Making a G21 into a G20?

[1lostinspace]

I heard all you need is a barrel. will the 45ACP mags fit 10mm? or do I need new mags? Do I need a guide rod and different spring?

Thanks guys

[AleksT]

From what I've found the minimum you'll need is the conversion barrel and G20/10mm magazines. I just picked up my G21SF yesterday and I have the KKM conversion barrel and 2 x G20 mags. I plan on going to the range tomorrow and trying it out with 10mm.

I've also "read" on forums that you can swap in a stock Glock G20 barrel into the G21 but the shrouds aren't quite the correct size. One member claims to have done it and says it still shoots accurately for him but I'm not too comfortable doing that.

Hope that helps.

[1lostinspace]

From what I've found the minimum you'll need is the conversion barrel and G20/10mm magazines. I just picked up my G21SF yesterday and I have the KKM conversion barrel and 2 x G20 mags. I plan on going to the range tomorrow and trying it out with 10mm.

I've also "read" on forums that you can swap in a stock Glock G20 barrel into the G21 but the shrouds aren't quite the correct size. One member claims to have done it and says it still shoots accurately for him but I'm not too comfortable doing that.

Hope that helps.

Let me know what happens, I heard you need to replace the recoil spring as well. It makes sense the 45ACP would not recoil as hard!

[NickN27]

You need the specific barrel 45 slide / 10mm, mags and I would get a diff recoil spring for 10mm its a little hotter depending the load.

[stormy_clothing]

The dual spring and navy spring cup set up is nice with the KMM barrel, make sure you break in the action a whole bunch of times to avoid lock up at the range.

[AleksT]

1lostinspace - I just got back from the range and I have some results. First of all, I was using my brand new G21SF with several different ammo. I'll try and break it down for you so it so it makes some sense.

The entire session was shot with my G21SF with a LWD stainless steel guide rod w/17lb spring. The differences were barrel used and ammo.

Barrel - Stock (.45acp)
Ammo - Speer 230 gr. ball (50 rounds)
Ammo - Hand Loads (50 rounds)
Result - 100% reliable

Barrel - LWD G21 (.45acp)
Ammo - Hand Loads (50 rounds)
Result - 2 FTE

Barrel - KKM 10mm conversion (Part # G21G1)
Ammo - Hornady 180gr XTP (20 rounds)
Result - 2 FTE & 1 FTF

Barrel - KKM 10mm conversion (Part # G21G1)
Ammo - Hornady 200gr XTP (20 rounds)
Result - 4 FTE

The stock G21SF worked great and was pretty accurate once I sighted in (Dawson Precision adjustable sight). My hand loads felt much lighter as I was using 200gr RN bullets but once I was used to that it was just as accurate if not more than the Speer rounds.

Once I moved to 10mm I could definitely feel the difference in recoil. When I was shooting the 180gr rounds the recoil felt as stout as the 230gr Speer rounds but with sharper feedback within the pistol frame itself. It seemed like I could feel the explosion more with the 10mm but it wasn't bad. I did notice that some of the brass was pretty damaged after it ejected but this wasn't consistent with every round - just a few.

When I moved to the 200gr 10mm rounds I could definitely feel even more recoil than with the 180gr bullets but it was manageable. Since I only fired 20 rounds of each weight Hornady I will accept the possibility that I might have been limp wristing and it could have caused the FTEs. But it wasn't consistent and it even happened when I made an effort not to limp wrist.

I'll have to give it another run but next time I'll try shooting 10mm only. This might help reduce flinching or limp wristing. As far as accuracy is concerned it seemed like the 180gr Hornadys were more accurate for me and at 10 yards it shot about 1" left. I'm still pretty happy with the results (for now) but I'd like to get around 500 rounds through Glock first.

10mm is a stout round for sure but I think with some practice it would be totally manageable and a great performer. I'm just used to shooting .45acp in 1911s so that may also be a factor with the FTEs. Now I want to shoot something other than paper now.

[Oceanbob]

Thanks for the Update..

Very good information. Is your ejector modified for the 10MM barrel/round?
(grind the bump off?)

[AleksT]

No I haven't modified the ejector on my G21. I read in another thread about that but I don't know exactly what to do or which bump to grind off. I'd like to do that if helps save my brass as it would make me want to shoot it more if I didn't have to replace brass as often.

A huge benefit of shooting .45acp is that brass lasts longer and saves you money to shoot more often. It seems like the brass lasts a long, long time as long as you don't lose it.

[cortayack]

Good information, thanks

[1lostinspace]

I ll stick with the 45ACP thanks for your info Alekst

[icentropy]

No I haven't modified the ejector on my G21. I read in another thread about that but I don't know exactly what to do or which bump to grind off. I'd like to do that if helps save my brass as it would make me want to shoot it more if I didn't have to replace brass as often.

A huge benefit of shooting .45acp is that brass lasts longer and saves you money to shoot more often. It seems like the brass lasts a long, long time as long as you don't lose it.

Well i'm picking my G21SF up tomorrow. I hope to have the KKM G20 conversion barrel and mags by wednesday. I'll be taking it to the range on Tuesday just to run it as a 45 and make sure everything is working as it should. Then i'll modify the extractor and shoot it as a 10mm and 45 by the end of the week. I'll post what results the modification had.

Alekst, did you end up grinding that tab off yet?

[AleksT]

I didn't grind it off yet. I have to take a look at it and see if it's really obvious to me. Otherwise, if I had a picture of what I need to grind off that would help. I guess I might call KKM and ask. The few FTEs I experienced the case mouths were badly dented by that was probably from the slide slamming back down on the brass (makes sense now that I think about it).

To be fair I feel I need to try this again but this time only shooting 10mm and ensuring I have a firm grip and no limp wristing it. For the next exercise I won't care about accuracy (yet) as I'm currently concerned about reliability. Once I have that then I'll work on accuracy.

Let me know how your range session goes and I'll report back mine this week as well. I know you described what I need to grind off in the other thread but if you could show me (pic?) I would greatly appreciate it. As long as it's a replaceable part then I won't worry about grinding it off since if it didn't work I'd just replace the part. But if I can be sure about what to do, I'll give it a shot.

-Aleks

[icentropy]

Let me know how your range session goes and I'll report back mine this week as well. I know you described what I need to grind off in the other thread but if you could show me (pic?) I would greatly appreciate it. As long as it's a replaceable part then I won't worry about grinding it off since if it didn't work I'd just replace the part. But if I can be sure about what to do, I'll give it a shot.

-Aleks

Sounds good, I'll be sure to take before and after pics of the extractor.

[AleksT]

icentropy - thank you! I'd appreciate it. Then I'll try it on mine and if it helps with FTEs then I think we're good to go.

[icentropy]

Well i got my G21SF yesterday but wasn't able to make it out to the range, i did, however, take a look at the extractor and best as i can tell it looks like this is the step that is preventing it from moving farther in to catch 10MM brass. I emailed this pic to KKM to have him verify that this is the right one before i file it off. I hope to hear from him today.