although there are some 357 SIG Bullets (eg. Speer part no. 4360, Sierra #8125) designed specifically to perform better at the 1400+ FPS level, most manufacturers just sell .355 bullets and call it good for whatever 9 mm cartridge. Usually, a 125 grain 9mm bullet was intended for the 357 SIG, while the 124 grain is for "regular" 9 mm Luger cartridges. However, I am not sure that the difference is sufficient to pose a problem. The slightly thinner bullet jackets may disintegrate or expand more violently, yet I highly doubt that a 150-200 FPS increase in velocity is going to make that much of a difference. Were it I, I would buy whatever 124 or 125 grain bullets that I fancied at the best price I could find and call it good.

[tayous1]

All Boolite are powder coated in my home! Have not seen any negative from shooting them from 750 fps to 2,000 fps.

I agree with both you! I have not seen anything that says that "357 sig bullets" are any better or well suited for higher FPS then 9mm.

I'm sure now some 357 sig loader will correct me! If so it's something new I learned today!

[yovinny]

The 125gr bullets are the standard weight used for the 1920's 38 Super,, and were around eon's before the bottleneck sig 357.