Ive some what gone over this before and thought it was rust. I wiped the inside of the barrel down with break free clp before putting the rifle down for a few months. Checking it over this period there have been no problems, still looked brand new when I looked down it. So iI took it out today and put 10 rounds through it and now it looks like rust spiraling all the way down the inside of the barrel. Will copper fouling look like this?