Creedmoor, chamberings independent of bore diameter have been engineered to take advantage of where the $$ has gone with respect to projectile development (and advertising). It's not a fad, it's a better mouse-trap. You give up just a little case capacity to gain a repeating rifle, that allows and OAL up to and even into the lands while still staying within the confines of standard magazine lengths (2.8"). Couple that with bbls that are twisted such that they'll also be able to maximize current and likely future developed high-BC, long projectiles. Previously (and currently), regarding "the old standbys", unless one paid a gunsmith to chamber a barrel throated in such a way as to meld the max OAL of the chamber with the max OAL allowed by the magazine the shooter was relegated to either a LONG jump to the lands, or shooting single-shot because loaded rounds wouldn't fit in the magazine.
Federal brass is shitty.
Don't know what to think about the bbl with the sleeve and magic cooling potion. In benchrest, actions have been sleeved for decades to increase rigidity. I can say for certain I haven't the foggiest idea what's going on inside the AL bbl sleeve on the Dracos.
Draco from the Harry Potter series was a spineless, whiny, shit-heel. That in itself might keep me from buying the barrel. :::