US Patent 7997260 Paintball marker

A pneumatic paintball marker has, for example, a sleeve that controls the passage of air through the longitudinal barrel or opening within the marker. By sequentially filling separate chambers defined within the opening and the sleeve, the sleeve is able to translate axially through the opening in a sequential manner. When the sleeve is in a forward position, air is caused to be released through the barrel, propelling the paintball. A sear member engages the sleeve and prevents it from inadvertently moving to a forward position. Air filling the chambers returns the sleeve to the loading position.