blume357 said:
I'm skeptical of this problem with cycling ammo... but let's assume it is real:
I have seen it for myself. After a couple months of cycling the top round about once a week, I noticed the round looked shorter. I got out the calipers and measured it. It was 35 thousandths shorter than the untouched rounds. Just to make sure it wasn't a fluke, I rotated the top round out, and kept track of the COAL of the new one. It started shrinking. I now rotate them out periodically.
I'm sure the amount they shrink per cycle depends on the individual round, how it is crimped, the geometry of the feed ramp in the gun it is cycled through, and probably even the procedure used by the owner when cycling. Some may shrink just a little, or none at all, and others may shrink a whole lot more. I know mine do shrink.
As to whether bullet setback itself is a problem, that is pretty well established. Reduced case capacity is very well recognized as a major factor in increased pressure when firing.