Hello everyone, I am new here and was hoping to break the ice with a question in regards to some brass. I purchased brand new Hornady Brass for 257 Wby Mag. and proceeded to full length the brass with a brand new RCBS die. I also reamed the neck lightly, but when I was ready to press some Barnes ttsx 100 grain bullets in, some of the brass was collapsing at the shoulder when I pressed. It collapses perfectly straight, not in any angle or anything like that. I am using an Rcbs press with turret, and it seems to be locked in fine. There is no additional movement when pressing. After ruining like 5 brass, I started press with very small movements and spinning brass a 1/4 turn thinking maybe that the ribs from barnes bullet was not seating just perfect and was causing brass to buckle when pressure was applied. I have some Weatherby brass that has been shot only once, going to try that to see if I get same results. Please give me any input if it seems that I am making an amateur mistake. I have reloaded for several years, but been away from it for a couple, things were a little foggy at first, but it's coming back.