The largest hog we killed was shot with a .223 in the ear though I've also seen the bullets bounce of their skulls if you don't hit them right. We hunt them at night with a light and you have to snap shoot so a body shot is the easiest target. So we always use a large caliber we can get through the shield. I've shot one 350lb boar with a .35 remington and it didn't penetrate all the way through the shield from 65 yards. It stopped underneath the skin on the far side so it takes a large gun if you are going to shoot through the shield on a large boar. Right now I shoot a .450 Marlin and it will drop them regardless where I shoot them. So once the light comes on and I line upon the shoulder we shoot. It will put a large hole through them even through the shield.