An apparatus for launching a projectile, such as a paintball. The apparatus includes a body defining a combustion chamber and a bore. A front bolt is provided that moves between a first position and a second position in which at least a portion of the front bolt is disposed within the combustion chamber in the first position. A rear bolt is movable between a third position and a fourth position such that at least a portion of the rear bolt is disposed within the combustion chamber in the fourth position. A drive mechanism is provided to urge the rear bolt to the fourth position. The apparatus includes an igniter device adapted to ignite a combustible mixture within the combustion chamber to propel the projectile through the bore. A portion of the rear bolt is configured to actuate the igniter device when the rear bolt moves to the fourth position. Typically, the igniter device includes a plunger and a portion of the rear bolt axially moves the plunger when the rear bolt moves from the third position to the fourth position.