Stinging Jellies: Is there a practical way to abbreviate metric cartridge names in spoken language?

Because saying “seven-point-six-two-by-fifty-one-NATO” is a mouthful compared to “three-oh-eight,” and AFAIK they refer to pretty much the same round. I can say “three-oh-eight” and avoid the trouble, but what if I’m talking about the “seven-point-six-two-by-fifty-four-R,” for which there is no Imperial analogue?