7mm Valkyrie is a great wildcat cartridge. And with the new 6mm brass that's become available, much easier to form the brass. If you want a similar 6.8/.277 caliber, then the 270MSR (improved 270AR) is available via AR15 Performance. Only negative, it's a wildcat.
But a 6.8 ARP barrel makes a great hunting AR. I prefer a 16" barrel for the balance and less weight. I currently have ARP barrels in .223 Wylde, 6.8, 270AR, 6.5G, and 6.5 CM. All have grouped around .5 MOA at 100 yards. You can't go wrong with ARP barrel.