A pneumatic assembly for a paintball gun preferably includes a bolt slidable between an open and a closed position. The bolt preferably provides a firing mechanism for the paintball gun by permitting compressed gas to flow through the bolt to fire the paintball gun when the bolt is closed but preventing the transfer of compressed gas through the bolt when the bolt is open. This can be accomplished, for instance, by arranging a sealing member in communication with a surface of the bolt. A port is also preferably arranged through a lateral sidewall of the bolt at a predetermined location. The bolt preferably slides in relation to the sealing member such that when the bolt is open, the sealing member prevents compressed gas from flowing into the forward end of the bolt, but when the bolt is closed, compressed gas is permitted to flow into the forward end of the bolt to launch a paintball. The bolt is preferably controlled by using a control valve such as a three-way solenoid valve to operate a pneumatic piston. The piston can include a larger surface area on one end of the piston to selectively receive a supply of compressed gas from the solenoid valve and a smaller surface area receiving a constant supply of compressed gas. A single supply port in the pneumatic cylinder can be used to supply compressed gas to both the pneumatic piston and the compressed gas storage chamber. A supply of compressed gas to the compressed gas storage area can be cut off during firing to improve gas efficiency.