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

[Geezer in NH]

Friend has a SIG in 357 sig can he make it from .40 S&W and how?

[Tackleberry41]

No, the already short neck is even shorter when made from 40, he will need to break down and buy proper 357 sig brass.

[willie_pete]

I've done it before; just for grins, it worked for a light load, but yeah, too short.

wp

[DCM]

Can it be done, yes With Care and caveats.
Do I recommend going through all the trouble needed to make sure they are safe No!

In order to make the proper brass it is better to use 10mm as a starting point.
As mentioned above 40S&W will be too short once formed to 357 Sig.
This round is designed to headspace off of the case mouth.
Being too short in the brass department it cannot do that.
So if one wants to use this brass one must make it headspace off of the shoulder instead.
This makes this brass only safe to use in the gun it is headspaced for.
This also makes the area left to grab the boolit considerably shorter, thus leaving less neck tension for the boolit allowing for easier boolit set back which can drive pressure through the roof!
I do load for the 357Sig and tried all this stuff only to drop the whole plan.
So you gotta ask yourselves do ya feel lucky? OK Really lucky?

I recommend the swappin and sellin route instead.

[osteodoc08]

Once fired 357sig brass is fairly cheap. Buy the right stuff for the reasons listed above.

[rodsvet]

The round functions much better head spacing off the shoulder. If you use AA9, there will be no setback in 357 brass if you shoot near max loads. It's a great round, especially in a Sig firearm. I shoot Saeco #924 GC over 12.5 gr. AA9. It moves at about 1400fps and is dead accurate in my Sig229. Rod

[Tackleberry41]

I bought a bag of 500 once fired 357 sig a while back, its not worth the effort to go converting say 10mm to 357, since the brass is pretty much the same price. Oddly 100 once fired 10mm is more than 100 new ones.

It would be nice if 40 could be converted over, I ran a couple thru the die, and there isnt much neck to grip the bullet. If you were using bullets with a cannalure you could probably roll crimp them enough to prevent set back. But not much in way of 9mm bullets with a cannalure or if they did probably wouldn't be where you needed it, you would have to buy the machine to cut your own, the price of which would buy alot of the proper brass.

[Geezer in NH]

Thanks guys I will let him know to get 357 sig brass

[too many things]

he also has to watch the type bullets as many will not work in the sig case as the neck is too short. AND NO GC type will work
blew a crony up with GCs

[Tackleberry41]

I use the xtp in mine, they need to be a trunicated cone type, anything round usually wont crimp.

[rodsvet]

I beg to differ that GC's won't work. I"ve fired thousands through my 229 using Saeco mold #924 and Hornady checks. Your mileage may vary. Rod

[khmer6]

357sig can be finicky. Bullet type matters. I like the saeco 122gr tc? Shoot out of a sig226 dak it's a tack driver with some unique. Converting some 40sw makes it a bit short. Sig brass is plenty. If he is in need of some I May have a surplus stash

[Spawn-Inc]

well that's interesting, i thought it was common place to use 40's for it. i guess the biggest thing is not enough neck tension allowing for easier setback.

[khmer6]

well that's interesting, i thought it was common place to use 40's for it. i guess the biggest thing is not enough neck tension allowing for easier setback.

It is confusing since the Sig is a necked down 40sw as they say. One would naturally assume a necked down 40sw case would make cheap Sig brass. I thought this too when I first bought mine. Turns out my experience mimic many others as it was too short and at the time brass so was cheap and plentiful there was no sense in converting. Plus ammo was only 20cents a round delivered to my door

[Tackleberry41]

I would imagine then when coming off the assembly line untrimmed 40S&W probably does easily make 357 sig, but trimmed to 40 length, its not long enough anymore. Now if you had a pile of 10mm you werent using then you could convert.

[xacex]

I use 40 S&W brass for pump and dump plinking loads. The 357 shooters in my club use it for competitions where they won't be picking up their brass. 357 sig is supposed to headspace off of the neck not the case mouth. With the shorter neck I use a slight crimp to make certain I do not get bullet set back. DO not use full power 357 sig loads, and do not re-use the brass as an extra level of precaution.

[dkf]

The .40 brass I ran through my .357sig sizer ends up being around .020" below SAAMI minimum brass length for .357sig brass. Back in the day when .357sig brass was hard to find turning .40 brass into .357sig was very common but not ideal. You can buy once fired .357sig brass for $40-$50 per 1k these days so making due with short brass made from .40 is not really needed anymore.

[xacex]

The .40 brass I ran through my .357sig sizer ends up being around .020" below SAAMI minimum brass length for .357sig brass. Back in the day when .357sig brass was hard to find turning .40 brass into .357sig was very common but not ideal. You can buy once fired .357sig brass for $40-$50 per 1k these days so making due with short brass made from .40 is not really needed anymore.
I agree it is not needed however if you have a bunch of .40 brass, and won't own a .40 if someone gave one to you it certainly is a way to get rid of it. At the two clubs I am a member of I pick up quite a bit of .40, and hardly any .357 sig. So, I get some use out of it before it goes in the brass recycling bucket. As long as you are aware of the shortcomings there is no problem using it. Like I said, no full power loads, light crimp, and toss after one firing and you will be ok. When the .357sig first came out there was no brass available for it, and this was a common practice. Just be aware that the neck is short, and the pressure must be kept 5000 psi lower than 357 sig loads. 35,000 psi for .40 vs 40,000 psi for 357 sig.

[TheDoctor]

Market it as your own round. The 357 GAP! Solution to a non-existent problem.

[xacex]

Market it as your own round. The 357 GAP! Solution to a non-existent problem.
That funny!

[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]

234594
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.