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Old 07-23-2012, 12:01   #1
orangeride
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Glock 21 conversion to .40?

I've been shooting the crap out of my g20 with a .40 conversion. Ive also got a 23 with a 9mm conversion. As you can see I'm into versatility. I saw that some guys have been converting .45's to 10mm's. I know a 40 is just a shorter 10. Do you guys know of anybody making a 45-.40 conversion? Ya I know I'll need to use my 10mm mags.
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Old 07-23-2012, 13:20   #2
GRT45
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I'm not aware of any manufacturer offering a 45-40S&W Glock conversion barrel, but the following paragraph I wrote about a G30 conversion to .40S&W using a G29 10mm-40 conversion barrel might also be true for the G21 with a G20 10mm-40 conversion barrel.
Although conversion barrels for the Glock 29 10mm pistol are intended by the manufacturer for use in the G29 only, others have reported successfully shooting .40S&W in the G30 slide using a G29 10mm-40S&W conversion barrel. This is feasible since there is only .050" difference in the narrower width of the G29 10mm barrel chamber hood compared to the G30 45ACP barrel hood. Having acknowledged that a G29 OEM 10mm barrel functions in the G30 slide and accuracy remains good, one can accept that a G29 conversion barrel will function in the G30 slide. I do not claim this is recommended, but the possibility is certainly intriguing. For reference, conversion barrels for the G29 10mm pistol are available for .40S&W, .357Sig, and 9x25Dillon.
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Last edited by GRT45; 07-23-2012 at 16:58..
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Old 07-24-2012, 00:18   #3
Yondering
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You don't need a conversion barrel. You can use the G20 10-40 conversion barrel in your 21 if you want, as Grt45 said above, or you can just use your G20 stock barrel in your G21, and shoot .40 through it. I regularly use a aftermarket (LW) G20 barrel in my G21 (with a muzzle brake to reduce slide speed).

You don't need a 10-40 conversion barrel in a Glock, there are no problems shooting 40 S&W in the 10mm barrel for practice, other than cleaning the chamber before shooting 10mm again, if you've fired a lot of rounds of 40. The danger of firing a round that jumped in front of the extractor does not exist in a Glock, like it does in other guns; the Glock firing pin is too short.

Last edited by Yondering; 07-24-2012 at 00:20..
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Old 07-24-2012, 22:30   #4
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Due to the differences in breachface width (45 vs 10mm/40), would it cause any lateral movement of the barrel? Is there any possibility of damage to the gun? I've always been told it won't work, but I know GRT45 & Yondering know what they're talking about, so I'm curious about that.
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Old 07-24-2012, 23:27   #5
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Quote:
Originally Posted by Meathead9 View Post
Due to the differences in breachface width (45 vs 10mm/40), would it cause any lateral movement of the barrel? Is there any possibility of damage to the gun? I've always been told it won't work, but I know GRT45 & Yondering know what they're talking about, so I'm curious about that.
I've fired thousands of .40 rounds in the G20, with 10mm (non-conversion) barrels, OEM and aftermarket. I haven't shot many in the G21 (a couple hundred), and the OEM 10mm barrel. No indication of any problems in either. Very consistent and reliable (for target/plinking, NOT carry), but please do heed the warnings about cleaning after. Bullet and powder fouling will collect in the chamber. Harmless, but must be addressed.
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Old 07-25-2012, 00:03   #6
Meathead9
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Originally Posted by dm1906 View Post
I've fired thousands of .40 rounds in the G20, with 10mm (non-conversion) barrels, OEM and aftermarket. I haven't shot many in the G21 (a couple hundred), and the OEM 10mm barrel. No indication of any problems in either. Very consistent and reliable (for target/plinking, NOT carry), but please do heed the warnings about cleaning after. Bullet and powder fouling will collect in the chamber. Harmless, but must be addressed.
I know it's a lot less risky to shoot 40 through a stock G20. The only real issue there is free-bore, but it doesn't seem to be much of a problem.

My question was based on the statement that it's possible to put a G29 barrel in a G30 slide, or a G20 barrel in a G21 slide, and shoot 10mm safely. I've never done it, so I'm curious to hear what kind of problems can occur in that situation. Im not doubting it, I've just always been told different.
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Old 07-25-2012, 00:13   #7
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Quote:
Originally Posted by Meathead9 View Post
I know it's a lot less risky to shoot 40 through a stock G20. The only real issue there is free-bore, but it doesn't seem to be much of a problem.

