Any caliber will work for a hog . . .just like what has been said aim just behind the ear. I usually shot them with a 30/30.
I killed a 350 lb domestic boar once by just whoping him across the forehead with a rotten pine limb. We were trying to herd him into a stall for a vaccination. One tap and he was down . . . .my dad was'nt too impressed.
I can't tell you how many people I talk to tell me about all the pigs they have shot but never found.
You value your pigs, I can't tell you how many hogs have been shot and never even looked for. To us their a pest.