.45 to 9mm conversion glock 21

Discussion in 'Technical Questions & Information' started by focusmaniaczx3, Jan 10, 2011.

  1. focusmaniaczx3

    focusmaniaczx3 Member

    Nov 16, 2009
    Hickory, NC
    I just purchased a Glock 21 chambered in .45 and it is my understanding that I can basically chamber the gun in anything between 22LR and .45 by simply changing magazine, and barrel, with the exception of .22LR in which case I would also need to change the slide and spring. Now that I know all of this I just need to figure out where to get the parts... I suck horribly at tracking things down on the internet and Google does not seem to be in a very helpful mood tonight. I only have 3 calibers that I am interested in with this gun. 9mm for plinking or for when my girlfriend needs to have the gun for any reason. 357 sig just because I have never used that caliber and i have an extra space for a couple hundred more rounds in my gun safe for a different caliber and then obviously .45 for me whenever I am keeping the gun for myself.

    for the 9mm conversion i would LOVE to lay my hands on a threaded barrel that will accept a compensator. They really help keep you on target and reduce muzzle climb. i must have it for plinking purposes! Once again I have no idea where I might locate any of these conversions.

    Sorry for such a long-winded book for such a simple question. Where could I find these conversions for a glock 21? 9mm threaded barrel that will accept a thread on muzzle compensator/brake (and maybe a glock 18 type 33 round mag), and a 357 sig regular barrel or ported barrel if I am lucky. I am not sure if the spring needs to be changed with these conversions either. Please let me know. I just want to locate everything I would need to put 9mm and 357sig down range with the same handgun.
  2. rocklinskier

    rocklinskier New Member

    Aug 16, 2009
    I'm a little out of touch with the particulars. I am pretty sure that you can convert your .45 to 357 sig by only changing barrel. However, (not for sure) I don't think you can convert to 9mm without changing over the entire upper. Not even sure it that's an option.

    I do know that a G22 (.40 S&W) can be converted to 9mm by barrel change only.

    Below are a couple of places that deal those conversion parts, there are others as well.





  3. BillM

    BillM Active Member

    Jan 16, 2010
    Amity Orygun
    Who told you that you could convert a G21 to "anything between a 22LR
    and 45 ACP"????

    I've never seen a conversion for the G21 to 357 sig, 40 S&W or 9mm.

    I have seen conversion barrels for 40 S&W to 357 Sig and 9mm, all for the medium
    frame. Your G21 is a LARGE frame gun.

    The 357 Sig conversion works fine. Basically it's the 40 necked down, so the cartridge head is the same size.

    The 9mm conversions work. Most of the time. The 40 breechface is
    wider than the 9mm breechface. Even with a 9mm extractor some guns
    are not 100% reliable.
  4. focusmaniaczx3

    focusmaniaczx3 Member

    Nov 16, 2009
    Hickory, NC
    the guy that runs the local shooting range told me that and showed me. i know a .45 G21 can be converted to 9mm because i sat there and told him he was crazy so he pulled one from the "rental pile" and took it on range with 1 loaded .45 clip 1 loaded 9mm clip and a 9mm barrel. fired the .45 clip, tore the gun down, changed barrels, loaded the 9mm clip and fired them all in less than a minute with no jams or problems with extractions. i would go back up there and ask him but he moved to kentucky and i have no way to track him down. i know for sure it was a G21 full frame. that is why i specifically tracked down mine. lone wolf makes a .22LR conversion for the G21 for about $250 which includes 1 10 round mag and a new upper. im not interested in this conversion though. i know this conversion is out there because i saw it with my own eyes. surely somebody knows where i can get it.
  5. muddober

    muddober Active Member

    Sep 19, 2008
    Carson City Nevada
    With all due respect no body takes the barrel off any 45 automatic and replaces it with a 9mm barrel and then shoots it without changing the slide as well. Then the next thing the 9mm Glock magazine is not big enough to fit in the big frame Glock mag well and the 45 mag will not feed 9mm.

    Is it possible they serve alcohol at the range you were at? :D

  6. focusmaniaczx3

    focusmaniaczx3 Member

    Nov 16, 2009
    Hickory, NC
    haha that probably wouldnt be a very good idea! i know what i saw him do and i remember the 9mm being a bull barrel, not that it makes much difference. i guess i must have been mistaken as to which model glock he had. perhaps it was a medium frame? but then which model glock can be chambered in .45 and 9mm? because i know for sure that those were the 2 calibers that he fired through the gun without changing the slide. i have accepted at this point that it was not a G21. so with that settled, what could the gun have been?
    Last edited: Jan 11, 2011
  7. Boris

    Boris Former Guest

    Oct 1, 2010
    I know for a fact I can put a factory Glock G17 slide on my G37. The only thing I see that might cause a problem is the ejector on the G37 is very different from the G17. You could put the proper part in the frame and the G37 would would work fine with a G17 slide on it. It might even work good enough with the G37 ejector. Never tried it. I just mounted the slide and left it at that.

    A G37 is the only 45 Glock I know of that will take a 9mm Glock slide. Hope that helps a bit..........
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