What if the aggressor is an overweight POS?
This is needed because not every shot hits directly in front or back of the body, and you may hit an arm on the target's side. Thus, the bullet must be able to penetrate 13" of flesh and bone to reach vital organs and blood vessels.
Knowing that, I don't think there is anything in a pistol caliber, or even many small- and medium-caliber rifle cartridges, that would be approved for use on a Nadler.