I have one of the earlier mk85s with the Walther barrel. When I was a rookie bp hunter back in the 80s I hunted a week in the rain. When I got home the barrel had rust spots all over it. I quickly discovered birchwood casey sheath. It was great at protecting the barrel from further rust.My brother put a barrel condom on my gun after I got the misfire problem fixed. I noticed the white condom turned orange over the day. I actually formed a rust ring around the end. The bore is in great shape. I found a place in NC that will reblue the gun with a much better finish then it has now.