Thank You Gunman;
This "Attal" post effectively describes the conditions prior to adoption of SAAMI & CIP Specs & is the precise reason a single plug gage per Gauge size cannot be depended on to give an accurate measurement of chamber depth in all cases. In fact most of those guns in which it would be accurate will have chamber length marked anyway.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra