IMO........the 6.8SPC in a 1:10 twist bbl is pretty much equal to a 7.62X39 or a 30-30Win. This,depending on which bullet is used and what action it is fired in. The other chambering,6.8SPCII, gives pretty much any weight bullet(.277",85-125gr)approximately another 100fps. My opinion is that the 6.8SPCII will deliver about 70% of the power of a medium loaded 308Win.
The bullet selection for a 6.8 is somewhat limited by the action it is used in,and the mag. My 6.8SPCII is a AR/Bison side charge. It is my dedicated night hunting hog/coyote gun and this year will be doing some night time deer harvesting with a predation permit. My gun has a 18" bbl and is fairly heavy. IMO it has about the same recoil as a 7.62X39 AR.
I have been shooting the Barnes 85gr TSX but have switched to the 115gr Fed Fusion for the deer control(with permit). My weapon has a ATN ThOR 320 3X 60hz. thermal on top. --- pruhdlr