A wild boar isn't considered a game animal. It's an invasive pest. You are basically doing an extermination, not a hunt. So you are not constrained by game hunting laws.
You sound like the funny guy who commented on some of my hog hunting videos, proclaiming I was not a hunter, but an exterminator. I am sure it was meant as a put down, but the alternate title works for me.
Last I checked, the reason for putting down the animal does not affect whether you are hunting or not. I use the same techniques and tactics used by deer hunters, predator hunters, elk hunters, etc. for hunting hogs. I have a hunting license. Hunting laws pertain to my hunting of hogs. I am a hunter, LOL, by law. I don't have an exterminator's license, however.
In fact, I don't know of a single state with feral hogs that doesn't have hunting laws pertaining to their procurement. Some states have seasons. Some states have tag restrictions. Many states may have less restrictive laws than they have for other animals, but they still have
Convert your 223 to a 6.8 SPC and use 120 grain SST. Hit them in the center of the neck=D.R.T.
If you can hit them in the center of the neck, .223 will work just fine. The problem is that so many folks can't hit in the center of the neck.