I was a tank commander on an M48A3 tank in Vietnam. As part of the OEM equipment, every tank had 2 M-3A1 SMG’s on board. It was VERY controllable on full auto. (due to the slow cyclic rate of 450 rpm) I could easily keep a 30 round burst on a man sized target at 50 yards. The thing would shoot after dropping it in mud, scooping out the excess mud with your little finger from the chamber so a round could enter, (it fired from the open bolt) and the mud would be ejected along with the empty casings as it fired.
As of at least the mid-90's, M3's were still BII on M88 recovery vehicles.
