I've never hunted wild boar or wild hogs. Don't want to, either. Nasty looking beast you've got there. However I shot a lot of domestic hogs with a .22 rifle when I was just a kid helping my grandfather slaughter hogs on his farm - a long, long time ago now. (I always used his Remington bolt action rifle; and used standard .22 Long Rifle non-hollow point rounds)The distance was maybe 6' or 8'. They always went down on the knees of their forelegs just like they'd been hit in the head with the back of an ax (which was the other favored way of killing hogs where I came from). I can't properly say I killed any of these hogs; my grandfather actually killed them when he jumped into the pen with them after they'd been shot and cut their throats with a razor sharp Barlow pocket knife, causing them to bleed out. (He was forever sharpening that knife.) Anyway, those .22 bullets were always found deep in the innards of those hogs, having passed through skull, brain, and neck and on down about midway the hog as I recall. I don't know if wild hogs have thicker skulls than domestic ones do, but if not, a 9mm ball round should have penetrated your hog almost from stem to stern, although if you didn't hit him in the brain, it might not have stopped him. Your problem with lack of penetration was probably caused by using hollow points which hit something really hard at high velocity causing it to immediately pancake and stop penetrating.
