I use an AK variant and find it is perfect for hogs in the brush I hunt in being that all shots are within 50 yards and sometimes very rarely I get a 75-100 yard shot. I use hollowpoints and have dropped every hog I've shot. A well-placed shot (head or high-neck) with solids should also work. As far as hunting ethics go, I don't see hogs as game. They root our pastures so badly and destroy fences so that it costs us money. I will not pass up eating a smaller sow under 150lbs, but anything bigger we can't seem to even give away, so we drag them to a corner of the pasture where we won't smell them much and let them feed buzzards. Hogs are ag-pests to us- no different than a big rat would be in your home.
As far as the .22 goes, I don't recommend it, but my brother-in-law's father has downed many pigs with one. He shoots the spine somewhere and claims they rarely run more than 20 yards. He likes to stun them so they'll bleed out quickly and taste good. He lives in the woods of deep-East Texas and is probably as good at killing hogs as I am at killing beers, so my guess is that he has developed his own way that works for him. I can say that at least he eats them all. It must be something they eat on our ranch that makes them taste so awful because other people here and elsewhere swear they taste great, but few of mine ever tasted any good.
If I cleaned all the hogs I killed, I could probably feed all the orphan kids in the State of Texas but after one bite of the biguns, they'd never eat another bite. I don't know why I draw such a line between deer and hogs. I'll take just about any shot I can on a hog (because they cost me money), yet, this deer season I passed on 26 deer that I couldn't get a head-shot on. Maybe it is because deer don't cost me anything and don't tear up anything but g'ma's roses (which I think is pretty funny anyway).