Another new one on me, after pulling up some data I can't see much difference than the 6mm-TCU or 6x45AI that have been around 40+ years. It's made from 350 Legend brass which seems pretty much the same as 223 Basic brass.
Clue in an old fart if I'm really off base.
Thanks
AWS
its a factory loading thats exceeding 6-TCU published velocities with the same bullet by between 400-500 fps (give or take a few fps) out of a similar length barrel (14" for the tcu vs 14.5 for the max) according to hornady's published reloading data on the TCU.
thats a relatively significant gain.
with the cartridge, you gain +4 grains of h20 worth of case volume vs the 223 case family with the same case head as a standard 223/556 bolt.
so we finally have a 6mm class 35 grain water capacity case that can run on a standard .378 bolt face in the ar platform which allows it to handle a higher pressure round than other cartridges with similar case capacities - many of which are running the grendel type 2 bolt face, and therefore limited to its pressure capabilities (52k psi).
being parented off a cartridge which is rapidly being accepted as one of the easily accessible and extremely functional whitetail cartridges also means that product support for the basic foundations should be available for a long time coming. i dont think many can argue that with its rapid acceptance into the whitetail hunting world that the 350 Legend is going away any time soon.
re legend vs 223 basic brass - not really the same thing. the start from the same brass cup, but the legend is not parented off the 223 case family. the body diameter is larger - the legend has a true rebated case rim - and its not something that can be fire formed into existence. someone might be able to come up with a way to swage the 223 basic into legend, but at the very least it would require a complete body annealing and more than hobby level off the shelf dies to do so. so yes they source from the same raw starting point, but practically speaking thats really about it.
