I do a weekly wipe down and inspection to avoid any corrosion. This week I just happened to look inside the tip of the barrel and noticed brown color in the groves. The barrel has less than 200 rounds through it and of course with non-corrosive ammunition. I seriously don’t think its rust since there are other parts of the barrel that are missing the coating and the metal is still shiny. Does HP use a coating in their barrels that turns brown? Thanks.