Producing 357 Sig from 40 S&W
- Thread starter horseman2
- Start date
Yes, I have made several thousand from 40 S&W cases.
Adjust the sizer die so it does not quite hit the shell holder. This will give a better cases should location.
Size a dozen and them take your barrel out and see how they chamber.
If they look reasonable, make 50 or 100 and shoot them.
If you get misfires it probably means you have to back the sizer out a half turn to move the shoulder out a bit.
I have had zero problems.
I load the 124 gr plated bullet with the flat nose and the 130 gr cast round nose flat point bullet. The latter is very very accurate in my Glock.
Adjust the sizer die so it does not quite hit the shell holder. This will give a better cases should location.
Size a dozen and them take your barrel out and see how they chamber.
If they look reasonable, make 50 or 100 and shoot them.
If you get misfires it probably means you have to back the sizer out a half turn to move the shoulder out a bit.
I have had zero problems.
I load the 124 gr plated bullet with the flat nose and the 130 gr cast round nose flat point bullet. The latter is very very accurate in my Glock.
The 357 SIG is a bottleneck case, with a shoulder.
The factory made case headspaces on the case mouth, not the shoulder. The shoulder is formed a little too far back to touch the chamber.
If you make cases from 40S&W, the resulting case is a bit short, which would affect the case headspace. Hence the advice by some that it does not work.
But, the short cases seem to work just fine.
In my posting above, I noted that if you don't quite screw the sizer down all the way, the shoulder will be formed a bit closer to the case mouth and the case can then headspace off the shoulder instead of the case mouth. Correct headspace is easier on the brass and puts the primer in the correct place for better ignition.
The factory made case headspaces on the case mouth, not the shoulder. The shoulder is formed a little too far back to touch the chamber.
If you make cases from 40S&W, the resulting case is a bit short, which would affect the case headspace. Hence the advice by some that it does not work.
But, the short cases seem to work just fine.
In my posting above, I noted that if you don't quite screw the sizer down all the way, the shoulder will be formed a bit closer to the case mouth and the case can then headspace off the shoulder instead of the case mouth. Correct headspace is easier on the brass and puts the primer in the correct place for better ignition.
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Easily done. and with a DMT Whetstone, you can shorten your die and it will work perfectly. I shoot SIG regularly. Yes the case is slightly shorter, but the BDX bullets grip quite well. Berrys, not so much.
Why shorten the die? That would push the shoulder back.
I size with the die not bottomed so that the shoulder moves forward a bit so the case can headspace on something.
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Because I cut my own chamber
PTG Piloted reamer, knew i was using .40 brass, and sized everything accordingly. Added to the fact the Dillon Die is not quite perfect spec, it was a slightly better solution. I suppose I could simply have made my own dies from a blank 
Because I cut my own chamber
Wouldn't it make sense to include this info in the previous post? Otherwise you're giving advise about shortening dies that isn't applicable to most...
Because I cut my own chamber
So you more or less made a 9x40...
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Not at all. a 9x40 has a squared shoulder.
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Honestly it never crossed my mind. When making SIG rounds from 40 brass it's best to plunk test them in the barrel, and cover them in soot to see what you have. My chamber has a lot less slop than most. And my Ammo fires and hits accurately in other 357SIG guns.
Although it does headspace on the rim, the extractor still holds the breechface, no doubt there is variance in some guns more than others.
.357sig headspace spf the case neck.
9x40 has a squarer shoulder and head spaces off of it.
Extremely similar yet incompatible.
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Correct.
That being said, I have seen 9x40 work in a 357SIG, it DOES fireform to the chamber (seen this happen, not in my gun)
But 357SIG is NOT back compatible with 9x40. Gun will fail to go into battery.
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What would you like to know. there is no SAAMI spec for 9x40. so you will not find that detail. Back in the day, when bullet setback was an issue for 357SIG that was made before people used ROLL CRIMP on the projectile, (this happens when you use shorter brass to make the SIG brass. the lack of a roll crimp could cause dangerous overpressure if bullet setback happened when the round's nose hit the feedramp made a shorter COAL and then chamberes. Pull the trigger, kboom!)
So, Gunnar and a few other Smiths took 357SIG Reamers and rebated the rim flutes to 90 degrees off of the 9mm round at 27 degree angle. This shortened the round further by pulling the neck rearwards and leaving more meat on the throat so the bullet would have more tension on the neck.
100% ballistically the same, but dimensions on the neck and brass length vary.
Of course once folks started using more jacketed ammo, and roll crimping their ammo, the problem pretty much went away.
Nothing wrong with SIG or 9x40
