This gauge allows you to compare your
handloads to the size of a fired case.
I start by calibrating my Digital Headspace Gauge by
zeroing it on one of my fired cases. Then I measure my handloads, and the gauge displays the exact chamber clearance for that particular
I have (3) different rifles chambered for .308 Winchester, and each one has a chamber that's slightly
different from the others. I can make my handloads compatable with other rifles, by making them fit the smallest chamber in that caliber.
However, I can also make my handloads to much tighter tolerances (for best accuracy), and build them specifically for each rifle.
Setting the height of your resizing die to "bump your shellholder" will almost always make handloads with too much
chamber clearance. This is usually more serious on belted magnum and rimmed calibers, and it can result in case head separation.
However, neck sizing is not the answer. It's always best to full length resize your handloads, but it should be done accurately.
Quite often shooters find that their handloads won't chamber without using force. This reloading technique always
shows why handloads don't fit properly. 99% of the time, the problem is excessive case length (at the shoulder) or excessive case width
(above the web).