I'll try to seek some to set an example. So in the post where I went on about sectional density and was acused of not saying anything. I think I get what youre saying by not addressing the starting line. Its because once the bullet enters the animal it changes shape, mass, and speed as it goes through the body. Therefore the sectional density of the projectile changes while inside the critter. If the projectile comes apart, it becomes more projectiles, slows way down, and sectional density decreases rapidly and wont penetrate as far. If it stays together and holds its mass then the sectional density wont change as rapidly and will penetrate deeper. I think what I said before was true until the point of impact. Is this closer?