Scuff marks on base of brass

Marks at the base of a cartridge are the result of the die doing its job, resizing the case. If a chamber is on the large end of the tolerance, the case expands to match it. The sizing die then has to push it back to specification. This rubbing results in that burnished look. Between the space the shell holder takes and the radius at the base of the die, you end up with a line about ¼” up from the base of the cartridge.