In my early sixgunnin’ years I religiously measured the groove diameter of sixgun barrels by tapping a pure lead slug down the barrel with a wooden dowel and then trying to measure the diameter of the bullet. Enlightenment came when I finally realized the barrel diameter was not the most critical measurement; it was the chamber throats of the cylinder which matters the most as cast bullets would be passing through these tunnels long before they arrived at the barrel rifling; the less distortion when they get there the better.

When this became apparent to me I stopped measuring barrels, and with .44 and .45 sixguns, gathered sizing dies from .428" to .432" for the .44 and .451" to .454" and simply used the largest bullet which could be pushed through the cylinder throats. I cannot tell you the barrel dimensions of any sixgun I have, however I can tell you the exact size of the chamber throats.

Several years ago I purchased a set of steel plug gauges measuring from .250" to .500" in increments of .001" and they have turned out to be one of the most important tools on my reloading bench.