Not sure about the length issues; but in terms of neck tension, I would seat a bullet in the cases where you don't feel the expander ball dragging on the up stroke - see if the bullets seat with some tension. After seating in the case, can you put the tip of the bullet against the edge of a wooden table and push the bullet in any deeper with just your thumbs? This is kind of a field test for adequate neck tension. And once the bullet is seated, what is the difference in outside neck diameter between the cases that had resistance on the expander ball and those that didn't?