Forming .40 S&W brass to .357 sig?

[Jenrick]

Just on a whim the other night I chucked a .40 S&W case into my .357 sig die, and it seems to have work just fine to resize though just a tad short. Considering the round headspaces on the shoulder this should only present an issue neck tension.

The reason I'm considering it, is that I have access to all the .40 S&W brass I want for free. .357 sig brass, not so much. For practice I'm perfectly fine shooting light loaded 9mm power level rounds rather then normal power .357 sig rounds. The bullets cost the same regardless of how much powder I put behind them, so no reason to drive them hard just for the heck of it. I'll use actual .357 sig brass for full power rounds.

I know brass isn't the expensive part of the equation when reloading, but if I can cut that cost out by and large I'm curious if there's a reason not to do so.

-Jenrick

 

[rcmodel]

Yes.

The .357 SIG case is neck tension challenged at best.

It needs all the case neck length you can get.

One bullet set-back during feeding, even with light loads, could cost you more then you can save.

Rc

 

[BluewaterLa]

Most manuals and literature I've read about the 357 sig highly warns of NOT using other brass due to safety reasons no matter how possible or tempting it may be.

 

[WestKentucky]

If your going to do it, crimp the piss out of it. I would take a small sample of factory loads and load them in a single stage, then use a spring scale to measure force needed to cram bullet further into the case. I would then resize plenty of 40sw and load dummies in sets of 3 and measuring force of push-in retry it until you can recreate consistently that same force or slightly greater with your crimp setup. You will use your inertia puller a bunch so have it handy.

Another help would be (if even possible) to load bullets with cannellure and crimp in the cannellure which eliminates the setback issue.

I'm not familiar with the 357 sig loading info so others may chime in pointing out my flawed rationale. I have however loaded .355 9mm lead into 38spl and used this process to overcome the total lack of neck tension...it's now one of my favorite loads.

 

[Bovice]

Do not do this. Once upon a time I was reloading 357 SIG with 357 SIG brass. Even then, it was a major pain to get the dies set up to stop from making telescopic rounds. It would be even worse with resized .40.

A max (but safe) load of AA#9 was what I ended up needing to use. It fills the case all the way and helps hold the bullet up.

Your other hurdle is going to be bullet choice. You need flat nosed 9mm projectiles or 9mm JHPs. Most flat nose 9mm bullets are plated. They do not like the 1350 FPS that the 357 makes. Ask my chronograph how it feels about tumbling bullets.

I ended up using 124 grain Nosler JHPs. Kinda takes the economical part of reloading out of the equation.

 

[Jenrick]

The general consensus says don't mess with it apparently, I shall bow to the THR reloading brain trust.

Bovice - Berry's makes a very nice plated .357 sig bullet that you can drive hard if you choose. I'm planning loading at 9mm velocities, so even their lighter plating ought to be fine.

-Jenrick

 

[TfflHndn]

Bovice: Take a look at Montana Gold's .357 sig bullets. They are jacketed flat or hollow points rather than plated and hold up well. At $.15-16 apiece they are not exorbitantly expensive. I got the JHP and they work very well in my P229.

 

[Otto]

You can get 1000 357sig cases shipped to your door for $45....why bother with reforming brass which may cause a safety issue?