I have a lovely 36" SEAMLESS 1" inside diameter 4130 steel tube with .250 walls that I am contemplating an awesome shotgun project. I originally was going to build a black powder mini Cannon for some Arial launch burst shells but after seeing beautifully slick the inside is, I thought "what a killer waterfowl shotgun I could build" > Now I know usually all gun barrel steel is nominally supposed to be 4140, but 4130 only has slightly less chrome moly count to it. I am just wondering how much different that might be? I know it would definitely handle Black powder, but what about some smokeless like blue dot or 2400? I heave plenty of wall thickness at .250 which I could taper down from the "chamber" area leaving at least 6- 8 inches heavy wall, and I would have to get creative with making a sealed breech plug, but using the smokeless muzzle-loader idea (as i just built one) - and how hard would steel shot be on 4130 steel?