I have a gen4 g21 that I want to put a 10mm barrel in, I don't know how to identify what generation this barrel is.  Can you all help me.  The part number on the lug is 0625


What generations are compatible?


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I'm not a Glock guy, but I suspect the next question is will the breach face and extractor of your G21 work with 10mm ammo. Hopefully someone else will chime in.

I'm not positive if the G-20 actually fits the G-21, you might call and ask KKM or Lone Wolf and ask about the compatibility!
It is my understanding that the barrel for the 10mm G-20 will fit the G-21 but the Barrel hood may be slightly narrow for the G-21?
Many do change the 45ACP extractor to the 10mm extractor. 

Gen2, gen3, and gen4 barrels are compatible with each other. Gen5 barrels may be different. I do not think they make a Gen 5 10mm.

The G20 and g40 barrel will work in a g21. It won't be as good as a G20, but it won't be bad. You probably won't notice a difference. You might need to change the extractor. You shout try with the stock g21 extractor first. I do not recommend this setup for self defense.



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Sorry gents, my google foo was poor this day.  Lone wolf's barrel compatibility was pretty clear, I was just being scary I guess before purchasing the longer barrel for my g21.  They are compatible.  Looks kind of goofy, but should work just fine


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