Odds and Ends
9 8, 12:46am
Not really. 9mm Parabellum was so named before it got adopted in the US. If we had really adopted metric we would be shooting 9mm ACP shorts instead of .380 ACP, 9mm Smith & Wesson short for .38 special, 9mm Smith & Wesson long for .357 Magnum, and 11.4mm ACP Short for .45 ACP.
Mostly anything adopted after the 1940's was adopted as a metric cartridge in order to align better with customary NATO countries. So .308 became 7.62 NATO and .223 is .556 NATO and so forth.