Glock 21 Converting 21.4 to run 10MM

Discussion in 'General Glocking' started by bostinks, Apr 2, 2020.

  1. bostinks

    bostinks

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    What parts/manufacturers did you use to run 10mm in your G21.4?
    Basically want just a range toy but possibility of woods gun.
     
  2. mic214

    mic214

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    Several years ago I was given a Storm Lake conversion barrel for my Gen4 G21. All I did was get a couple of G20 mags and swap out the standard RSA for one that was a 20#. So far it has functioned fine.

    I have heard that some folks swap out the extractor , but I didn’t have to do that with mine…

    [​IMG]

    [​IMG]
     

  3. Gokyo

    Gokyo

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    A barrel and a magazine.

    Maybe a recoil spring.
     
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  4. bostinks

    bostinks

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    Nobody seems to have the Storm Lake in stock.
    Lone Wolf doesn't have that conversion, only for the G41 which they told me won't work.
    Can't I just put a Glock G20 barrel in it?
     
  5. Mike-M

    Mike-M

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    Forum member @GRT45 is the authority on all things Glock and 45ACP.
     
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  6. Longbow

    Longbow Millennium Member

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    Can you do that the other way around?
     
  7. norcalAF

    norcalAF

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    Range toy sure, woods gun and risk being eaten by an animal because of malfunction, no thanks. I would just pick up a blue label G20 for peace of mind, once you factor in cost of mags/RSA/conversion barrel you are over halfway to a new gun. Brown bag your lunch for a month and it's new gun time.

    I know, I know, I'm an enabler!
     
  8. norcalAF

    norcalAF

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    I don't believe so, the breechface is smaller on the 10mm.
     
  9. norcalAF

    norcalAF

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    Removed
     
    Last edited: Apr 4, 2020
  10. GRT45

    GRT45 Transform & Win

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    An aftermarket G20 replacement barrel and G20 conversion barrels will fit and function safely in the G21 slide with no loss of accuracy. The video posted above by UpToNoGood is one example of this approach and there are other success stories (GT member happie2shoot is someone that has extensive experience in converting the G21 to other calibers).

    The same holds true for a G29 replacement barrel and G29 conversion barrels in the Gen3 G30SF or G30 Gen4 slides (won't work in the G30S slide). I shoot 10mm, 40S&W, 357SIG and 9x25Dillon with my G30 Gen4 using an extended length G29 10mm replacement barrel (4.6") and G29 conversion barrels in stock lengths. You can expect the same versatility with the G21 conversion and even add 9mm to the list.

    Take a look at the two-part post at Converting the Glock 21 to 10mm Caliber - Part I for the expected accuracy, issues that may come up in the conversion and your options.
     
    Last edited: Apr 4, 2020
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  11. Borg Warner

    Borg Warner

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    If you want 100% reliability, get a complete 10mm slide and barrel for your G21.

    The problem is the extractors. The 10mm and the 45 ACP have two different Case head/Rim sizes. Iether you have to switch extractors every time you switch barrels, or you have to modify one of the extractors to work with both and that's a little tricky.

    I wish someone would make a reliable drop-in converted extractor but nobody does. The problem with the case head/rim differences is worse with the 10mm/45 conversions than with the 9mm.40 conversions and the best way to go is with a complete 10mm upper for the 45 or a 45 upper for the ten.
     
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  12. Longbow

    Longbow Millennium Member

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    Oh, okay. A whole separate top end then and mags?
     
  13. Dribear

    Dribear

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    For 100% reliability, use g20 mags. I have used my 21 mags with my 20 just fine.
    And, if you decide you want to run .40, whether in 10mm barrel or conversion you can use the g20 mags.
     
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  14. winn0040

    winn0040

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    I dropped a Lone Wolf barrel into my Gen 4 21 and was having ejection issues. I have since modified the stock extractor to see if that doesn’t help, but the modification still does not hold a spent 10mm casing tight against the breech face so I’m not sure if it will improve ejection or not. Once this quarantine thing runs its course I will hopefully be able to report back on how the gun cycles Magtech target ammo.
     
  15. GRT45

    GRT45 Transform & Win

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    I've reconsidered the wisdom of including the dummy round retention test in the instructions for making the modification to the stock 45 extractor recommended by KKM. There are too many variables in the stacked tolerances between G21 pistols and conditions of the dummy round an owner may use in testing to rely on the retention criterion.

    I think it's better to rely solely on the other criterion of removing no more than 0.020 inch from the extractor fitting pad measured with a good digital caliper. My most recent two-part post about converting the G21 to 10mm has been edited accordingly. I think you'll be all right with your modified extractor and 45ACP, but I hope you modified a spare 45 extractor as recommended. If it doesn't improve ejection reliability of 10mm, I suggest trying a different brand of 10mm ammo to eliminate that as a possible cause of the problem.
     
    Last edited: Apr 7, 2020
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  16. winn0040

    winn0040

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    Where does the .020 number come from? I have a good digital calipers, but didn't measure before and after, rather just removed material a little at a time trying to get the extractor to hold a 10mm shell casing tight to the breech face. I undoubtedly took more material off than recommended, but I also have two brand new spare extractors that can be put into use as needed. Thanks, GRT45, for all of your guidance with the conversion process.
     
  17. Borg Warner

    Borg Warner

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    Yes.
     
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  18. GRT45

    GRT45 Transform & Win

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    As I recall, the max 0.020 inch spec for material removed from the extractor fitting pad came from an individual who collaborated with KKM several years ago to develop a 10mm conversion method for the G21. I don't recall the guy's forum name, but I remember reading his posts in another forum on the topic. At that time, KKM agreed to manufacture a 45-10mm conversion barrel (now discontinued) and they adopted the extractor modification as their recommended approach. The original founder of KKM Precision that was involved in the project, Kevin McIntire, was killed in a motorcycle accident in 2015, but family members that run KKM now might know more details about the origin of this spec.
     
    Last edited: Apr 7, 2020
  19. winn0040

    winn0040

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    So I was able to take both Gen 4 21s out today and first tried the 10mm conversion set up with modified extractor and still had issues with FTE. Dropped the 10mm barrel in the other completely stock gun and it ran without a hiccup until I ran out of ammo. I will give it another whirl when I replenish the Magtech and Seller & Belliot to make sure it will chew through more range ammo.

    Both guns have very suspect ejection regardless of what caliber is run through them with some rounds hitting me in the head and others flying over either shoulder.
     
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