I picked up a virtually brand new Gen 4 Glock 21 a week or so ago from a guy who had purchased it hopeful that the adjustable backstraps would make it possible for him to use it, since he has fairly small hands.
Bad luck for him, good luck for me...it didn't work out for him.
So, I got this gem of a Glock in LNIB condition.
I've got an older Gen 3 Glock 21, police trade in and love it, but had to have the Gen 4.
I put it through its paces today with my son. Love the grip and have the largest backstrap on. Again, I have to say, the G21 is my favorite Glock. I find it extremely manageable, the polymer soaks up energy from the .45ACP and provides a very satisfying shooting experience.
Anyway, here's my video of our session with it. We were shooting cheapo Russian ammo, not a single hitch or glitch.
LINK TO VIDEO HERE.