The US M42 Self-Propelled Anti-Aircraft Gun system had been in service with the US since the 1950’s and consisted of a pair of 40mm main guns. This has a lesser chance of hitting a target compared to the number of rounds a 37mm T250 six-barrel Gatling gun could do.
The US Vigilante SPAAG Prototype was a T250 system mounted on a lengthened M113 APC. In the early 1960s, the Army decided that gun-based systems were outdated, and cancelled further development of the Vigilante in favour of the MIM-46 Mauler missile system that also failed to enter service.