Actually,you can tell if it is on a "A"base(MB)case without a chambercast. If it is, the rimrecess will be deeper than normal and the chamber would measure around .518-.520" in front of the rimrecess( which it self usually measures around .595").If someone else owns the rifle, they will be more likely to let you measure the chamber(dial caliper works, with or without hole gage)than take it to make a chambercast.Note, this doesn't ID case length. FWIW you can make satisfactory cases from 45-90 cases.
Mike

Last edited by Der Ami; 02/01/14 04:33 PM.