This guy is misleading. Nobody uses armour piercing bullets for hunting.
So it wasn't likely armour piercing, nor would it need to be. In fact, a softer bullet that. expands more, provides more 'hydrostatic shock' and causes more traumatic soft tissue damage thana jacketed or AP slug. Level IV is a hard plate, not soft body armour.
If it was a (expanding) lighter weight jacketed soft point (not fully metal jacket) it is not unthinkable that it would not exit his body if he was hit slightly slouched over. I put a yellow arrow over a pic I fond online to show what I mean. It's just approximate to show a possible bullet path. Then consider that the lateral/diagonal/cross body component of the trajectory could add more meat to step the bullet.
The neck and shoulder muscles, spine, shoulder blade etc would cause the bullet to 'mushroom' or otherwise deform as designed, and soak up a lot of the bullet's energy. And if it hits bones, the bullet can tumble and fragment. Actual wound channels are highly variable in every shot.
Having said that, a 30.06 is a bear of a cartridge and I admit to being initially surprised, and said so previously in this thread, that it didn't blow out the back of his body and splatter blood all over the background signage.
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And IF he was slouched over this much (he wasn't- pic posted for exaggerated effect of importance of trajectory) at the moment of impact, then the slug would have been buried in his torso.
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