6.8 is just more efficient than the Grendel in barrels under 22". Yes, the Grendel beats it past 300, due to BCs and longer barrels, but for 300 and in in a lightweight, handy package, the 6.8 makes a better case. The issue with the 6.8 (initially) was Remington totally screwing up the case/chamber/twist.....hence the specII and 1:11. Sure, there's others in the class, but few with factory load options and equal performance vs recoil vs blast.
