I'm having a hell of a time getting brass for this cartridge. I tried to makedsome out of 308,and I get alot of dings and messed up looking shoulders. What I am looking for is advice on what is the best brass to form from. I know it is bassed on the 30TC cartridge, so would this be the best to form from or should I go with others first IE: 308,243,260. Thanks for any help-Lawrence