Shot placement on hogs is different than deer. A shot behind the ear doesn't drop them. Mature boar have a thick layer of hardened gristle over their ribs between the skin and muscle. A heavy crossbow might penetrate it, but an ordinary compound hunting bow won't unless it draws 80 - 100 lbs.
Oh well, back to the shotgun and slugs. Glad all I have to deal with is racoons, skunks and possums. Although I don't shoot them, I shoo them away with a stick, except for the skunks who I leave alone. I'm not about to mess with boars.