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Glock interchangeability

Discussion in 'Handguns: Autoloaders' started by Tinman357, Jan 17, 2013.

  1. Tinman357

    Tinman357 Well-Known Member

    I'm asking 'cuz I don't know. Can you change a G20 to a G21 with just an upper change?

    IOW, can I convert my 10mm to fire .45acp I know my G22 will fire. 357sig .40s&w and 9mm with a barrel and mag change.

    Getting the G21 upper and mags arent an issue. Will it work?
  2. Inebriated

    Inebriated Well-Known Member

    You can switch uppers.
  3. G21NE

    G21NE Well-Known Member

    Yep, same frame size.
  4. Tinman357

    Tinman357 Well-Known Member

    Excellent! Thanks.
  5. psyopspec

    psyopspec Well-Known Member

    Are the magazines the same too? I was under the impression that a 10mm cartridge shares the same case diameter (but shorter length) as a .40 SW whereas a .45 ACP is, well, a .45.
  6. Havok7416

    Havok7416 Well-Known Member

    10mm is 10x25mm and .40 S&W is 10x22mm. The .40 is nothing but a shortened 10mm (the 10mm was invented first and the .40 came along later).
  7. psyopspec

    psyopspec Well-Known Member

    Thanks. Follow-up: would a 10mm magazine function with .45 ammo if one were to just swap the slides on their Glock 20 to a Glock 21 upper? Or with the larger .45 cartridges, would they lie too low at the top of the magazine for the slide to effectively move them into the chamber?
  8. Havok7416

    Havok7416 Well-Known Member

    10mm has a smaller diameter than .45 so the feed lips on the magazine would prevent .45 rounds from feeding into the magazine. Bending the feed lips open would cause 10mm rounds to not stay in the magazine (don't do that).
  9. psyopspec

    psyopspec Well-Known Member

    Thanks. So it looks like the answer to the OPs question is that you can change slides between the Glock 20 and 21 no problem, but would need the corresponding magazine to actually use the gun.
  10. Skribs

    Skribs Well-Known Member

  11. powder

    powder member

    The more affordable route: start with the G21, and just get a Storm Lake 10mm conversion barrel.
  12. eldon519

    eldon519 Well-Known Member

    Is the ejector the same between the 20 and 21? I have no idea myself, but I know on the 9mm vs. .40/357 SIG guns, the 9mm ejector bends inward because the 9mm case is smaller. Not sure if the 10mm/.45 situation would be similar.
  13. G21NE

    G21NE Well-Known Member

    Oh yeah, forgot about that, you may need to change ejectors and/or trigger group housing. The 10MM being a smaller diameter case could have the effect of the ejector missing the case altogether, or barely hitting it and causing problems.

    If it were the other way around, converting 10MM to 45ACP, it could cause an unintended discharge if the 10 mm ejector contacts the 45 primer when ejecting a loaded round. OR it may not chamber a round in the first place.
  14. hentown

    hentown Well-Known Member

    Same, exact lowers. Same ejectors, accordingly. Different extractors, making for the 10mm conversion barrels pretty "iffy", as a 10mm extractor won't work in a .45ACP slide.
  15. MassMan

    MassMan Well-Known Member

    Changing from 40 S&W to 357 Sig requires a barrel change but the same mags will work.

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