Rob, your last quote nails it. 850 bar remains, to my knowledge, standard CIP proof for 12ga guns--and I believe that's true whether they're 2 1/2" or 2 3/4". Guns designed for American loads, which the Brits consider to be magnum, carry a higher proof. Somewhat confusing, because in their terminology, "magnum" does not mean 3". Your gun has the standard CIP reproof--same that any other 12 submitted for reproof would get, unless someone asked for a magnum reproof.