Glock 21c converting to 10mm questions

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  • peterock

    Sharpshooter
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    23   1   0
    Jun 24, 2008
    510
    59
    Indianapolis
    So I Have a G21c (factory compensated but really more ported) that I purchased a KKM 10mm conversion Barrel for. My question is with guide rod spring weight (currently stock .45 spring at 17lbs) should I plan to use 20lb, 22lb, 24lb, with a steel guide rod? Does the brand of guide rod matter? Would a recoil buffer be beneficial/necessary? Any help would be appreciated from those who have done this before.

    thanks
     

    NHT3

    Grandmaster
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    52   0   0
    RSA is the same but I believe you may have issues with the extractor, ejector and of course the magazine.

    [FONT=&amp]NRA Life Member / [/FONT]Basic Pistol instructor[FONT=&amp] / RSO[/FONT][FONT=&amp] M&P/Glock certified armorer

    [/FONT][FONT=&amp]"Under pressure, you don't rise to the occasion, you sink to the level of your training. That's why we train so hard" [/FONT][FONT=&amp]
    [/FONT][FONT=&amp]Unnamed Navy Seal[/FONT][FONT=&amp]

    [/FONT][FONT=&amp]“Ego is the reason many men do not shoot competition. They don't want to suck in public” .. [/FONT][FONT=&amp]Coach...[/FONT]
     

    peterock

    Sharpshooter
    Rating - 95.8%
    23   1   0
    Jun 24, 2008
    510
    59
    Indianapolis
    RSA is the same but I believe you may have issues with the extractor, ejector and of course the magazine.

    [FONT=&amp]NRA Life Member / [/FONT]Basic Pistol instructor[FONT=&amp] / RSO[/FONT][FONT=&amp] M&P/Glock certified armorer

    [/FONT][FONT=&amp]"Under pressure, you don't rise to the occasion, you sink to the level of your training. That's why we train so hard" [/FONT][FONT=&amp]
    [/FONT][FONT=&amp]Unnamed Navy Seal[/FONT][FONT=&amp]

    [/FONT][FONT=&amp]“Ego is the reason many men do not shoot competition. They don't want to suck in public” .. [/FONT][FONT=&amp]Coach...[/FONT]


    I do have G20 mags for the conversion but apparently the G20 slide is heavier then the G21 slide so many switch to a heavier spring to compensate, just not sure how much is needed. The ejector seems to be 70/30 with most saying the .45 extractor is enough and the minority switching to a G20 extractor. Figured I would try it out and swap the extractor when I swap calibers, it’s a quick job after all.
     

    NHT3

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    52   0   0
    I'm don't have any personal experience with a 45/10mm swap but I know that going from 40 to 9 goes very smoothly for some while others suffer with reliability issues. My personal feeling is that I would never use something that's been converted for defending myself. I have a 23 converted to 9 that has run flawlessly but it's dedicated for use with a can so it doesn't get a lot of use. The 45/10 conversion is probably more likely to have issues than the 23/9 but I'm sure with a little tinkering you can get it to do the job.
     

    openwell

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    Mar 31, 2014
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    Carmel
    I have converted my G30 gen 4 with stormlake 10mm conversion.
    Had to file down extractor "button" about 0.005 inch
    Now can shoot 45acp and 10mm without any worry.
    You will want to spend the money to get Wolffe springs with several springs.
    They sell pakage with 2 piece guide rod with 3 spring weights for gen 4.
    Because 10mm ammo is everything from Sig 180 gr. plinking to Underwood hot loads you will need multiple springs.
    I reload for my 10mm using Missouri 140gr cast bullets & 5 gr. titegroup for fun plinking.
    You need G20 mags of course.
    Try watching youtube video. I think it is Mrguns&gear . google conversion G21 to 10mm. He explains the extractor modification well.
    BTW I shoot my G30 with 45acp because I have a lot of ammo.
    10mm is fun & mags will give you 15 rds.
     

    openwell

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    also,
    my G30 runs great with 45acp or 10mm
    I would trust it to function every time. and I trust my life on it.
    It's a Glock
    and I have shot it with both enough to know.
    The springs just help you find your fired brass & allow you to shoot super hot heavy cast bullet rounds for hunting or bear defense.

