It isn't if they can be killed. You can kill LARGE boars with .22 subsonic if you know what you are doing. It really comes down to a question of how well a given caliber/bullet/load will kill for all the times you don't get to make those perfect sort of aimed and placed shots. This guy claims this hog is 400 lbs. I don't know if it is that big, but it is a plenty substantial hog... I have never had a problem with a centerfire rifle round penetrating a hog shield. It is nothing but a cartilagenous buildup, probably no more significant than 1/4-1/2" plywood. It is more of a cut resistant vest than a level 3 ballistic vest (rifle rated). They really aren't a whole other animal. That some guy got charged and it it took a lot of shots attests to nothing other than the fact that the first shot didn't do significant CNS damage. Once the adrenaline dumps, hogs likely will not be stopped unless you physically break them down (CNS damage, locomotor damage) or they die from blood loss or suffocation. It doesn't matter if it is a European wild boar for a simple feral hog. There really are not much in the way of true European boar in the US except maybe on a few game ranches. Those out in the wild have crossbred with feral hogs, likely many times over. I know everyone and their dog likes to talk about how much "Russian" a given hog has in it, but a lot of that is bunk. Just because a hog has a razorback or a long snot, or straight tail does not prove anything about being Russian (aka European wild boar). There are domestics with all those traits as well. Short of a multivariate craniometric analysis or genetic test, you really can't say with any certainty how much domestic, feral, hybrid, or European lineage is in the hog...and it really doesn't matter.