An improved paintball gun uses a pneumatic sear to hold the firing valve closed against the high pressure gas occupying the other side of the valve. In this manner, only one operation is required between depressing the trigger and the firing of the paintball gun because a double-acting cylinder is not required as an interface between the trigger depression and actuation of the valve. The paintball gun is also substantially faster than existing electro-pneumatic paintball guns because it uses a blow forward bolt, in which higher-pressure gas is held directly behind the bolt and has only one direction to travel during the firing of the paintball gun.