At least in America, we have to denote that. If we say 7.62, it could be>7.62x39>7.62x54r>7.62x51>7.62x35>7.62x25>7.62x53 (yes it's a real caliber, from Finland)
And some others that I can't be fucked to remember. So yeah, we have dumb names for each caliber because of the common 7.62 bullet
7.62x39 (soviet, russian, hell I've even heard "slav")
7.62x54r (rimmed, russian, Mosin)
7.62x25 Tokarev or Tok
7.62x35 (300 AAC or BLACKOUT if you're feeling edgy)
7.62x51 NATO or Winchester
This shit is almost as frustrating as differentiating 9mm, but I'm not going to get into that one tonight.