.300BLK is roughly equivalent to 30-30 in the supersonic loadings, and is perfectly capable of short range hunting of medium sized game.
The advantages in an AR platform is it can use 5.56 mags, and you can build a 5.56 upper to swap on when you're not hunting. It's also nice suppressed with subsonic rounds, although there is a significant change in POI from supersonic to subsonic.
Subsonic .300BLK for HD will give you a much more tolerable muzzle signature than .300 supersonic or 5.56, though ballistics are roughly equivalent to .45ACP.
A .308 makes more sense for hunting if longer distances are involved, but is probably not appropriate for most home defense scenarios.