This is where the nomenclature gets used in the wrong way.
Calibre is the diameter of the bore.
Chambering is the correct term to use but no-one does.
A .308 Winchester rifle and a .300 Winchester Magnum rifle are both the same
calibre, i.e 30 calibre..
One is
chambered for the .308 Winchester cartridge, the other is
chambered for the .300 Win Mag cartridge.
The various firearms registries all incorrectly list firearms as calibre not chambering. .308Winchester is
not a
calibreSorry if I'm preaching to the wrong audience, but is something that really irks me.
Rant over.