Sounds like your cartridge brass is work hardened enough that it won't accept resizing is my best guess. Set your resizer die up with a comparator gauge, Then anneal your brass. Trim them to minimum OAL length after their annealing. And run them back thru your resizer die again. See if doing that makes a difference in their chambering. If there base area still hangs up upon the bolts camming action to where its difficult to chamber a complete round. Then you have the possibility of other barrel issues needing to be addressed.
"JUST A OLD DEPLORABLE THAT'S IRREDEMABLE."