I think you said these were fl resized. It could be that you’re generating too much headspace or short base to shoulder length and the primers are backing out a bit and then being riveted by the case head as it backs up to the breech face. Try backing off on the charge a bit and just neck sizing the cases such that it takes a slight effort to chamber them. The cases and primers from the other mild loads fired on the same day seem to be giving a similar look so neck sizing or partial fl resizing might do it. I had this problem with my second 243 even with starting loads. Look at the primers after depriming a few cases. From the side, if they look like little mushrooms, you may have found your problem.
Velocities are a bit hi but part of that could be barrel length as someone mentioned. Several angles to consider.
