I just did 3 20ga barrels this week. I didn't do a before pattern test and still need to take to the pattern boards this weekend, but you can tell a noticable difference in before and after just by looking down the barrel. Worth it in my opinion. 2 of the 20ga barrels had distinct impressions whether it was from where they stamped the wording on the outside of the barrel or welded on the rib. All of those imperfections came out of the inside of the barrel after polishing.