There's a discussion on the G-21 going on on another site. It was brought up that the Glock 21 was derived from the 10mm Glock 20, which uses a much higher pressure cartridge. One fellow described the G-21 as "the most overbuilt .45 on the market".

Not sure if that's accurate when guns like the HK 45 are brought up, but does anybody have any ideas as to the average longevity of the G-21 when compared to other .45's?