(I'm the AC who originally posted; I wasn't logged in then.)
But it's nice to know they somewhat cater for the Liberians, the USAmericans and the rest of the world.
Oddly enough, a .30-06 is only called 7.62x63mm. That's the metricified name for it... but not the actual dimensions of the round: the bullet diameter is 7.8mm, not 7.62mm.
Cartridge names look like they're dimensional quantities, but they're not, and really never have been. The .38 Special and the .357 Magnum fire the same size of bullet. (In fact, you can fire .38 Special from .357 Magnum revolvers.) The German-designed 7.65mm Parabellum cartridge actually fires bullets 7.85mm in size. The Russian 9mm Makarov is actually 9.2mm. The 9mm Parabellum and 9mm Short fire different sizes of bullets, too; one is true 9mm and the other is smidge larger.
Moral of the story: the name is just a name -- it doesn't actually reflect the size of the cartridge, and for that reason there's no reason to prefer metricified names.