I agree that I wouldn't use it hunting, I think both the 6.8spc2 and the 6.5 Grendel are better suited there if you want to hunt with an AR.
However a small whitetail out to 200-250 yards or so would be an ethical shot with 300blk IMHO. Same with pronghorn or hogs. Problem with pronghorn, they are oftena further shot than that.
An elk within 100 yds would be OK too.
But like I said, I would want more gun for any of those species.