I use a dowel more aggressively. I bandsaw a split in one end and insert two back to back strips of emery cloth. I cut them so the can just be inserted into the barrels when rolled around the dowel. I chuck the dowel in an electric drill and run the drill as fast as it will go. You can hone out several thousandths in just a few minutes, and even polish out minor pits in the bore or chamber this way. Use coarse emery to cut and fine emery to polish.