The nearest factory round to that designation is the (late?) .307 Winchester, as Joe says. .30-40 would be longer, and I've never seen the metric designation actually marked on a rifle--the few continental rifles I've seen chambered for .30-40 used the inch/US terminology. All were Belgian. (Isn't the .30-30 metric designation 7.62x52R?). .307 wasn't around long enough for me to even have fired one!