Here’s my latest observation. I was running my expander mandrels through necks that had not been lubed, and had been full length sized in my standard dies, with no expander ball in the dies. This made for quite narrow necks. The expander mandrel would then open up the necks considerably, inducing run out and shortening the case a few thousandths.
I removed my depriming pin in the dies, raised the expander balls to almost touching the neck when the case is fully pressed into the die. This keeps the neck aligned in the die as the expander ball stretches the neck back out. Minimal run out. Then I run the expander mandrel through the neck to uniform neck tension. Much less run out for me with this technique and hardly no case shortening. Also less force needed to expand the necks this way rather than full length resizing with no expander ball. I also deprime with a universal depriming die.
