The reason case headspace gets longer sfter sizing is the die's a bit too high and the shoulder's pushed up as the body's squeezed down.
Loosen the lock ring on the die then screw it clockwise about 1/16th of a turn. Tighten the lock ring. This sets the die lower so when the press top springs up during sizing, it'll be lower and set the fired case shoulder back more. More die adjustment may be needed.
Last edited by Bart B.; November 21, 2012 at 10:02 PM.