There is no facility Under CIP rules for older 12 and 10 bores with 3 inch chambers to be reproofed at the original intended service pressures . The old 12 bore 3 inch standard [2& 3/4 magnum equivalent ] is a thing of the past I am not sure about 2 inch guns either . Standardization is all well and good for new guns but the problem seems to be that CIP is run by educated bureaucrats , not gun makers/repaires so they seemed to have missed the point of reproof . Shame .