How old is the ammo ? Sounds like the powder may be on the verge of going bad and that can effect the brass as can corrosive priming on pre 1930's ammo. I'd pull them down and deprime then anneal down to just past the shoulder. Also you should buy some of the Graff brass mentioned above while they have it in stock. I have two m14's and a 141 and as a rule they nibble at the rims a bit when they extract the fired case . I clean the nibbles up with a small fine cut file but eventually they get rougher than I want to use. Mine are some of my favorite rifles.
Last edited by EddieSouthgate; 03/19/23.
