In a paintball gun in which projectiles are admitted into the breech from a feed port through a radial aperture, sensors positioned in line with the aperture detect whether a projectile is completely or partially inserted into the breech, or totally missing. An electronic logic circuit allows the firing of the gun only when the projectile is fully inserted, and prevents the firing when the projectile is only partially inserted into the breech. A dry firing of the gun is enabled if the breech remains empty of any projectile for a short period. The dry firing is intended to dislodge any projectile jammed in the feed port.