Are we talking 7.62x54R or 7.62x39mm? If we're talking 7.62x39, the .220 Russian was based off of it, or maybe the other way around, I'm fuzzy on that, and the .220 Russian was the basis for both the .22 and 6mm PPC.
If we're talking 7.62x54R, I don't know of anyone that's done it. I can't imagine it's any more "kinda big for a 6mm" than the 6mm-.284 or the .240 Weatherby Magnum. It might even make for some interesting modified Mosin-Nagant rifles firing 6, 6.5 and 7mm bullets.