I have made a number of .40 caliber rifles using Rice barrels. They have all been ultimately given to my children and grandchildren. I shot all of them, sighting them in before gifting them, except the last one. I usually load with a .395 Hornady swaged lead ball and spit lubricated .016 pillow ticking from TOW. two rifles ago, I changed to a .390 ball, using both a .016 and .020 patch, both with acceptable results. Of course, the thinner patch loaded more easily. No fouling issues with either load. The last rifle, using a .016 patch, .390 ball, it fouled too much to load with reasonable effort after about 3 shots. I cleaned, went to the thicker patch, with no better results. The muzzle is also sharp and cutting the patches, so Daryl's observation regarding factory crowning proves true for this barrel. although I have not noticed an issue on a Rice barrel before. Note: new barrel with no rust.
The next time I travel to my daughter's farm, I will smooth the muzzle, but what gives on the fouling? Same Goex 3fg powder, same Hornady swaged balls, same pillow ticking. How do I fix this? Would scrubbing the barrel with scotchbrite help? If so, what color do I use?