Fire-forming 357 SIG Brass to 40 S&W?

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kcofohio

kcofohio

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Over the years that I have picking up brass, I rarely find nickel plated 40 S&W cases. I may have about 60 pieces total. I'd like to have about 100 more of them. But I have a coffee can full of 357 SIG nickel plated cases.
I know fire-forming is generally for rifle cartridges. But I'd like to reallocate some SIGs to 40.
My plan is to load up 125 gr. with a load I know is good. Then fire them out a 40 S&W barrel. Then they will need trimmed.
I tried working with a Lee universal expander, 40/10 sizer, and Lee's powder through die. But the case has an hour glass shape.

Has anyone here tried this. I searched the web, but came up with many about converting 40 S&W to 357 SIG.
 
I don't think you will get enough pressure to blow the case out. As soon as the bullet leaves the case the gases will blow by the bullet.
Make sure each bullet leaves the barrel before sending another one.
 
Highland Lofts said:
I picked up a bunch of 40cal and have some nickel plated if you need them.
I wouldn't waste the time & energy to transform the 357 to 40cal.
If you need the brass shoot me a pm. I have some 9mm & 45acp as well.
Click to expand...
Thank you for the offer! It isn't anything pressing. Just a cold morning had me thinking. :)
 
You won't get enough pressure to blow the brass out.

Not really worth the effort, personally. Sell the Sig brass, buy 40 brass.

If I HAD to do it, I'd try loading some fast pistol powder, then stuff the case with cotton. Let the cotton "slug" blow out the case to 40 caliber. How much? No idea.
 
I went to gun range when I came back to New York to take my grandson small game hunting in October and picked up a bunch ofpistol brass; probably around twenty pounds of it.
 
I wet tumbled half of the 40 caliber I picked up.i will putthe brass on my drying racks tonight and wet tumble the other half of it tonight and will separate the nickel brass from the regular brass.

Pm me your shipping info and I will send you some.
 
I have nickel .40’s, LE used to use the range I belonged to. Let me know? @JimKirk, (Star Trek fan?), maybe we can do a three way trade? :)
 
kcofohio said:
Has anyone here tried this. I searched the web, but came up with many about converting 40 S&W to 357 SIG.
Click to expand...

I accidently fire formed a 357sig case in a 40s&w barrel. What I remember is that the accuracy of the .355" projectile was terrible. I normally keep these "oops" cases. Let me see if I still have it, then I'll post a picture.
 
The ONLY pistol case failure I have had, involved nickel plated 40. Why? I could not see the "bulge" in the case from previously being fired out of a chamber that does not support the case. head completely.

I would waste my time on converting 357 cases. If you want some nickel plated 40....somebody above offered. I have a full coffee can as well.
 
I just watched a video on You Tube where that was just done, sort of. They only did one round, showing it was possible to load and fire a .357 SIG from a 10mm barrel (and pistol). The round came out ready to load. It was only one time, and in a 10mm chamber. The extra length of the chamber might make a difference. Also, this .357 SIG was a factory full load.
I rather doubt the pressure would be high enough to damage the pistol. I suggest a 'fast' powder would work better than a 'slow'. Seems to me to be expensive and the long way around, but if sufficiently bored...
 
Used range brass is easy to come by and cheap or free, why bother.
Plus you have the proper head stamp.
When it comes to reloading I never cheap out.
Do it right or don't do it for me.
I have over $4,000 invested in reloading so buying the right stuff is cheap and you can expect good results.
Not downing any one just my personal view.

I have a hundred 40 caliber nickel plated cases dry and will have a couple hundred more here shortly and will pay postage.
 
Would the 9mm round go plunkity plunk from wall to wall on its way out of your .40 S&W barrel in the process? :rofl:
 
Perhaps with a properly - profiled mandrel, you can...

...but you'd probably weaken or tear the case lips in the process.
 
Thanks for all the offers and input! :thumbup:

The curious part of me decided to make an expander. A 1/2" shoulder bolt turned down with a polished 15 degree taper. I used the Lee universal expander for a start. Too much does crack the cases. :uhoh:

Curiosity satisfied. After ruining 13 cases, I have 52 good conversions.
20211217_213517.jpg
20211217_213745.jpg

The cracked cases were from the universal expander going to deep. Once set properly, it was good. Case mouths were lubes using RCBS Case Lube-2 applied with a q-tip.
 
A couple of years ago there was a thug in the City of Baton Rouge, LA. That was shooting 357 Sig out of a 40 S&W. After one Homicide and two attempt murders, the detectives asked my opinion. They thought the thug was using a pistol chambered in 357 Sig.
I took a good look at the cartridge cases from all the shootings and told them that the shooter was shooting 357 Sig ammo in a S&W M&P 40.
They asked how I knew what gun the shooter was using. I told them (at the time) the M&P had a unique breach face and firing pin markings.
The neck of the cases had a small ring at the mouth where the chamber ended.
A month or two later they arrested the guy and he had a S&W M&P 40 that was loaded with 357 Sig ammo. I test fired the gun with 40 and 357 Sig ammo.
@kcofohio , I have a bunch of 40 S&W brass, and a good bit of it is nickel. I would be more then happy to send you a bunch if you want it. No charge, not even shipping. Call it a Christmas gift.
 
I am looking for .357 sig for a future handgun. If you want to trade, I'll look at my 40cal stash and trade you. I have a lot of 40 brass and most like have nickel brass too.
 
I should look at my 40 S&W stash I may have some nickel cases I could send as well. I don’t shoot 40 much anymore and for reloading in that caliber I don’t care nickel or brass.
 
GunnyUSMC said:
A couple of years ago there was a thug in the City of Baton Rouge, LA. That was shooting 357 Sig out of a 40 S&W. After one Homicide and two attempt murders, the detectives asked my opinion. They thought the thug was using a pistol chambered in 357 Sig.
I took a good look at the cartridge cases from all the shootings and told them that the shooter was shooting 357 Sig ammo in a S&W M&P 40.
They asked how I knew what gun the shooter was using. I told them (at the time) the M&P had a unique breach face and firing pin markings.
The neck of the cases had a small ring at the mouth where the chamber ended.
A month or two later they arrested the guy and he had a S&W M&P 40 that was loaded with 357 Sig ammo. I test fired the gun with 40 and 357 Sig ammo.
@kcofohio , I have a bunch of 40 S&W brass, and a good bit of it is nickel. I would be more then happy to send you a bunch if you want it. No charge, not even shipping. Call it a Christmas gift.
Click to expand...
I may accept your generous offer. And, since it's a Christmas gift, if you don't mind, I would like to gift to other members some 357 SIG as a forward from Gunny.
 
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