You got it! The whole thing is about energy. Dumping the energy inside your target/adversary is what you want. If it goes all the way through and keeps going than not all the energy was absorbed by the target. When I was younger I thought just the opposite. <br /> <br /> Lots of people think that the faster the round the more likely you will have over penetration. Generally that is not true. In my experience we had 9mm fired from a H&K 9mm SMG SD (950-1100 fps.) punch through people while a Fed Match .308 BTH (sniper rifle shot 2750-2800 fps) totally disentergrated and used up all its energy. Ballistics is a very intersting subject. There is a lot to it.