An electrical control unit preferably can control operation of a paintball gun having a solenoid valve with an input port that receives compressed gas from a compressed gas supply and an output port connected to a pneumatic mechanism. For instance, the electrical control unit can contain a network of electronic components configured to receive an input signal from a trigger-actuated switch and send a signal to the solenoid valve. The solenoid valve can, for instance, direct compressed gas to and/or from the pneumatic mechanism to operate a bolt or firing valve connected to the pneumatic mechanism in response to the signal from the electrical control unit.