A paintball gun system comprises a bolt defining a propellant passageway and a gun body defining the following elements: a receptacle for receiving the bolt, a firing charge storage chamber adjacent to but separate from the bolt receptacle, a gas inlet port, a first passageway between the storage chamber and the receptacle, a second fixed passageway between the gas inlet and the receptacle. The first passageway communicates with a first flow opening into the receptacle and the second passageway communicates with a second flow opening into the receptacle. The bolt is axially movable between a chargeup position and a firing position. In the chargeup position, the bolt and the body together define a confined flow circuit between the first opening and the storage chamber. In the firing position, the bolt and the body together define a confined flow circuit between the storage chamber and the discharge inlet.