Originally Posted by
athomas
An on-off pin that is too short will allow the gun to fire, but not reset. Not firing is not a symptom of a pin that is too short.
Not firing is always a symptom of not enough air pressure in the chamber. This can be caused by the velocity not being turned up far enough, excessive bolt stick due to a level 10 carrier that is too tight (not a problem with a level 7 bolt), the trigger rod is too long not allowing the on-off pin to clear the on-off top oring, an on-off pin that is not short enough to clear the top oring when the trigger is forward, or not enough air pressure coming from the tank regulator.