Abstract: In the embodiment shown, the device comprises a pair of turbine wheels, rotatively journaled, each having a peripheral, concave channel. The wheels are journaled to close onto each other, in close proximity, to define of their channels a circular aperture. A conduit is directed to impel rounds of shot into the aperture, so that rotary torque power will be derived from the turbine wheels. A supply of pressured steam accelerates the rounds through the conduit to the aperture, and a feed wheel singly and successively introduces the shot into the conduit. A drive belt fixed around a hub on the feed wheel and a hub on one of the turbine wheels imparts rotation to the feed wheel, and the spent-missile end of the conduit opens onto the feed wheel to cause the latter to store and advance shot.