Privacy guaranteed - Your email is not shared with anyone.

Welcome to Glock Forum at

Why should YOU join our forums?

  • Reason #1
  • Reason #2
  • Reason #3

Site Description

Glock 21 10mm Conversion (How To) and Review

Discussion in 'General Glocking' started by plouffedaddy, Aug 24, 2012.

  1. plouffedaddy


    Apr 1, 2011
    Seemingly about every week someone posts a question on how to do a 10mm conversion on a G21 or G30 (process is basically the same as below...) here... so I decided to do a little video explaining how to do it and demonstrate the difference in firepower you'll achieve while doing so.​

    Gun---Generation 3 Glock 21SF with 1913 rail
    Parts used for the conversion:
    -KKM 6'' 45-10mm conversion barrel
    -LWD 10mm extractor (KKM recomends modifying a stock 45acp extractor however; more on this in the video below)
    -LWD stainless guide rod with 20lb recoil spring (vs 17lb factory set up)​

    Here's a video that will show how the gun shoots with the standard set up, 10mm conversion setup (with multiple types of ammo), a demonstration showing how to install the conversion parts, and chronograph tests with both setups of the gun showing the power difference with the 6'' KKM barrel.​


    Chrono data for the 45ACP:

    -Federal HST 230gr JHPs: 817fps, 341 ft/lbs
    -Winchester Ranger 230gr JHPs: 896fps, 410 ft/lbs​

    Chrono data for the 10mm:​

    -Underwood 155gr Gold Dot JHPs: 1587fps, 866 ft/lbs energy
    -Blazer 200gr TMJ: 1098fps, 535 ft/lbs energy​
    Last edited: Aug 24, 2012
  2. vaquero aleman

    vaquero aleman "ah-lay-mahn"

    Jan 9, 2009
    The Wild Wild West
    I really wanted to buy the KKM 45 to 10 conversion barrel but it is no longer listed on thier website. But, while I was at the range, with my son, I found a Glock factory 6" G20 barrel for $149 so I decided to test what I had read here at GlockTalk. I put the stock G20 barrel in my G21 with a wolff 20# assy. and first ran some 40S&W through it-had to cycle the slide by hand with the 40. Then I ran some 10mm 180grain through it and, except for the empties stove piping, it shot the 10mm just fine. The fit and function of the stock 6" 10mm barrel in my G21 was as good as the stock G21 barrel. So, as soon as I can do the KKM mod on my extractor I will have a fully functional 6" 10mm Glock 21. And I now know that, with some tweaking, that it will shoot 40S&W using the factory 10mm mags. I would say that for those of us that convert our 21s to fire 10mm, we have at least 6 calibers that we can fire from one gun. My 21 fires .460 Rowland, 45 Super and 45ACP/+p already. And there are several G20 conversion barrels available, so the list grows. IMHO the G21 is the most versatile pistol manufactured.

    Last edited: Dec 25, 2012

  3. F106 Fan

    F106 Fan

    Oct 19, 2011
    Last edited: Dec 24, 2012
  4. samurairabbi

    samurairabbi Dungeon Schmuck

    Dec 31, 1998
    Indianapolis, IN
    "Except for the stove piping" should not be considered a minor exception. The 21 slide/extractor combination is set up for the larger .45 diameter. The slimmer 10mm case is giving that setup trouble. It may be impossible to correct.
  5. vaquero aleman

    vaquero aleman "ah-lay-mahn"

    Jan 9, 2009
    The Wild Wild West
    I have googled both the G20 and G21 extractor and the photos look the same. The KKM fix is, supposedly, to file down the step next to the claw which will allow the extractor to obtain more bite and work properly. I will know in a few days for sure. There are other threads here that claim that installing a G20 extractor in the 21 slide is the best way to go. And if I had the money, I would have preferred to purchase a complete G20 upper for my 21 as the frames are essentially the same.

    Last edited: Dec 24, 2012
  6. elijah58


    Feb 6, 2012
    Aiken, SC

    The simplest way is what I do, I usually go to the LGS and just convert cash to a G20 entire process takes 10 minutes........:supergrin::supergrin:
  7. plouffedaddy


    Apr 1, 2011
    [ame=""]Glock 21 10mm Conversion: Review & How To (HD) - YouTube[/ame]

    Re-uploaded the video on the new channel....
  8. bmoore


    Jan 15, 2006
    Under a regime.
    I like your reviews/videos. I would just buy a G20 upper from Glockmesiter. Actually I just bought a G20!
  9. vaquero aleman

    vaquero aleman "ah-lay-mahn"

    Jan 9, 2009
    The Wild Wild West
    I appreciate your post, and thanks for sharing your knowledge. A few years ago I had a G20SF with a Lone Wolf long slide and Storm Lake barrel, sold it here in the classifieds. I really liked my G20 but now that I've had my G21 for a while, I feel that I like it better.
  10. franco4027


    Oct 14, 2012
    I did the conversion with a stock length storm lake barrel 10mm conversion barrel for the G30 gen3. It was a little tight when I got it but it never failed to function. A box of ammo later it was a smooth as new. Ejection was a little erratic and some shells would go over my head. I did the extractor mod and now it is perfect. The only thing that is unusual is full power shells get thrown 20 ft. Even low power ones go 10 ft. I put 21 lb spring in and I see no difference. 300 rounds no feed or extractor issues. Accuracy is good and recoil is no worse than 45+p. I love it and it makes big noise like a hot 357 mag
  11. picketpin


    Jan 25, 2009
    Bozone MT
    Thanks for posting all your experimentation. Much appreciated!
  12. Grizzz


    Nov 16, 2011
    Ko-Kwill Or.
    I have a g21sf gen3 conv. to 10mm Storm Lake 5.30 barrel. 23# RS & ss guid rod . I have no issues with this setup.
    Gen.3 slides in g21 & g20 have the new updated extractor & don't need replacement. As i said, i have no ftf's or fte. If its a new gun, put some rounds down range & it will get better. Good luck with your conv. :supergrin: