A few years ago at a match at Visalia, CA, I had the pleasure of talking with George Kelbly. During that conversation the topic of cleaning came up. He 'lowed as how that BR shooters probably clean a good bit more than they need to and that unless an unusual number of sighters was used that cleaning every two or three matches should be fine. I follow that advice, and I have never see a case where I thought that I was shooting larger groups because of it, in fact my impression many times is that they may be slightly better the second or third group after a through cleaning, I have also noticed that barrels are not all the same in this respect, some shooting at their best after cleaning and a couple of foulers and one in particular that seems to prefer to be dry patched only between matches, to remove the loose powder fouling, which I do, leaving a through cleaning till the change of yardage, or end of the day. I was discussing this point with one of my benchrest betters, Del Bishop, a fine shooter and bullet maker from Washington,state) and he told me that one of the shooters up in their area, who regularly takes home a lot of wood, hardly cleans at all. On the opposite end of the spectrum is the very successful Bart Sauter who staunchly believes in thoroughly cleaning between each and every match.
Getting back to the original topic of this thread, I think that many shooters have bigger cleaning problems than whether they unscrew their brush at the muzzle, like inadequate bore guides, IMHO, TK Nollan, and Chet Whitebread are at the leading edge at the moment.) bowing their rods, working the rod too fast and hard, tight fitting patches,,Why squeeze the solvent off into the chamber before the patch get into the bore?), running the rod too far out of the muzzle during the aforementioned overly vigorous stroking,potential crown wear), and not wiping the rod off often enough to remove the slurry of abrasive particles that it becomes coated with, all seem to me to be more serious problems. A friend has a bore scope and although I use very conventional cleaning techniques, my barrels always pass muster under scope examination, including their crowns. As an aside, I might mention that I have never had a match barrel that gave me problems with copper fouling, although I will admit that the total number of barrels invloved is miniscule compared to many shooters that I know. Now if I could only get better at reading conditions...