Interesting. In this case, I have a way to compare if the brush has indeed scored the shotgun tube bore, since the Browning XT combo has two sets of tubes. The unsingle tube has been used for 6 months, and cleaned after each outing, and the doubles tube(s) is unfired. Careful comparison of the two may answer the question. In the case of the unsingle, that would be 24 weeks of shooting at least, two sessions per week, or 48+ times the bore has seen the stainless brush. It appears the unsingle tube seems to have lost it's mirror finish, which is the reason I asked the question in the first place.
