Glock 21: 10mm and 40 S&W?

[smythe012]

I've been looking into a G21 to use in 45 ACP, and also convert to 10mm. I've read enough reviews that confirm the 10mm is no problem (conversion barrel, recoil spring, extractor, mags), but it has me wondering: the frame of the 20 and 21 are exactly the same. The slide of the 20 is a little more stout but the 21 is similar enough to be converted to 10mm.

Why would the Glock 20 conversion barrel to 40 S&W not also work? If I replaced the recoil spring and extractor from the 21, would it be dissimilar to the 20?

I have to be missing something.

 

[IndyGlockMan]

40 cal mags won't work in the large frame.
you could put 40 ammo into the 10mm mag (same diameter casing), but you'd likely have feeding issues.
I don't think anybody makes a 40 cal conversion barrel for the 20/21 large frame anyway.

Just get a police trade G22/40 cal. They can be had for $325-350

 

[smythe012]

I've used 10mm mags and a lone wolf 10-40 conversion barrel in a G20, fortunately with zero feeding issues using 40 cal ammunition.

 

[Compatriot G]

Military Arms Channel has a video up on the 10mm cartridge. He loaded an S&W 1076 with .40 S&W and it ran all 9 rounds without a single malfunction.

 

[WILSON]

Not proud of this at all (it's actually kind of embarrassing to admit), but...

I accidentally found out my G-20 (gen-3) runs okay on 40 S&W ammo (180gr WWB FMJ's) a few years ago.
I was using the 20 and a 40 cal FNP ... and accidentally (stupid and careless, I know) loaded one G20 mag with 40's.




Not sure if there's anything especially dangerous about it (the 10mm barrel on the 20 is THICK), but I'll never do it again because of reliability concerns. Much more importantly, the only way it can work is; the extractor alone must've been holding the shell against the breech-face tight enough to get adequate firing pin strikes.
That has to be tough on the extractor! I doubt if it'd take long for the extractor to fail/bend/break.


(I've hears similar stories about using 380ACP in a G17 in an emergency, but I've never tried it)

 

[billybob44]

I don't think anybody makes a 40 cal conversion barrel for the 20/21 large frame

I have had a Lone Wolf Stainless .40 S&W conversion barrel in my G-20, 10MM for awhile..Works GREAT...Bill.

 

[WILSON]

I have had a Lone Wolf Stainless .40 S&W conversion barrel in my G-20, 10MM for awhile..Works GREAT...Bill.

Do normal 10mm mags work, or did you have to switch to G-22 mags?

 

[Amishman44]

40 cal mags won't work in the large frame. you could put 40 ammo into the 10mm mag (same diameter casing), but you'd likely have feeding issues. I don't think anybody makes a 40 cal conversion barrel for the 20/21 large frame anyway. Just get a police trade G22/40 cal. They can be had for $325-350

I've used 10mm mags and a lone wolf 10-40 conversion barrel in a G20, fortunately with zero feeding issues using 40 cal ammunition.

The .40 will work in the G-20 but there's no conversion barrel down to .40 for the G-21 slide. You can pick up a Lone Wolf G-20 slide + whichever barrels you choose and build a separate slide that will let you shoot 10mm, .40, .357SIG + a few others just by changing the barrel out. You'd have a nice variety pack anyhow!

 

[Amishman44]

Do normal 10mm mags work, or did you have to switch to G-22 mags?

You would have to use the 10mm mags as the G-22 mags won't function in the larger G-20 frame.

You're asking questions, though, and that's a good thing!

Keep diggin'...

 

[smythe012]

The .40 will work in the G-20 but there's no conversion barrel down to .40 for the G-21 slide. You can pick up a Lone Wolf G-20 slide + whichever barrels you choose and build a separate slide that will let you shoot 10mm, .40, .357SIG + a few others just by changing the barrel out. You'd have a nice variety pack anyhow!

The conclusion is that with this barrel, a 10mm extractor, recoil spring and magazines, it still won't properly function in a G21 slide?

