Found this at THR.
August 24, 2010, 12:36 AM
Big Negative on that man, i tryed to install my dads G21 barrel on my G30, seems that the locking lug and the recess where the recoil spring sets is a bit longer on the 21 barrel than the 30. It went on fine, but once the takedown lever got ahold of it, it took me and my dad both to get the slide and barrel back off. My advice...dont try it.
August 24, 2010, 10:39 PM
a g21 barrel will not work with a g30. the locking lugs are different.