As CH states, this is a varmint bullet, designed to explode little furry creatures up to 20 pounds. It is designed to expand immediately upon impact, which causes it to have shallow penetration. This is true of anything loaded with varmint bullets (such as Hornady V-Max and the .223 TAP loads up to 60gr).
When your life is on the line, you want ammo that is going to get the job done regardless of the circumstances (such as: the angle you are to your attacker, or if you have to shoot through an arm). In a real defensive situation, you'd almost never get a straight-on, bare-chest, "standing at attention" shot. That's something that only snipers are likely to get, and even then, only occasionally. Assume the worst case, not the best case, and choose your ammo accordingly.
-Troy