Glad you found the problem. I had a similar mark appearing on Kragicon cases, but I know it was my doing. After I got my Krag I also got a good deal on a 30-40 Improved reamer. I was going to ream the chamber out, put the reamer in as far as it would go with its larger shoulder and lightly turned it with my fingers. Then I thought, wait, I better read the CMPicon rules. Krags have to be in their original chambering. Operation canceled, but it did leave a mark like yours. I've reloaded the cases many times without any problem.
Information
Warning: This is a relatively older thread
This discussion is older than 360 days. Some information contained in it may no longer be current.