lol! all things new... compare a 10MM/40 to a 38-40! Dang near same ballistics, just in an auto! And (w/o looking!), I think the 38-40 can best the velocity of the 40, if not the 10 - and maybe even do it with Holy Black!!!
And your ref to the 6.5. 6.5x54 and 6.5x55 are very old. Rem failed with the 260 - even tho it is a fine cartridge. Real trick to the 6.5, imo, is that it is a short action. In an AR, i would lean to a 6.5 Grendal. In bolt gun 6.5 Creed all the way. Buddy shoots long range. At a training class, he was smoking the 308s past 600 yds. Said 1200 yds was pretty easy. And the latest LR bullets for calibers are now .680-~.760! unreal!