I have had this problem in the past. It was very frustrating and took a while to figure out. I was using regular dies with an expander ball and having a very hard time pulling the expander ball through the case necks also.
The problem was very hard, thick brass and/or too much neck tension. Hard, thick brass is very hard to resize with an expander ball type die. Most regular dies squeeze the necks down way more than is needed and then force the expander ball to open the neck back up to the desired diameter. Hard, thick brass is very hard to pull an expander ball through and will spring back to a smaller diameter after the expander ball is pulled through.
Annealing will help this as the spring back is greatly reduced because soft brass has very little spring. The force required to pull the expander ball through the neck is also greatly reduced. Seating a bullet in softer brass is also much easier and will reduce the crushed bullet effect.
Neck turning cases with thick necks will also make using an expander ball type die easier. The thick brass is forced to an even smaller diameter in a normal die when the neck is sized and then it is even harder to pull the expander ball through. If you turn the necks down to a reasonable thickness the expander ball will pull through easier.
One of the major die manufacturers explained all this to me after a few phone calls. The dies must be manufactured so that they will size both thin brass and thick brass. Therefore a comprimise is made in how much the necks must be sized down. Thinner brass requires a much smaller diameter neck sizing section in the die. This makes the die compresss thick brass down much more than thin brass and therefore the expander ball is hard to pull through. The die manufacturer did offer to ream the neck sizing section of my die to a larger size to accomodate my brass to solve the problem.
Switching to Redding type S bushing dies solves most of these problems. They allow you to control neck tension by changing the size of the bushing. You don't have to worry about pulling the expander ball anymore.
