If you have a new barrel and it is perfectly clean, you will get black patches as long as you keep running that polishing compound in and out. The black is from the steel you are removing. You do not remove very much, but you are taking some out every time you stroke the bore. I have a rifle that I stroked 600-700 times in total, not all at once. It shoots great not with little copper fouling. Stop giving it strokes, when you get the barrel smooth so it does not copper foul quickly. It is different for different barrels. I always cleaned mine thoroughly before polishing, but I know some people use the polish to remove copper fouling. IMHO you should clean first, then polish. I have polished and then went back and done it again, until I get the results I want - no copper fouling. This makes for longer shooting session before accuracy starts to deteriorate. Good Luck and Good Shooting