This subject come up a lot when one has a barrel that is over indexed. Most of the time, the answer is to roll the shoulder of the barrel which expands it's length some. This is also known as swaging the shoulder. Military manuals show a tool made for this which is used in a lathe to turn the shoulder. I haven't found one of these tools and many folks don't have a lathe in the first place. This leads to our friends at Harbor Freight where we can find all sorts of interesting, reasonably cheap, Chinese made tools. I didn't come up with this originally. Some other smart individual on the forum discovered this some years ago. HF has a tool made to cut pipe. It's a big "C" clamp looking thing similar to a knurling tool. The problem is that it is a pipe cutter, not a swag. The answer to this dilemma is to buy two tools and use one of the roller parts to replace the cutting wheel. Of course this kind of waists one of the tools, but it serves it's purpose and probably doesn't cost any more than some other swaging tools.