Herk30, remove the primer punch/neck expander assemble from the die, then start sizing a few cases, if removing the assemble eliminates the problem you have eliminated the die as a problem.
A bench rest builder/reloader was having problems with the neck expansion when cases were fired, there is little that can be done to reduce the diameter of the chamber neck so we went about working out the problem from the other direction, he has an A2 RCBS press, nothing suspect about the strength of the press, but with Dillon’s lube in the spray can or bottle his A2 was in a strain, then he went to the sizing wax, same thing, the cases had more resistance to being formed than his press had ability to form, I offered to leave and return with with a lube that is not on the list of approved lubes, instead he opted to use new, unfired cases when forming cases for his new creation.
In the perfect world of sizing, cases are new, once fired or annealed, as the case is worked by firing and sizing the ability of the case to resist sizing increases.
I could have measured the amount of the case that did not get formed before it was removed from the press, after forming the cases required full length sizing or sizing to the chamber, again, new or once fired cases are recommended. I furnished the dies and left them with him, the rifles shoot one hole groups, it is not for me to wonder how much better a tight neck will shoot, the .009 thousands neck expansion bothered him.
F. Guffey