My 405 Win dies may have this issue also. I set my dies to just touch the shoulder on bottle neck cases and on the straight rimed case I set the sizer die so a fired case droped into the chamber freely, not touching the chamber wall. A .414 bullet in the case drags a little when droped into the chamber, so I use .413 bullets for the .4125 groove barrel. Back the sizeing die 5 turns off the shell holder to size my cases. My Grandsons have this rifle in Oregon to hunt this fall, when sizing cases to my suggestion, they back the die completely out of a RCBS Jr press I bought in 1964. I had them set the die 3 turns into the press and go with that.
Carpedien, I would guess if I had my dies here to check I may have a the same condictions as you. I am shooting lead bullets so made an expander plug .4115 to get about .001 under size for case mouth. That is how I try not to over work my brass.
Sparky