The simple -- and theoretical -- answer is: Energy = Mass x Velocity x Velocity x .5, or (E=MVV/2)
This equation would be quite satisfactory if shots were fired squarely at a solid concrete wall, for example.
The problem is -- in a practical sense -- there's a great deal more to it. For example, how much of the theoretical kinetic energy is, in fact, transferred to the target? This is likely a function of (among other elements) the target's composition, density, and mass, the projectile's angel-of-arrival, shape, composition, and even remote factors like the atmospheric density. Also, in terms of lethality, energy transferred does not precisely equate to tissue disruption, internal/external bleeding, incapacity, mortality, etc.
Many threads on TFL have discussed the criticality of shot placement. The foregoing analysis makes the same key point once again. Greater mass and velocity are likely -- but not certain -- to have more devastating impact, IF the "hit location" is physiologically critical.
However, there is a ton of anecdotal evidence to suggest that even this basic precept isn't absolute. To illustrate, an individual may be struck in an extremity (e. g., the thigh) by a FMJ/military rife round (generally very high velocity and relatively low mass), but sustain comparatively small injures when the projectile passes from side to side without striking an anatomically critical part (a "through and through" hit). On the other hand, a very low mass/very low velocity projectile (from a .22 long pistol, for example) may tumble in the extremity, thereby causing greater tissue disruption and potentially even severing a critical artery. Of note, the physics inherent in this illustration are, in part, why the US Army adopted the .223 round and the M-16 series weapon (low projectile mass but very high projectile velocity) after generations of the .30 round for the Springfield, the M-1, and the M-14 rifles.
[This message has been edited by RWK (edited October 11, 1999).]
