COLT !! Except for the FN, Colt is the only Department of Defense inspected manufacture. I don't mean a small department like DEA which doesn't have the the same rigorous inspections as our Department of Defense. The first one I was issued had the "happy switch". As long as you took care of and clean it properly, it wouldn't miss a lick. Uhhhhhhh????, that was, ummmm, 44 years ago. I've had my Colt M4 Match Target AR for quite a few years, replacing the Bushmaster.
Oh, that's me with my Colt M16A1 at a forward NDP some where in the land of the big rice paddies.