 The US Army's first custom-designed anti-aircraft weapon was the M42 Duster, mounting two Bofors 40 mm guns in an optically aimed turret on a M41 Walker Bulldog light tank chassis.First entering production in 1952, the Duster quickly became outdated as aircraft performance increased.To replace the Duster, the Army started work on the Sperry Vigilante, which mounted a powerful 37 mm Gatling gun on top of a modified M113 Armored Personnel Carrier chassis.