When I was in in '74 to '77, I knew some guys that were SF over there in the early 1960s. One senior Sgt. actually preferred his M2 Carbine over the early AR15 (probably a 601 or 602) he had been issued. He said he carried more ammo for the weight, it was more tolerant of bad conditions, and he too said it alway went bang. He said they were always fighting Charlie up close, so it had plenty of power. My dad used an M1carbine on Iwo Jima the night of the big Bonzai charge when their compound was nearly over run. He only said "It never let me down".