For the same hole, caliber can be measured as land to land (british) or groove to groove (european). But by measuring bullets, it won't be that confusing.since when?
must have been before the 30WCF or the 30US. which if you ask anyone will tell you they are 30 caliber...
caliber has ALWAYS refered to the hole drilled into the bar..... When did the gunsmith/barrelmaking industry change the nomenclature?