Thanks for all replies. Cases sized to .000 on the RCBS gauge chamber satisfactorily. That will be SAAMI spec and should resolve headspace issue.
Bent rims and high primer warnings duly acknoweldged.
Guffey thanks for your time. I had never heard of using a feeler gauge on the shell holder/die rim but I understand what you are doing.
Slam, not disbelieving, just not completely digesting.