I have both. Like Dirty Dog, I saw no use in the 300BO. But, I have to say that I was wrong about it. I am running 110 grain Vmax at 2400 fps in my 16" upper and 2100 fps from my 9" pistol. It's just about AK horsepower with AR accuracy and function. It is more accurate at range. The 6.8 has more Horsepower for sure, but I like making 300BO brass and it's really cheap. I shoot my 300BO's way more often than I do the 6.8 SPC.