I was in the same boat last year, but after seeing the grendel gets optima velocity with longer barrels i went with the 6.8 using a arp barrel. Im getting 2440 with factory 120 set out of a 12.5" barrel and 2680 using the federal xm6.8.
I have yet to reload for the 6.8 but many are getting up to 200 fps more velocity safely using the 120 sst then the factory ammo. Im fixing to build me a 16" 6.8 also. I dont shoot out past 300 yards so the 6.8 fits me perfectly.
