US Patent 9618284 Motor control for externally-operated weapon

An externally-operated weapon has a direct current servo motor that provides motive force to drive the weapon operating group at an average rate of fire. Within a single cycle, the weapon operating group is driven at rates greater than and less than the average rate of fire, while the overall rate for a single cycle is maintained at the average rate of fire. Some benefits of servo motor control include reduced power consumption, increased bolt dwell time, expansion of the weapon's battlefield role from one to many roles, and increased accuracy and shot-to-shot precision while firing from an open bolt position.