A pneumatic paintball gun preferably includes a body and a grip. The body preferably holds a pneumatic housing that contains the primary operating components of the paintball gun. The pneumatic housing preferably includes a pneumatic piston and cylinder assembly. The pneumatic piston is preferably coupled to a bolt for controlling movement of the bolt based on the supply and venting of compressed gas from the cylinder. Most preferably, a normally-open three way solenoid valve supplies compressed gas to a forward surface area of the piston to hold the bolt in an open position. In the open position, a paintball is permitted to load into a breech area of the paintball gun. In response to a trigger pull, the three-way solenoid valve is preferably configured to vent compressed gas away from the forward piston surface area. Pressure supplied to a rearward piston surface area preferably causes the bolt to close, moving the paintball into a barrel. The bolt is also preferably configured to operate as part of the firing valve, such that closing the bolt causes compressed gas to be released into contact with the paintball arranged in the barrel to launch it from the paintball gun. A paintball detection system can also be provided having a circuit board configured to fit in a recess formed in a breech section of the pneumatic housing.