40SW

[Grizzz]

Nobody makes a conversion barrel (40sw) for a g-21?  But they do for a g20 

[sqlbullet]

There is another thread that is dealing with the same root issue.

Extractor groove diameter of the 9mm, 40S&W and 10mm is all the same:  .340".  The 45 ACP is .400".  This makes downsizing a 40 to 9mm easy, but 45 to 10 or 40 a challenge because the extractor may not reliably grab the rim.

You should look for a glock 20 barrel short chambered  in .400"  This could be finish reamed to either 40 S&W or 10mm.  Might have to call around to the various makers, but I bet Storm Lake or Lone Wolf could make one for you very easily.  That is how they have to start.

[Grizzz]

I was reading somewhere that the gen 3  g21's had a updated  extractor that works well with 10mm conv. that i already have in my g21. I was hoping to conv. the g21 to 40sw also.

[dougx]

Aren't the barrels interchangeble?G20  should fit the g21,so any barrel that fits g20 should fit the g21,correct?

[DM1906]

Aren't the barrels interchangeble?G20  should fit the g21,so any barrel that fits g20 should fit the g21,correct?

The barrels will "fit", but the 10mm case head doesn't fit the G21 breach, and the extractor won't engage.  It'll need a G20 slide (which also fits), or modification (extractor).

[Grizzz]

Gee! Haven't had any problems with my g-21 slide.   

[DM1906]

Gee! Haven't had any problems with my g-21 slide. 

Me neither, but I wouldn't rely on it.  "It works" is a long way from practical.

[The_Shadow]

I think the 10mm conversion barrels made for the G-21's have a larger diameter at the muzzle to accomedate the opening in the slide where the barrel sticks out.    No barrel bushing in the Glock...  
Someone correct me if this is incorrect!

[DM1906]

I think the 10mm conversion barrels made for the G-21's have a larger diameter at the muzzle to accomedate the opening in the slide where the barrel sticks out.    No barrel bushing in the Glock...  
Someone correct me if this is incorrect!

The 10mm barrel will fit with a barrel bushing.  I haven't heard of anyone using them in years, since the increased availability and lower cost of aftermarket barrels that just fit and shoot.  I was referring to a 10mm conversion barrel I had and sold, addressing the extractor issue.  For maximum versatility, one frame, both slides, and a healthy collection of barrels and springs is the best way to go.  It'll give the option of shooting everything from 9mm to 45 Supers, and everything in between.

[Grizzz]

So, if i bought a 10mm long slide, would it fit my G-21 frame?

[sqlbullet]

Yes.  The uppers and lowers are interchangeable between g20 and g21.

[REDLINE]

So, if i bought a 10mm long slide, would it fit my G-21 frame?

Do you think you are going to give it a go?  As sqlbullet said it shouldn't be an issue whatsoever.  I'll be interested to know if it turns out for you if you do.  Certainly keep us posted if you move forward with it.

[Yondering]

I think the 10mm conversion barrels made for the G-21's have a larger diameter at the muzzle to accomedate the opening in the slide where the barrel sticks out.    No barrel bushing in the Glock...  
Someone correct me if this is incorrect!

The 10mm barrel will fit with a barrel bushing.

No, not correct. The G20 and G21 barrel diameters are the same. No barrel bushing needed. 

The only external dimension that's different between a 20 and 21 barrel is the barrel hood, which is narrower on the 20 barrel. A 20 barrel fits a 21 slide fine; the rear of the barrel is located by the sides of the slide, not the barrel hood, but that doesn't seem to matter.

The gen 3 G21 extractors do engage the 10mm and 40 S&W case heads as well. Sliding a 10mm case under the extractor on a 21 slide seems like it's too loose, but when the case is located by the barrel, it works fine. Mine functions 100% with 10mm and 40 S&W with a G20 barrel in the G21 slide. The only difference I've noticed is sometimes brass is ejected back over my head instead of out to the side.

To answer the OP, you can use a G20 40 S&W conversion barrel in the G21 slide with no other modifications, and it will work. You'll have to use g20 mags of course. You could also just use a 10mm barrel and shoot 40 S&W in it, no need for the conversion barrel; this is ok in a Glock only.

[Yondering]

So, if i bought a 10mm long slide, would it fit my G-21 frame?

Yes. That's what mine is.

[DM1906]

No, not correct. The G20 and G21 barrel diameters are the same. No barrel bushing needed.

You're right.  Brainfart.  Like I said, many years ago.  May have been first gen vs. 2, or another caliber.  Tried the Gen2 21 and Gen3 20 a few days ago, and they fit.  A couple FTF's with the 10mm barrel in the 21 with 21 slide, but shot well otherwise.