Thread: Caliber names

So, the .303 caliber is actually .311" in size. But the .308 caliber is actually .308" in size. However, .308 is also called "7.62 NATO" despite .308" being 7.8mm. Also, "7.62x39" (which may pre-date 7.62 NATO?) is actually .311". 7.62mm is 0.300".



The .223 caliber is actually .224", or 5.68mm, but it's also called the "5.56 NATO". .224 and .220 are also .224", as is anything called ".22", but .222 (which used to be .222") is .223". 5.56mm is actually around .219", so who knows where that came from.



The 6.5mm caliber is .264", despite 6.5mm being .255" (While the ".25" family clock in at .257".)

7mm is actually .284" which is somewhere around 7.2mm, but maybe that's just lazy rounding.

I'm aware that this is mostly a series of historical accidents and "near enoughs", but did nobody ever stop and think "this is getting a bit out of hand, perhaps we need to rethink our naming system"?