I've been running a 300aac (Blackout) for a few months now. I re-barreled one of my AR's, 15 minutes and up and running. It does use any regular AR magazine since the round is basically just a necked up 5.56 case. It feeds and functions flawlessly and is a beast within 200 yards. I've actually recently decided to get rid of my Grendel's and go to 300aac as my secondary caliber. The factory ammunition is pretty prevalent now with Remington, Hornady and others putting out multiple loads for it. If I lived out west or somewhere I could take advantage of the long range abilities of the Grendel I would've kept them but in Florida where most of my shots are inside of 100yds the 300 makes more sense.
I did learn something with it though, as a hog hunting round any shots inside of 75yds or so need to be a head shot. I took a quartering shot on a smallish (125lbs or so) hog from about 60yds and the only thing that was still edible was the left shoulder, right ham and about 7 inches of backstrap. It left a wound track big enough to put my arm through. That was with the 125gr OTM round. The cool thing is there's factory ammo available from 110gr to 220gr. The only comparable wound I've ever seen on a hog was a .454 casul from about 15ft. I was looking at going to a .308 AR platform but I'll stick to bolt rifles in .308 and keep the blackout as my mid-range round.