I still can’t wrap my head around bullets and hogs heads. Then again most of my dead on head shots are generally dispatch type shots with a .22 at fairly close range, 15-20ft.
This is gonna sound stupid and probably is, but for me and calibers it’s a confidence issue. I own several AR15’s but just lack the confidence with them. I’ve killed plenty of deer and even pigs with them shooting 53gr Superformance. But I lost confidence on hogs that run.
I’d lose them because of no blood and them acting as though they were never hit. Buzzards would let me know that wasn’t the case a couple days later!
Probably true. I chose a .223 bolt gun for predators when I switched from deer to predators years ago, then discovered AR's

. It worked great for my conditions and when landowner asked me to cull does and shoot hogs, just kept on dancin' with the gal that brung me. I've shot coyotes w/everything from the ,223 up to 375 h&h (2), just whatever I have in my hand at the moment. Believe it or not the .375 was only 50/50: one drt, the other, I misjudged range on a coyote facing me @ about 150 yards. Held too high thinking he was more like 225 and hit him at the base of his left ear. He went down like he'd been pole axed but jumped up and fortunately started spinning and I got a 2nd shot. There was a hole in his scull and ear was attached only by thin strips of fur on each side of the ear. Just proves that it doesn't make any difference what you're shooting, shot placement is king.
As for the hog, probably need a bit more information of this particular shot. I was sitting on a low chair overlooking a water hole when this boar came trotting over a rise, about 3' higher than my eye level. He had his head down and I aimed between his eyes. I saw the splash when bullet found it's mark and his knees buckled, but he rolled back to his feet, turned and disappeared back over the rise before I could get a 2nd shot....even with the AR!
I've re-run that scenario many times and I believe that, since I was shooting from low position, and due to the shape of a hog's nose, the bullet struck almost parallel to the snout and ricocheted off his skull. He left little or no blood and disappeared into a very dense thicket, so unable to recover. I don't fault the bullet or caliber, just the shooter on that one.
Have taken a lot of whitetails, hogs and coyotes w/223 and don't feel a bit handicapped, other than range with the little quarter bore; have shot out to 300 but conditions gotta be favorable beyond 200. Bet I could count on one hand the number of coyotes, only one hog and no deer that ran with that load over the years.