A bolt assembly for a paintball gun preferably includes a valve stem having an output port that can supply compressed gas to a compressed gas storage chamber. A bolt is preferably slidably mounted on the valve stem to move between a forward and a rearward position. The bolt can include one or more bolt ports configured to communicate compressed gas from the compressed gas storage chamber to a forward end of the bolt for launching a paintball when the bolt is in the forward position. When the bolt is in a rearward position, the bolt ports preferably communicate compressed gas from the outlet port of the valve stem into the compressed gas storage chamber. A sealing member can be arranged on the valve stem in communication with the bolt to prevent compressed gas in the compressed gas storage chamber from entering a forward bolt chamber when the bolt is in the rearward position and to permit compressed gas to enter the forward bolt chamber through the bolt ports when the bolt is in the forward position. A flow control member is preferably slidably arranged on the valve stem and configured to permit a flow of compressed gas from the valve stem output port into the compressed gas storage chamber when the flow control member is in a first position and to restrict or prevent the flow of compressed gas from the valve stem output port into the compressed gas storage chamber when the flow control member is in a second position.