1911 10mm conversion to 357 Sig

G

gmarr

New member
Ok, I like them both, and have both. So that got me thinking about converting my 10mm 1911 to 357 Sig. From what I've read it's pretty easy. Barrel and recoil spring. Anyone done this or know what else is needed?
 
Is there a difference in the lips or follower? Asking for a friend.

The HK MP-5 10mm mags can be loaded w/40 S&W for their 40 Cal SMG. If .357 Sig is just a necked down 40, it might work.... but what do I know? I've never saw a .357 mag for the 1911.
 
There are a few custom 3 barrel rigs I've seen on the gun rags from places that do custom 1911s. I think you could even make a 4 barrel set if you like 38 super too with barrels for 40, 10, 38super and 357 Sig! The difference in rim diameter between 38 super and 10mm based cases is small. I think you can find 40 S&W magazines that would probably have the spacer like the 9mm magazines and use those for 357 Sig. I like the ballistics of the Sig round but being a bottle neck case with scarce free brass and needing to lube cases for reloading I prefer the 38 super loaded hot. You can shoot 9s with a 38 super magazine but they have a lot of space to move back and forth that will cause a malfunction. The 357 Sig is also picky about bullets where any 9mm bullet will work in the Super because of the straight case. While the 357 Sig would certainly be a cool 1911 Conversion for your 10mm, also consider a traditional 38 Super instead.
 
Book say .38 Super rim diameter is .406"
10mm rim diameter is .425"

No, that's not a large amount, but it is enough that it can effect the function of the parts and possibly the geometry the system needs for reliable function.

Remember that not only does the extractor need to grab, but the ejector needs to be in the right spot, relative to the case, or you ejection may be altered.
 
I'm not sure how many thousandths the hook is on a 1911 but I know that Hornady calls for the same shell holder for reloading 38 super and 10mm/40. About the only thing that might be needed is an extractor adjustment or different extractor to make the change over. I've converted a 38 super 1911 to 9mm and it just needed a bit more extractor tension to run correctly so don't get upset about two hundredths difference in the rim diameter.
 
The .357 Sig is based on the .38 Super? Well darn if I'm didn't lurn me something new today. When it was released I was thinking Sig necked down the .40 but .38 Super would be a better cartrigde (more support).
 
WOA Gary, don't misread my comments. 357 Sig is based on the 40/10mm case head which is rimless. But the almost 100 year older 38 Auto/Super case is semi rimmed. The difference in rim size is so close you could do a barrel and magazine swap on a 10mm 1911 and turn it into a 38 Super instead of 357 Sig. With Hot loadings like Corbon there is not that much difference in practical terms between 38 Super and 357Sig.
 
rc - you just invented a new cartridge then! Off to the Patent Office just for bragging rights.

BTW, was speaking with Richard Davis of Second Chance (vest) and he told me that it wasn't worth the stress to protect patents.
 
Gary, the topic is caliber swaps and the 1911. There are basically two breech face cuts for 1911s I would characterize as the 38 super cut and the 45 cut. Some people would argue there are really 3 or 4 different breech face cuts including 9mm, 38 super, 10mm and 45 but I would argue it's more about extractor adjustments than breech cuts when case heads are close in size. If you have a 45 breech face slide and want to push a 40 bullet out the muzzle with a barrel swap you go with the 400 Corbin cartridge based on the 45 ACP case.
https://en.wikipedia.org/wiki/.400_Cor-Bon
If you have a 10mm head cut on your slide like the OP you have a few more options on Caliber swaps. One of them is 40S&W, another 357 Sig without anything but a barrel swap. I am suggesting that the 38 Super rim is so close to the 10mm case head that a 38 super barrel and magazine would probably convert a pistol originally in 10mm to fire .355 aka 9mm bullets just like the 357 sig shoots. The benefit of the 38 super case over the sig is straight walled cases that reload a lot easier and are not picky about bullets. The 357 Sig is know to be harder to reload because it needs truncated shaped bullets rather than traditional 9mm luger style round nose bullets that are not compatible with the 357 sig bottle neck case. The 38 super does not have this disadvantage. To muddy the water a bit, many 38 super chambers will in fact allow the reloading of .357 bullets as well because the outside diameter between a .355 and .357 bullet is miniscule. A lot of 110 and 125 grain bullets intended for use in 38 and 357 revolvers can be successfully used to reload 9mm and 38 super cartridges. I've played around a bit with 158 SWC bullets out of 9mm Luger so I'm not just speaking hypothetically but from experience. I've also built a couple of swap barrel 1911s that can use 9mm Luger and 38 Super cartridges with a barrel and magazine swap. I didn't need a new slide, just an extractor adjustment to make sure 9mm had enough case tension to extract reliably.
 
Converting my Sig 226 from .357 Sig to .40 is nothing more than a barrel swap. Same mags. I thought they may share the same case? Never looked it up to be sure but if that is true, the .40 is just a necked down 10mm.

Seems like this would be an easy modificaiton.
 
rc said:
Gary, the topic is caliber swaps and the 1911. There are basically two breech face cuts for 1911s I would characterize as the 38 super cut and the 45 cut. Some people would argue there are really 3 or 4 different breech face cuts including 9mm, 38 super, 10mm and 45 but I would argue it's more about extractor adjustments than breech cuts when case heads are close in size.
Click to expand...
It's not that "some people would argue" that there are three or four breech cuts. The ARE at least three -- it's just that not all manufacturers bother to use them.

Caspian Arms uses three breechface cuts: .45 ACP, .40/10mm, and 9mm/.38 Super.

Para-Ordnance, on the other hand, only used two: one for .45 ACP, and the other for everything else. And I know it can work, because I built a 9mm pistol using a surplus Para .40 S&W slide and a surplus Para 9mm barrel. So far, it has functioned flawlessly.

The fact that not all manufacturers limit themselves to two breechface cuts doesn't mean that it's a myth that others make a finer distinction.
 
I don't think anybody was talking about fire forming 357 Sig from either 40 S&W or 38 super.
 
gmarr said:
Ok, I like them both, and have both. So that got me thinking about converting my 10mm 1911 to 357 Sig. From what I've read it's pretty easy. Barrel and recoil spring. Anyone done this or know what else is needed?
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Yes.

It has been more than a year since my 10mm DW Silverback launched a 10mm projectile. I love 10mm, but 357Sig has been a blast from this platform.

Fit barrel, recoil spring and a briley spherical bushing for the 357Sig swap. And the 357Sig has run flawlessly from my Tripp Cobra 10mm mags.

Roll your own 'cause them lil' 357Sig cartridges are ridiculously 'spensive.

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Aguila Blanca said:
Para-Ordnance, on the other hand, only used two: one for .45 ACP, and the other for everything else. And I know it can work, because I built a 9mm pistol using a surplus Para .40 S&W slide and a surplus Para 9mm barrel. So far, it has functioned flawlessly.
Click to expand...

Para has used three slide cuts. I have a p18-9 9mm slide and it will not accept 40/10mm cases.
 
Are you hand loading? Might also consider the 9x25 Dillon if the goal is to just have a speedy 9mm launched from a 1911...
 
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