I am thinking 200 max range
I checked google images for a trajectory chart for 6.8, and what I saw said there is a 4.7" drop at 200 yards (with a 100 yard zero). I'd sight it 2" high at 100, and use a 2 MOA red dot such as an Aimpoint Pro. If you're a holosight guy, an EOTech 512 would work nicely as well with its 1 MOA dot.
That setup would pretty much be on the money from zero to 200y, give or take a couple of inches at 0 (sight offset), 100, and 200 yards.