AR's are fine for small to medium soft bodied game like spanish goats, feral sheep or even small axis does when shooting for its vitals.  I recommend that u use a good hunting round 62 grain or heavier to assure good penetration and a humane kill.  As far as pig hunting, using this round is adequate for small immature pigs which by the way should be allowed to mature before being harvested unless absolutely necessary. When shooting mature pigs through its vitals this round will more likely injure the pig reducing ur chances of recovering it.  The only humane way to kill a mature pig with this round is with a brain shot.  Some people do recommend neck shots to bring down large game but sometimes miss its intended spine also injuring the fleeing animal. If u are unable to make an accurate brain shot with an AR then u should invest in a hunting rifle with a larger adequate cartridge for the game u wish to hunt.  I have hunted all of our game mammals in Hawaii and have observed individuals using all types of methods but have come to realize that its better to be safe and make a humane kill then waste or maim an animal for your mere entertainment.