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View Full Version : 40 cal out of 10mm barrel


oldschool88
04-21-2011, 5:59 PM
So I just came from the gun store and had a rather interesting conversation with an employee there. He claims to have a Glock 20 with the stock 10mm barrel. And he claims to have near 1000 rounds of 40 cal fired through it without a problem. He said it puts extra strain on the extractor but thats it. This sounded wrong to me, and I would rather ask than find out the hard way on my Glock 20.:D

pontiacpratt
04-21-2011, 6:00 PM
Isn't a 10mm round a little bit longer than a .40? that cannot be good for it

oldschool88
04-21-2011, 6:02 PM
Yes, 40 is shortened 10mm...the resulting gap is my concern.

AJAX22
04-21-2011, 6:11 PM
It's do-able

It just headspaces off the extractor instead of the case mouth.

There was actually one pistol design which was intended to interchange 40 and 10mm (it had dual extractors iirc)

elSquid
04-21-2011, 6:16 PM
It's do-able

It just headspaces off the extractor instead of the case mouth.

There was actually one pistol design which was intended to interchange 40 and 10mm (it had dual extractors iirc)

Springfield Omega? I was always curious about that one...

-- Michael

Turo
04-21-2011, 6:25 PM
It can, and most likely will do it. He would probably have issues extracting 10mm if he shot them right after shooting a bunch of 40S&W though, same issue as shooting .357mag right after a bunch of .38.

It's definitely not recommended, and besides, conversion barrels are only about a hundred bucks. But, the 10mm is designed for more powerful rounds, so I don't see any safety issues there, maybe accuracy because of the bullet jumping from the 40 casing, but it doesn't sound too bad, .142 inches.

Davidoff
04-21-2011, 6:31 PM
It's do-able

It just headspaces off the extractor instead of the case mouth.

There was actually one pistol design which was intended to interchange 40 and 10mm (it had dual extractors iirc)

This is exactly correct.

Most cartridges designed for semi-auto pistols headspace on the case mouth, including 10mm and .40S&W. Shooting a much shorter .40S&W in a much longer 10mm chamber means that the only thing stopping the loaded round from going down the barrel is the extractor. Not good, and will probably lead to extractor failure and a loaded round stuck in the chamber. If the gun shop guru has fired 1000 rounds of .40S&W through his 10mm barrel, he has been pretty lucky.

sirgiles
04-21-2011, 6:37 PM
extractor failure will eventually happen. i just wonder what will happen to his hand when it occurs.

Cali-Shooter
04-21-2011, 6:45 PM
It can, and most likely will do it. He would probably have issues extracting 10mm if he shot them right after shooting a bunch of 40S&W though, same issue as shooting .357mag right after a bunch of .38.

What's wrong with shooting .357 mag out of a .357 revolver right after the revolver shot a bunch of .38 spl rounds then ejected the casings? Any issues of switching ammo types so soon right after each other?

Turo
04-21-2011, 6:50 PM
What's wrong with shooting .357 mag out of a .357 revolver right after the revolver shot a bunch of .38 spl rounds then ejected the casings? Any issues of switching ammo types so soon right after each other?

It's not really a timing issue, it's just that since the 38 casing is shorter than the .357 casing, It leaves a ring of carbon at the end of the cylinder, and then the 357 casing expands into that carbon and makes it harder to extract. The issue would be compounded by the 10mm/40S&W because the only thing pulling the 10mm casing out would be the recoil of the slide, which might not be enough force if it's stuck on that carbon ring.

It's not a safety issue or anything, just an inconvenience issue, and maybe a jamming issue. Nothing's necessarily wrong with it, it's just harder to extract, but on a semi-auto, it might be hard on the extractor.

Cali-Shooter
04-21-2011, 6:59 PM
^ ^ ^ There is so much to firearms, I learn something new every day, I swear, heh. Thanks for all the info, great to know all this pertinent data.

Munk
04-21-2011, 8:10 PM
It's not really a timing issue, it's just that since the 38 casing is shorter than the .357 casing, It leaves a ring of carbon at the end of the cylinder, and then the 357 casing expands into that carbon and makes it harder to extract. The issue would be compounded by the 10mm/40S&W because the only thing pulling the 10mm casing out would be the recoil of the slide, which might not be enough force if it's stuck on that carbon ring.

It's not a safety issue or anything, just an inconvenience issue, and maybe a jamming issue. Nothing's necessarily wrong with it, it's just harder to extract, but on a semi-auto, it might be hard on the extractor.

I've seen this carbon ring issue first hand. Although it was with a .44special/mag. Extraction is considerably more difficult after only a few rounds fired through each of the chambers.

I saw the thread title and cringed. If he really wants to shoot .40s&w out of it, he can just shoot reloaded 10mm. I've seen the recipes... they often just use a .40 recipe for the 10mm loads. Thats... just... so... weak.... and I'm also dissapointed at the waste of a fun machine like a glock20. It WANTS to eat that scorching hot loaded 10mm... and he's feeding it rabbit turds (I say this as a shooter who's current fave eats .40s&w lol).

wamphyri13
04-21-2011, 9:33 PM
Springfield Omega was available in 3 calibers. 10mm, .38Super, and .45ACP.
Yes it had dual extracors for this, but .40S&W was not one of the calibers.

Big difference in comparing .38/.357 and .40/10mm. On the semi-auto, the case seats at the rim of the case. Shorter case, seats farther forward, not good for extractor. On the revolver, base prevents shorter cartridge from going too far forward, so shorter case can be used without trouble.
Ryan