Just ran across this thread...good discussion. Hogs are a blast to hunt and we have an endless supply here in central Texas. My brother and I have hunted them together for 20 years and have run AR-15s for the past 5 or so. He uses a 300 blackout and I shoot 6.8 SPC II, both suppressed. You can’t go wrong with either one under 150 yards. We have killed 100s of pigs with those guns. Lots of great bullets for hogs...Barnes, Hornady, etc.
We both switched from the 223 because it didn’t have enough punch for hog hunting. Shot placement is nice in theory but when you walk up on a herd of pigs at night that scatters in all directions, you don’t always have that luxury. Even with the 6.8 I have dropped a 400 lb boar with a shot behind the ear only to have him get up and charge us. Took 6 shots to bring him down. They are some of the toughest animals I’ve ever seen. Btw, I recommend always carrying a pistol if you’re on foot.
As for buying/building the gun, it’s really not too hard to put one together. As others have said, AR performance are some of the best barrels for the money. Anything from 16” to 12.5” is good, especially if running suppressed which I recommend. Palmetto State Armory has good deals on decent uppers and lowers. There are tons of good butt stocks and hand guards. Put a good Geissele trigger in it and an adjustable gas block to compensate for the suppressor and you’ll have as good a hog gun as you can buy anywhere. Happy to provide more details on a build. Happy hunting!