My experience has been the same. The Sierra may have the least fouling of any bullet out there. If you look down your barrel with a Hawkeye bore scope, it will probably show some pitting and other irregularities that are grabbing copper as the bullet goes by. As long as it shoots well, I would just accept the extra cleaning required as part of owning that rifle. Could be worse . . . . . gun cleans very easily, but doesn't group well.