Most of my hogs have been killed with a .50 muzzleloader using either the 240grain .430 XTP bullet or the 250 grain SST/Shockwave. Have also killed a lot of hogs with a .223. The .223 is a very good hog killer when you hit them right.
Proper bullet placement is everything. Was hog hunting with a friend when he gut shot a big sow with his .300 Win Mag and his whiz bang 180 grain bullet. That hog ran into a plum thicket one half mile away. We jumped it out of the thicket and he gut shot her again. That hog ran another 200 yards before it died. The guy wanted me to show him how to field dress that sow. I had a better idea: He gutted that sow under instruction-what a mess.