I think the answer is "yes it doesn't work," and all those conversions you mentioned above are exactly why I want a Gen 4 G20!

 

[smythe012]

Anybody in NWI feel like using their G21 as a Guinea pig? Anyone?

 

[WILSON]

Anybody in NWI feel like using their G21 as a Guinea pig? Anyone?

I have a (more or less) LNIB one, and IIRC, we may or may not have met a few times.

Are you gona blow my 45 up at Willow Slough?

 

[smythe012]

Maybe? I already have the conversion barrel from an old 20; the question is will I be using it in a new Gen 4 20 or watching it detonate, er, function in a new 21.

 

[Hohn]

Do normal 10mm mags work, or did you have to switch to G-22 mags?

G20 mags feed .40 perfectly. G22 mags will not work properly in a G20.


The main obstacle I see is if the G21 slide has a larger hole in front than the G20 slide does. I've never compared them. But I think a G21 barrel would be impossibly thinwall in a G20 slide cutout, so I strongly suspect that the G21 slide has a larger cut.

Which means that using a G20 barrel-- and any conversion for it-- will be pretty inaccurate in the G21 slide.

It's possible the slides are the same (except extractor/ejector), in which case the G20 barrels will work OK if you have other supporting parts.


Most people I know who get into this just get a second slide for the G21-based stuff and the G20 based stuff, because there are so many conversion options from 10mm and .45.

 

[two70]

G20 mags feed .40 perfectly. G22 mags will not work properly in a G20.


The main obstacle I see is if the G21 slide has a larger hole in front than the G20 slide does. I've never compared them. But I think a G21 barrel would be impossibly thinwall in a G20 slide cutout, so I strongly suspect that the G21 slide has a larger cut.

Which means that using a G20 barrel-- and any conversion for it-- will be pretty inaccurate in the G21 slide.

It's possible the slides are the same (except extractor/ejector), in which case the G20 barrels will work OK if you have other supporting parts.


Most people I know who get into this just get a second slide for the G21-based stuff and the G20 based stuff, because there are so many conversion options from 10mm and .45.

You are correct, the G21 slide has a larger cutout. A G20 barrel would be pretty sloppy in G21 frame. I'm sure it would fire but I doubt it would be very reliable.

 

[88E30M50]

I thought there was a thread not long ago about how a Glock G20/G29 can run .40 without an issue and that running .40 out of a 10mm Glock was pretty common. If that would work fine, then I don't see any reason that a G21 with a Storm Lake 10mm conversion barrel might not run .40 fine as well. My guess is that is why there are no .40 conversion barrels for the G21. If .40 works in a 10mm barrel, then why not just run that?

 

[Sling10mm]

So the G21 extractor and ejector are compatible with a 10mm/40 S&W/357 SIG cartridge?

 

[Hohn]

So the G21 extractor and ejector are compatible with a 10mm/40 S&W/357 SIG cartridge?

Not to my knowledge.

I I had a .40 conversion barrel for my g20. And I also ran .40 in the 10mm barrel.

The .40 runs perfectly in the stock g20. The only downside is that the poorer gas seal makes it run dirty and you'll lose 50 fps or so. Big deal. In hindsight, I'd spend the money again for the conversion just because I ended shooting mostly .40sw.

 

[in625shooter]

Military Arms Channel has a video up on the 10mm cartridge. He loaded an S&W 1076 with .40 S&W and it ran all 9 rounds without a single malfunction.

I was stationed in Montana in the early 90's. Around 92 we hosted a pistol match for Police week with several LEO'S around the state.

One guy let his son pack his range bag (???? As to why) but he packed 40 ammo and the guy had a S&W 1076. He tried shooting the match unbeknown to us until he started having problem. We were all sort of baffled as to why it kept jamming then his story came out. We had no choice but to remove him. We did let him back in after he ran to a local gun shop and got 10mm ammo.

10 mm was really popular in Montana with LE agencies. Billings issued it at one time.Yellowstone county Sheriff department (around Billings)still carries (or did) the Glock 20 in 10mm.