.40 S&W in a 10mm?

[astocks2622]

I was just wondering if it's safe to shoot .40 ammo through my 10mm. I know the .40 was developed from the 10mm, and that they are very similar except for OAL. A buddy has an M&P .40, so i took some of his ammo and slowly hand racked it through my 10mm. it fed and eject the entire mag with no problems. what do you all think?

 

[Gas Operated]

I think that's not good for the extractor.
On the other hand, if your 10mm is a Smith 610, shoot all the .40 you want.

 

[ZeSpectre]

I think that autoloaders headspace on the rim.
Not a good idea.

I swear I'll never understand why people want to shoot ammo out of guns that aren't chambered for that ammo. Hrmmmm, let's take this tightly controlled explosion and dink around with it.

 

[rcmodel]

NO, it may be possible, but it's not safe.
And it would be very hard on a gun.

A .40 case is too short to headspace properly in a 10mm chamber.

So the firing pin would drive it forward until the extractor hook stopped it.
At that point, if it fired, the case would get a very high-speed running start before it slams back into the breach-face.

If it would feed, and if it went off, it would batter the gun unmercifully!

rcmodel

 

[JohnKSa]

The extractor has to hold the case in position for the firing pin to strike the primer. That puts extra stress on the extractor, and in some cases the extractor may not be up to the task. That issue can cause misfires and some possibility of an extractor failure.

You can also get the typical carbon ring buildup which may cause malfunctions when you go back to the proper caliber.

A much more dangerous (though admittedly less likely) situation can arise if the sharp edge of the chamber (where the chamber transitions to rifling) shaves off bullet material. In a revolver, there is a smooth taper in front of the case mouth so that this doesn't happen, that's why it's safe to shoot shorter cartridges in a revolver. In an autopistol, there's typically a sharp lip in front of the cartridge mouth which the front of the case bears against to establish headspace. If you're shooting the right length cartridges in the chamber, the bullet never touches that lip, but if you shoot shorter cartridges in the chamber, small amounts of bullet material can be shaved off at each shot and build up at the front of the chamber. Eventually that material could build up enough to cause a bore obstruction.

 

[antsi]

Agree with the above; one addition: many 10mm semiautos can be safely adapted to shoot .40 SW by getting a conversion barrel that is chambered in .40 SW. This way, the new barrel has a chamber of the correct dimensions. You might possibly have to change to a weaker recoil spring as well. Depite the expense of the new barrel, there are some advantages to this if you can get less expensive ammo for range use.

 

[Coronach]

As was stated, it may work, but it's not a very good idea.

Mike

 

[MachIVshooter]

I've done .40 in 10mm's and .45 GAP in .45 ACP's. They'll fire, they won't feed reliably, and honestly there's really no good reason to do it.

I did it just because, but it's not something I feel the need to do again.

 

[astocks2622]

ok, that's what i kinda of figured. i have a witness in 10mm that just cracked the slide (huge bummer), and am looking at the glock 20 to replace it once i get rid of the witness. i did hear that you can get the normal glock .40 barrel that should fit the 10mm slide just fine for practice, then switch back for woods use. any problems there?

 

[treeprof]

You'll need a purpose-built conversion barrel to shoot .40 in your G-20; you cannot take a barrel out of a .40 caliber Glock and drop it in a G20. Barsto, Lone Wolf, KKM, etc. make the conversions. I use KKM in mine.

 

[BattleChimp Potemkin]

What kind of 10mm do you have? If it is a 1911, change you barrel (and magazines?) and you have a .40 SW 1911. I did that b/c the police use our range during the week and leave a ton of unfired .40 in the brass bin and a blessing from them to pick it out for our uses. (smallest guy at our range, so they give me a flashlight and a .45, into the bin I go ). Gives me alot of reason. As for Glocks, isnt there a frame issue that wont allow for it?

 

[sqlbullet]

It is NOT safe, and here is why.

The bullet leaving the 40S&W cartridge has to swipe past the headspace shoulder in the chamber. It will foul this shoulder with copper or lead (depending on Ammo). As the fouling builds from repeated firing you have two dangers.

1. 10mm cartridges will no longer headspace properly.
2. The builup creates a 'throat', or narrow spot, in the barrel that the bullet must pass, causing pressure spikes.

Bar-Sto and others make drop-in conversion barrels for most 10mm guns to 40 S&W. Prices run up to about $200. Imagine for a moment you are standing at the range blind with shredded hands, and ask if you would pay $200 at that point to have your sight and hands back.