Thanks for responding guys. My first inclination was that the area above the belt was what was causing the interference, but as stated above, when I marked it up with a Sharpie, there's no sign of contact at all. If I measure with calipers just above the belt, there is a difference of 0.005" between New unfired cases and mine. These brass had several reloading on them and have grown increasingly tighter. Primers show normal pressure and pockets are still tight. All loads have been under max data by at least 1.0gr or in many instances more.
Might just be time to cycle the grass out but I'd like to know why. I plan to blue up the entire case and look closer.
