After you deliver 800 fps of 158 grain hardcast lead payload to the intended target, Penetration Disappointment probably will not be a topic of too much concern.
I think I pretty much said that when I said a wadcutter at 800 fps would be a decent defense load. The OP, however, is talking about 600 FPS and penetration is a concern.
Jim's Rules of Carry: 1. Any gun is better than no gun. 2. A gun that is reliable is better than a gun that is not. 3. A hole in the right place is better than a hole in the wrong place. 4. A bigger hole is a better hole.
no guns = might makes right