When looking at the proof test of an action you have to keep in mind the head diameter of the shell or cartridge used. The proof may be in P.S.I. but what is the area of the case head, usually much under 1 square inch. Many shotgun actions are well within the safe range for the nitro loads when the proof pressures are checked approprately. This is not to say you do not have to either have the rifle reproofed by a proof house or by proofing it your self. If you are not sure as to how to do this find some one who does as your life could depend on the rifle passing a reproof!!!