Taken from the book Centrefire Rifle Accuracy which I have previously reviewed, here are three gauges useful to any reloader, but particularly to a reloader who has chambered his or her own barrel.
The first is a full case gauge.
With this gauge, you can see the fit of your brass and bullet. It’s also an opportunity to grade your chambering setup as you can see the cut of the rifling lands. The gauge shown is a 6.5mm Grendel.
Next is a shoulder set-back gauge. This gauge is used to measure the distance from the base of the brass, to the shoulder datum. You can measure cases fired in your chamber and set your sizing die to only bump the shoulder back as much as necessary for your rifle. To make, simply ream a bit of barrel deep enough to cut the case shoulder profile, but not into the body. (If you cut part of the body, you can always face it off.)
The final gauge is barrel and bullet specific, though mostly bullet (the variations in barrels are small by comparison). It is a seating gauge. To make one you cut about neck-deep using your chamber reamer, then trim the other end such that it is 0.100″ longer than the tip of the bullet. In this way you have an COAL gauge that can be used to measure nominal COAL by measuring across the base of the cartridge and the gauge, then subracting 0.100″. This avoids the small, but annoying inconsistencies of measuring across non-uniform tips. This measurement is also much more meaningful as it is closer to answering the question “How far is my bullet from the lands in _my_ barrel?”.
So here are all three gauges – a veritable cornucopia of information for the reloader who wants to control everything.