Case lubricant is your friend.
I learned the hard way that if a case goes into a sizing die "hard" it will be even harder to remove, that's when the rim pulls off.
Lots of good case lube and if it starts going into the die hard...Stop....back it out and relube with STP , try again , it might take three partial sizes to get to a complete full length size but STP oil treatment , greasy as all get out , is an excellent case lube for the hard ones .