This mobile moving vehicle was sometimes referred to as the Giant Shotgun; the Big Pig; and the Big Thing.

Used exclusively during the Vietnam War, The U.S. Marines found this light armored mobile tracked anti-tank vehicle mounted with six M40 106mm guns to be quite effective against enemy infantry. This vehicle had limited production and when the Marines decided to stop using them some were turned over to the Army Light Infantry Brigade for fixed bunker fortifications. There was a variation called the M50A1.