Necking 357sig to 40s&w?

[silicosys4]

Hello,
I recently came into a hundred or so 357 sig cases. I don't have a 357 sig barrel for my p229, and don't have a dedicated 357 sig.
I was reloading some .40s&w, and just for fun after I was done with the batch, I ran 1 357 sig empty through the machine. It sized down and necked up fine and is a few thousandths over the trim to length listed by Lyman's, so I stuck some powder and a bullet into it, and now have a round that looks identical to .40s&w except for the headstamp. I don't have enough brass to think about selling or reloading it, no gun to shoot it from, and unlike my recent purchase of a lot of 9x18 ammo, no real desire to buy a gun or barrel to start shooting it.

Can I just resize it and load it to .40s&w? Or are there factors I'm not realizing? I found data online about the problems with going from .40s&w to 357 sig, but nothing on the reverse.

Many thanks.

 

[rcmodel]

I've never tried it, but it seems stretching the .357 case neck back that far would make for some thin case necks.

I would be cautious of not having sufficient case neck tension to hold a .40 bullet against feeding set-back.

Bullet set-back during feeding can shoot your eye out.

rc

 

[jstein650]

I'm trying to see how I could have done that. Is there an internal sizing button on your decapping pin doing that resizing or is it in flaring for the new bullet? My flaring dies would never expand a full millimeter without some real stress on the handle (and brass). I've only used Lee carbide pistol dies and Dillon dies that drop into the press and the de-priming pins don't have that little button sizer like a bottleneck rifle die.

 

[oneounceload]

The 357 Sig was made from 40 brass in the first place, wasn't it?

 

[Walkalong]

I doubt it would lead to good case life if it worked at all. I bet there are .357 Sig shooters out there who would love to trade you some .40 brass for it.

 

[ReloaderFred]

The 357 Sig case shares the same measurements as far as the base and rim are concerned, but the web is slightly thicker for the higher pressure, and the case is longer than the .40 S&W case.

Seems like a waste of good 357 Sig brass, when .40 brass is so prevalent.........

Hope this helps.

Fred

 

[Blue68f100]

Find someone to swap brass with, then both win.

 

[jstein650]

Of course, the .357 Sig was based on the .40. My question is, we're talking sizing UP. Do most other pistol dies have something to bell the case OUT? None of my pistol or revolver dies do. Other than the powder drop deal which will flare the case out a little. Just curious if, as I stated, there is something different out there in the way of dies that I'm unaware of.

 

[beatledog7]

.40S&W brass is readily available, 357 Sig is far more rare (at least there I shoot). Why would you want to tune rare into common? Couldn't you do better trading or selling/buying?

 

[Certaindeaf]

I think there's a theme here.

 

[david_r]

That maximum brass length is sort of a, well, a maximum. Beyond that length you are creating excessive head space.

 

[silicosys4]

I was wondering myself if my rcbs dies would size it. It is a standard 3 die 40s&w/10mm 3 die set, decapping/sizing die...case mouth flaring die...and seat/crimp die. The decapper/resizing die squeezed the case body down pretty hard, but didn't touch the neck. The rcbs flaring die I had was the one that actually sized the neck.


Anyways, they are on the pay it forward thread, let me know via pm if anybody wants them

 

[jstein650]

OK. Wow. Then that die expanded the neck more than a lot of pistol dies would. If it does, then, as above, just trim and see how it goes, I guess. (I'm thinking you meant 'seat' not 'sear'.)
Can't argue with above - .357 Sig is a lot harder to come by than .40
At any rate, I learned something new.
Cheers!

 

[JimKirk]

Unless you have a very tapered expanding button ... you will collapse most of the shoulders by necking up.... I played with necking some 40 S&W down to 357 SIG ... just to see how they would work .... I tried to open them back to .40 S&W with regular dies and collapsed most of the ones I tried ....

 

[danthearmyman]

I'll swap case for case