The leak is definitely one of the two orings on the regulator pin assembly, if the leak is out the side hole in the front half of the valve. If your leak occurs when you air up the gun with the trigger pulled, then the oring closest to the back is the one that is bad. If it only leaks when the trigger is released and sear is forward, then the oring closest to the front is the one that is bad.
It is tough getting the orings off and on, but it is possible. Make sure you inspect the area in the valve where they sit. A piece of dirt here will cause your leak. Wash the end of your regulator pin assembly is light oil to flush and dirt away from the underside of the orings. Just because you can't see any dirt on the outer surface of the orings, doesn't mean there isn't any on the inner sealing surface of the oring and pin.
Except for the Automag in front, its usually the man behind the equipment that counts.