Mike knows what he is talking about! I owned a fabulous Purdey .450 3 1/4"BPE top lever, Whitworth barrels. 5 or 6 small rings in each barrel. It was tested by a writer you would all know. Don't know if the rings were caused by him or after but he used smokeless powder with a filler. I also have a friend that ringed an Alex Henry barrel with smokeless loads (damascus barrels). I will not use anything but blackpowder in my old double rifles!