So it's a 6mm Grendel. Um,...I can't say I'm impressed. While I like the idea of the 6.5 Grendel, the cartridge requires a full length barrel to perform as designed. The same is true of the ARC. And if I'm not going to be able to have a CAR-15 sized envelope, then might as well go just a tiny bit bigger and get an AR10 and have true heavy calibers like 6.5 Creedomore or .243 (if I want a 6mm cartridge).
The one benefit of the 6.8 over the 6.5 Grendel was/is that it does what it does with a 16 inch barrel.
Now if somehow they were to produce something like the ARC that performed in a 16 inch barrel,...I'm game.