556 will kill them it's just will you recover them before they run off into brush if you don't head shot them. Big fields no issue with chest shots...small fields not so good. Was shooting 20-30 pigs per year of my buddies property at night. Ballistic tips don't hold up to the shoulder plate. Tsx work OK and give you two holes.
as far as other calibers... Have used 300 blkout supersonic with tac-tx and had much better luck. No to subsonic unless you are doing head shots on single pigs. Prefer 308 with accubonds. Winchester Silvertip would just delam and you'd find jacket on far side of body.. Some hogs are just too stubborn and amped up to die. I have rolled them with a 308 at 20 yds through the boiler room and had them get back up and charge at me. Literally had to elbow buddy out of way to get two practically contact shots in to pile one up a few years back. 12 gauage 4 buck has been my go to for working in the mesquite flats at night. Shoot them head on...broadside get a further back than you would think on big boars so you get enough penetration into the lungs w/o getting hung up in the shoulder plate.