Greg,
Probably the easiest thing is do nothing.
Second easiest for me would be to make a good fitting mandrel, use a Mylar tape on the barrel outside and cold work the bulge down with a polished hammer. The Mylar tape will protect the barrel to the point that blueing is not damaged. Then leave the bore alone or just a light hone at most. The bulge will still be on the area under the ribs but won't be noticeable on the outside. A relatively easy way to address it and make it visually better.
I have used the Mylar tape method to address dents when I didn't want to damage the blueing. It works.
