Ron,
I have made half a dozen or so plugs to remove dents with and taken out dozens of dents. There's one plug/rod next to me as I type this. I make them using drillrod because it's a fine grained steel that machines well. I don't harden them. I do round the nose off and polish them a bit, but not all that much. I make them about 2" long and drill a 1/4" dia blind hole in the end opposite the nose. This is for centering a 1/4" rod so I can TIG it on. The rod should be longer than the barrel of course. Grease it up before you drive it under a dent. If you are going to refinish the barrels, you can use a steel hammer that has been polished on the face. If you want to preserve the blueing, some of the guys have been using a thin brass shimstock over the dent area to prevent marring by the hammer face.
If the dents are in the choke tapers, much more finess is required as well as the taper angle and diameters. Might require some good measuring tools and a good machinist.
