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.
"Do not follow where the path leads, rather go where there is no path and leave a trail."