My question was based on the statement that it's possible to put a G29 barrel in a G30 slide, or a G20 barrel in a G21 slide, and shoot 10mm safely. I've never done it, so I'm curious to hear what kind of problems can occur in that situation. Im not doubting it, I've just always been told different.
I've also heard you shouldn't do it. But, never any real reason, other than you shouldn't. It does sound counterintuitive, but I don't know of anyone who has done this, including me, who has any problem with it to report. Absolutely, don't do it!! But if you do, nothing bad will likely come of it. Also, DON'T run with scissors, and kissing makes you pregnant. (one of those is probably good advice....pick one)
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Old 07-25-2012, 00:18   #8
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The stock G20 barrel will fit in the G21 slide. There is about 5-6 mil clearance on either side and up where the barrel locks into the slide in the rear there is maybe .025" clearance on either side, this leads to a small amount of looseness when just the barrel and slide are fitted together but doesn't seem to affect lockup. The lighter slide on the G21 wouldn't be a problem for .40S&W's shot out of the 10mm barrel. The only glitch I could see cropping up is the extractor. On the G21 slide the extractor claw is not going to be protruding as far in, so you might have some extraction failures.
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Old 07-25-2012, 00:44   #9
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Originally Posted by WeeWilly View Post
The stock G20 barrel will fit in the G21 slide. There is about 5-6 mil clearance on either side and up where the barrel locks into the slide in the rear there is maybe .025" clearance on either side, this leads to a small amount of looseness when just the barrel and slide are fitted together but doesn't seem to affect lockup. The lighter slide on the G21 wouldn't be a problem for .40S&W's shot out of the 10mm barrel. The only glitch I could see cropping up is the extractor. On the G21 slide the extractor claw is not going to be protruding as far in, so you might have some extraction failures.
I thought that (extractor), at first, but it worked when I tried it. I was skeptical until I actually tried it. As far as the breach goes, it's a non-issue. The 10mm OEM chamber is tighter than the 10mm breach clearance (same with the .45). So, in any case, whatever play there is, will be taken up by the chamber. The case will straighten up, or it won't lock in, and won't fire. I haven't seen that happen, but not saying it can't. Whatever the case, don't do what isn't comfortable. If you don't feel good about shooting them, then don't. BTW, .40S&W in a 10mm barrel, G20 or G21 slide, is remarkably accurate. More so, I think, than the pistol designed to shoot the cartridge (G22). Maybe the heavier/larger frame is more stable, but it is what it is.
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Old 07-25-2012, 00:45   #10
Meathead9
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Quote:
Originally Posted by WeeWilly View Post
The stock G20 barrel will fit in the G21 slide. There is about 5-6 mil clearance on either side and up where the barrel locks into the slide in the rear there is maybe .025" clearance on either side, this leads to a small amount of looseness when just the barrel and slide are fitted together but doesn't seem to affect lockup. The lighter slide on the G21 wouldn't be a problem for .40S&W's shot out of the 10mm barrel. The only glitch I could see cropping up is the extractor. On the G21 slide the extractor claw is not going to be protruding as far in, so you might have some extraction failures.
Thanks Willy. That definitely helps me understand why it's probably not a big deal. I love it when something I've been told over an over by expert theory, is proven to be wrong by people that have actually had the stones to try it.
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Old 07-25-2012, 10:41   #11
Yondering
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Quote:
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Due to the differences in breachface width (45 vs 10mm/40), would it cause any lateral movement of the barrel? Is there any possibility of damage to the gun?
When using a 20 barrel in a 21 slide, the back of the barrel is located laterally by the sides of the slide, instead of the barrel hood. In my 21, this doesn't seem to allow any more lateral play than with the stock 21 barrel installed.

No damage will happen to the gun. My slide had a burr at the bottom rear of the ejection port that left a mark on my 10mm LW barrel, but it hasn't gotten worse after removing the burr.

One thing to keep in mind is the lighter 21 slide; if you're running full power 10mm loads in a 21 slide, without a muzzle brake, you could have issues from high slide speed, and possibly early unlocking. Using a muzzle brake, or not using full power 10mm loads, fixes that issue.

I agree that .40 in the 10mm barrel shoots really well, with both cast and jacketed bullets.
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