After replacing the o-rings in your AP-2 Gun, it’s important to make sure they are sealing properly. In order to test if the side seals are seating properly and the o-ring is sealing, follow these steps:
With the safety on and the gun disconnected from the hose, hook an air hose onto the gun and pull on the trigger. This pulls the chamber back slightly which cuts the airflow coming out of the tip. The air should cease from blowing out of the tip and should only slightly exhaust at the vent near the handle and the air-motor. If the side seal, the o-ring around the side seal or the oring at the screen screw is not sealing the air will push out of the check valve seat.