Development of the M75 began in the late 1950s by the Philco-Ford Corporation (later referred to in this time period as Ford Aerospace).

While an aircraft gun pod designated the XM13[2] was developed for it, it would see far greater use as a helicopter weapon, mainly during the Vietnam War.

[4] All phases of the weapon cycle are positively controlled by the drum cam assembly in which a planetary gear train is enclosed, responsible for reducing the motor's high speed to the desired rate for the gun.

The 5⁄8 horsepower (470 W) 28 Volts DC motor is mounted on the turret bracket and drives the drum cam through a flexible shaft in order to isolate it from the weapon's recoil.

The M129 was effectively a redesign of the older weapon to incorporate a concentric cam and improved mount, as well as a higher rate of fire of 400 rpm.