I just recently traded for a new Savage axis, it had never been shot. I cleaned it before shooting it and took it out and fired 10 total rounds to get scope set where I want it. I am using Fiocchi shooting dynamics 165 grain soft point. I have a spot just down the side of one rifling from the muzzle to about an inch or so down in the barrel. It's not as wide as the rifling and a short strip of it that has a redish brown color. What could this be?, I put a brush through it about 10 strokes and it didn't change it. Thanks for any help