Sorry for reviving this old thread but I do have some experiences with my 18.6" Robinson Arms XCR-L in 6.8 SPC 1-11" twist spec 11 chambered rifle that may interest you.
My favorite bullet for hunting that was designed specifically for the 6.8 SPC is the new Barnes 95gr TTSX I load them with Rem LR primer brass, 30grs H322, Win LR primers & lightly crimp with a Lee factory crimp die this load = 2825fps.
Here are a couple pics of a rock I shot @ 350 yards you can see 2 hits and the 3rd shot hit in the sand between my thumb and the bottom left of the rock.
Pic of the shot rock is located 20 - 30 ft to the left of the top of the light coloured log.
Recovered 95gr TTSX shot into very soft sand/moss @ appr 330 yards.