Abstract: A portable ball pitching machine for projecting a ball uses a combusting gas to drive a piston which compresses air behind a ball and propels the ball through a barrel. A combustible mixture of air and propane are introduced into a combustion chamber, and a ball is loaded against an air exit of a barrel housing. The gas is ignited in the combustion chamber, and the explosion drives a piston through a compression chamber and generates compressed air. The compressed air is directed through the barrel housing to the air exit and the ball, and the ball is propelled from the barrel. The azimuth and elevation position of the barrel are adjustable. The velocity of a projected ball is adjustable by adjusting a regulator which vents to the atmosphere a portion of the compressed air that would otherwise be directed against the ball.