    I think I use the 20# spring which allows me to shoot 45acp & 10mm
    target. plinking. & most defense stuff without changing springs.
    just change barrels & mags & shoot.
     

    peterock

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    23   1   0
    Jun 24, 2008
    510
    59
    Indianapolis
    also,
    my G30 runs great with 45acp or 10mm
    I would trust it to function every time. and I trust my life on it.
    It's a Glock
    and I have shot it with both enough to know.
    The springs just help you find your fired brass & allow you to shoot super hot heavy cast bullet rounds for hunting or bear defense.

    I think I use the 20# spring which allows me to shoot 45acp & 10mm
    target. plinking. & most defense stuff without changing springs.
    just change barrels & mags & shoot.


    perfect, thank you. I’m planning on this being a fun gun that may see some woods carry from time to time. Probably shoot some bowling pins with it at some point. I’ll check out the extractor modification but just ordered a guide rod that comes with 20,22 and 24lb springs.

    what’s the general thought surrounding Recoil Buffers?
     

    openwell

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    perfect, thank you. IÂ’ll check out the extractor modification but just ordered a guide rod that comes with 20,22 and 24lb springs.

    whatÂ’s the general thought surrounding Recoil Buffers?

    don't have any thoughts on recoil buffers.

    very important to do the extractor.
    watched mrgunsngear youtube convert g21 to 10mm and he refers you to kkm website on how to extractor. since kkm no longer offers the 10mm conv. barrel no longer explain extractor modification.
    I will try to here.

    look for youtube vid by bruce huang on g17 gen 4 for disassembly. best on how to by far.

    remove the extractor.
    on the side of extractor that faces the barrel you will find a small circle "button" about 1/32 " in depth.

    you need to take a file an remove about 0.005 " about thickness of credit card.

    why? that button allows the extractor to grab the brass of the fat .45acp case "as is"

    because 10mm is thinner the extractor has to swing deeper toward the barrel to grab 10mm rim.

    after you remove 0.005" the extractor will grab deeper on 45acp
    and just enough on the 10mm

    you have made a simple fix that works on both cases.

    glock will not sell you the g21 extractor
    but other like glockmeister will.
    they are about $14
    so you can buy an extra and keep as original g21 extractor if you want have stock again. but Not necessary.
    also. allows you to try again if remove too much of the "button" on your first try.

    I had no problem. mine works perfect.

    hope this helps
     
    Last edited:

    openwell

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    that extractor "button" works just like a door stop in your home.
    it is usually attached to the wall to limit how far a door swings open.

    but it could be mounted on the door.

    on your glock that button is like mounted on the door.

    if you shorten the stop the door can swing farther.

    by removing 0.005 " you shorten the stop and allow the extractor to swing deeper to reach the 10mm rim and
    while deeper on 45acp by 0.005" functions fine.
     

    peterock

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    Jun 24, 2008
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    Indianapolis
    that extractor "button" works just like a door stop in your home.
    it is usually attached to the wall to limit how far a door swings open.

    but it could be mounted on the door.

    on your glock that button is like mounted on the door.

    if you shorten the stop the door can swing farther.

    by removing 0.005 " you shorten the stop and allow the extractor to swing deeper to reach the 10mm rim and
    while deeper on 45acp by 0.005" functions fine.



    85EBE379-B433-4B43-9023-0C5FF83AF774.jpg

    is this the “button” that needs to be filed? Tip of the file is pointing to it
     

    openwell

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    don't be afraid to file down 0.005"
    with small triangle file.
    I did not need a vice or anything to hold the extractor.
    I used a file I use to sharpen old style Zwickey broadheads for my arrows.

    To understand the theory will give you confidence.

    first. put extractor back in slide but
    do not put plunger & spring or cover plate. just push down the firing pin safety plunger insert the extractor and see how the extractor pivots without any spring tension.

    2nd.
    look at small rectangular area on my extractor pictures to see the small area you need to file down.

    3rd now visualize that by removing 0.005 " patch of metal in that rectangle area nearest the hook claw of extractor will allow it to swing closer to the center-line of the barrel.
    (just do not file the end claw hook tip of the extractor) look again at the flie marks on my extractor and visualize the results you seek.

    you need that because the 10mm cartridge is smaller diameter than the .45 acp.

    your modified extractor will now swing deeper on your .45 acp and just enough on 10mm.

    Mine is very reliable with 10mm or 45acp with my 20# recoil spring.

    you can even try it with an spent 10mm cartridge. place in barrel then rack slide to see 10mm ejects ok.

    finally.
    I did this on my g30 5 years ago so that is why I did not remember the shape was rectangular until I removed it to post pictures.

    You can always buy $14 OEM extractor from glockmeister or other glock parts vendor
     
    Last edited:
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