Frosting in a bore|Winchester Rifles|Forum|Winchester Collector

I think frosting is light corrosion that hasn’t got deep enough to be called pitting yet. My buddies 30-40 high wall has it just about full length of the barrel(#3 round)and it will shoot 2 inch by 4 inch groups at 100 yards with tang sights. It likes to string it’s groups vertically and wants to do it all the time.I don’t know the load but it is with cast bullets.