.357 SIG be made from .40 S&W?

[UBER7MM]

You might be able to make 357 Sig from 10mm brass. However, 10mm uses a large pistol primer.

[Tackleberry41]

You can use 10mm, but its not any cheaper than the proper brass. Unless someone had a pile of 10mm to use for this. I have never found more than a handful in the buckets of range brass a friend gave me working at a range.

[N1YDP]

what if you grind the shellholder down to get more of a neck?

[Lagamor]

That might work. Shave off 0.025"-0.030".
The grind will have to be flat and perpendicular of course, but it might work.

[Tackleberry41]

Unfortunately if you shave the shell holder, you will be moving the shoulder back to. Its claimed 357 SIG head spaces off the neck, when in reality its the shoulder like every other bottle neck out there. Will short brass, as in the shoulder work, maybe, some guns will hold it with the extractor, some won't. When I size 357 SIG for my gun, the die doesn't even touch the shell holder to begin with, set up for my gun, so shaving it would do little good.

357 SIG brass can be a pain. Some companies are using undersized flash holes, which complicates things. I bought a big bag of Speer and all of it is undersized, even found one so small it blew the primer back. I have some S&B brass its the proper size, but some new remington ammo I bought has undersized flash holes to.

[dkf]

I have a lot of Speer brass and all the flash holes are tight. I use the Lee decapper on them so I don't have issues. The newer Lee decapping pins that have the end turned down don't fit the flash holes in the Speer brass, but the older pins with the pressed in dowel pin fit. FC brass has a decent sized flash hole, don't know why others can't follow suit.

[Tackleberry41]

I mangled several decapping rods fighting w the Speer brass. I even modded one so it wouldn't hang up, then I could drill them out easier. But an overly small hole bent that one, so I drill them before hand, careful not to go thru the primer, then knock em out. What brass I have is all fixed. Whatever loaded ammo I buy in the future, if any will try to stick with brands I don't have to deal with the flash holes. Im sure the ammo companies could spout some garbage as to why they went with the undersized holes, a solution to a problem others have not seemed to have.

[Geezer in NH]

My buddy solved his brass problem! He took the gun on a ride to SIG, they put a new .40 S&W barrel in it now it works with all the State Police brass he has from when he was a training officer.

[Sig556r]

Someone here suggested converting PMC .40SW brass to .357Sig so while waiting for my 1X brass, I converted some & loaded 12g AA9 behind Lee358-125RF seated up to crimp groove with LFCD. They're a little hot maybe seated too deep or crimped a tad tight. I'll back off a grain or 2 next time. The AA2 load behind Lee356-120TC has lesser recoil.
So now, if I ever lose all my sig brass, got a pile of 40s to work with.
BTW LFCD worked better in .40 converts than factory .357 brass.