Is Over-penetration in a self-defense scenario anymore of a concern with this caliber vs any of the other Major calibers?? I read a lot about how this round can penetrate everything but what I don't understand then is why would it be a good choice for SD?? Wouldn't that be a liability?? Why do Air Marshalls carry it, when in such a confined space and potentially dangerous place to be poking holes? Or is it that the velocity will only aid in expansion and energy dump, not punching holes?