Gentlemen. I have a problem I've never encountered before. Any help/thoughts on the matter will be most appreciated. Below are photos of cases as ejected from a Winchester 70 in 300WM (bought used and just my 2nd time shooting it). All of the spent cartridges have the same scoring. When I noticed it I first checked the remaining charged cartridges thinking maybe my dies were the problem; not so. The cases show no blemishes until shot. It's not affecting accuracy, as it shot a sub 1/2" group. Hopefully the photos show that the scoring is in the shape of a long, narrow S (-------------_______ kind of like this). Any thoughts or experience with this? Thank you in advance for any help, Richard.