I have a rem700 VSSF in .308 that I have only neck sized my cases for. I recently learned that maybe I should be FL sizing and bumping the necks back about .002. I have an RCBS headspace and COTL guage which I only bought to vary the COTL. At any rate, I measured about 10 used cases and they measure -.001 on the scale (yes, .001 less than zero). After I did a FL sizing in which I ran my Redding FL die all the way down to the shell holder, I measured +.001 on the headspace guage which indicates that the case actually grew upon re-sizing ( I verified this with several cases). How can this be?