factors; this type of ball detent must be sized correctly to avoid compressing the paintball too much, causing it to burst. If too large of a sizer is selected, balls may roll through it. The cartridge and elastic rubber protrusion type detents are primarily used for open bolt markers, or on closed bolt markers to prevent double feeding (feeding more than one ball when the bolt is open for loading). Closed bolt markers generally use the constriction method to prevent "roll outs", a malfunction where the ball completely rolls out of the barrel, causing no paintball to be fired when the trigger is pulled. A partial roll out is when the ball rolls partially through the barrel, causing reduced velocity. Mechanical engineering