I think that the simple truth is that cleaning methods have to reflect the powder being used, and because 133 is so clean, we have gotten used to the amount of cleaning that it requires, and may have a problem if we don't adjust for a different powder. I remember when I used to read that Tony Boyer used Iosso on a nylon brush, in the first few inches at the back of the barrel, every time that he cleaned, to prevent carbon problems. At the time, I wondered what that was all about, since my barrels (shot exclusively with 133) all passed bore scope inspections only cleaning with BBS, patches, and bronze brushes. Later, I had a chance to try some of the old 8208 and figured out why he was using the Iosso. It was a lot dirtier than the 133...a lot. At the time that I had read about his use of Iosso, I believe that he was still shooting T. I should add that if a powder produces superior results on the target, I think that it is worth some extra effort cleaning. Evidently that was his thought as well.