An apparatus for generating an impact against a target object comprises a driver reciprocally disposed in a housing. The driver includes a hollow tube having a closed end and a nozzle sealing the other end. A piston is slidably positioned in the tube. Propellant is disposed between the piston and the closed end of the tube and fluid is disposed between the nozzle and the piston. A rupture disc is provided for sealing the nozzle which is adapted to rupture when the pressure in the tube exceeds a predetermined pressure. A striker is also mounted in the housing so that in a retracted position of the striker a head portion is proximate the driver and a portion of a shaft extends outwardly from the housing. The striker member is movable between the retracted position and an extended position. The propellant is ignited so that combustion gases build pressure in the tube between the piston and the closed end of the tube causing the pressure in the tube to exceed the predetermined pressure for rupturing the disc. This causes the piston to move toward the nozzle and fluid to be expelled through the nozzle for moving the driver against the head portion of the striker. The driver transfers energy to the striker for moving the striker to the extended position at high velocity for driving the end of the striker with great force against the target object. Recoil action is cushioned by the fluid exiting the nozzle.