Abstract: The present invention relates to a regenerative hydraulic starter/speed regulator system for providing initial rotation and acceleration of a rotatable barrel cluster of a gun gas driven Gatling gun, and for controlling the speed of the barrel cluster during the firing of the gun. The hydraulic system includes a high pressure accumulator for containing a supply of pressurized hydraulic fluid. A hydraulic motor/pump unit is connected to either drive or be driven by the barrel cluster, depending on whether the motor/pump unit is operated in either the motoring or pumping mode. Initially, a servo mechanism operates the motor/pump unit in the motoring mode wherein pressurized fluid from the accumulator is supplied to the motor/pump unit to initially rotate and accelerate the barrel cluster in a firing direction until the rotation of the barrel cluster is sustained by the gun gas drive unit.