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?
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January 4, 2014, 05:03 PM
First off, 4130 and 4140 differ in carbon content which effects the hardenability of the steel. In the annealed state which your tube probably is, the strength should be similar. Most shotgun barrels are plain carbon steel, not chrome-moly. I have not seen this in print anywhere, learned it by playing with an alloy analyzer.
I would not push my luck by trying smokeless powder in a muzzle loading shotgun, too many variables such as consistent wad pressure that could bite you.
I will do a few stress calculations on your tube and get back with you.
January 4, 2014, 06:41 PM
1/4" wall 4130 will handle any load that you would fire in and shotgun but I think it would be a very heavy barrel for a shotgun.
Really doesn't matter a lot as the use of punt guns way back when have most limited to no larger than 10ga for migratory birds.
January 4, 2014, 10:06 PM
So I am guessing a 1" Id bore is "slightly" larger than 10 gauge ? or Not?