At some point though, speed creates a greater lethality than mass. If that were not true, a 12 ga. slug would have more knock down power than a 300 Weatherby. The real question is; at the same calculated muzzle energy, which has the greater lethality; a small caliber moving fast, or a larger caliber moving more slowly. And, which transfers the most energy to the target? When a bullet exits a target (such as the back side of a deer), there is no more kinetic energy being transferred.