Picked up a Colt M4 .22 rimfire when they first came out, great for practice when the real thing is impractical (my back yard range). Was using a Kimber .22 conversion kit, but bought a GSG .22 1911 copy, and have been using it a lot as well. Except for recoil, you would think you were shooting a .45. By the way, there is a new gun out, copy of a Glock, only in rimfire. Not sure who makes it, but the one I played with recently seemed well made, and was not that much $$
Larry