Quite a few made it to Vietnam. An NCO in my outfit had one. A lot of old-timers preferred M3's, Thompsons, and M-14's to the M-16. Reason being that the bigger, slower moving 45acp and heavier 7.62 rounds would cut down the underbrush Mr. Charles liked to hide behind. The faster moving 5.56 would just go thru it. Trouble was, most unit armorers didn't have the parts or knowledge to fix a sub gun if it broke.