G20 and G21 barrels will swap easily .... I own both ( gen 3's ) and are interchangeable .
I also have a G40 long slide and the gen 4 barrels will fit a gen 3 slide but not the other way around due to the re-designed dual rate springs found on the gen 4's .. Will a G21 barrel swap into a G20 slide? I don't think it does. Will not. Wish it did, but alas ... That is what I thought. Thanks Rick.
Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats.
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