A system is disclosed for extending a recoil impulse of a gun. The system elongates the recoil impulse to spread the recoil energy over time and reduce felt (i.e., peak) recoil force. Although the system adds weight to a gun, the system reduces felt recoil beyond what is possible by simply adding weight to a gun by using an inertial weight on a spring to absorb and release energy. To prevent shaking, the inertial weight system is tuned to a gun so that the inertial weight hits a pair of stops at certain points in the gun's discharge action cycle.