We often hear these studies that demand 12" of penetration or whatever. This is probably true depending on the circumstances. For the military, people are behind cover, they are wearing armor, they are wearing helmets, they are in armored vehicles, they are wearing rucksacks etc. As a civilian, odds are, if I had to use one of my .223s for self defense, it would be between 10'-20' or the distance between walls in my house. Again, odds are, the guy would not be wearing armor or other equipment, and I live in the desert so his clothing would be something like a T-Shirt. I would also imagine that if I had to defend myself, I would definitely be shooting more than once. I feel fairly certain that the V-Max would work like a charm. Now don't get me wrong, I don't think it would make a good military bullet; but for civilian self defense I think it would work well.
As far as hunting is concerned, I use the .223 for varmints. 99% of the time coyotes and jackrabbits. I can assure you that they are a great bullet for what I use them for.
Overpenetration isn't really an issue for me. I live by myself in a rural area. But, that being said, the V-Max would be very unlikely to overpenetrate.