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Energy may be the most misunderstood, and bandied about term in small arms ballistics, at least as it relates to stopping power. The seductive thing about raw energy is that it seems to make comparisons between different rounds easy, as energy can be easily calculated by a formula and then the energies of different rounds may be directly compared. A lot of foolishness was "proven" by this approach back in the seventies. Because of the high velocities that it's lighter, smaller bullets can achieve, the 9mm can generate more muzzle energy than the .45. Many took this as proof that the 9mm was a more deadly cartridge, even though tests at the turn of the century using living subjects and animal carcasses instead of formulas proved the .45 to be the superior round. For those who wish to calculate energy of various loads the formula is given below, and on the formula and table page.
W x V

    In the above formula W is the weight of the bullet in grains, V is the velocity in feet per second squared, and the bottom number is a constant. The answer given is the energy in foot pounds. Congratulations, you are now a ballistician! You can apply this formula to any load you know the velocity, and bullet weight of. This is not a bad tool for determining what is a major caliber, and for getting a feel for how much power it takes to make a round a reliable stopper, but it should not be considered, as some have considered it, the gospel. Because this number is arrived at by squaring the velocity, but only multiplying by the weight, this formula tends to favor light, fast loads over heavier ones, which effectively means that it will favor a smaller caliber over a larger one. This would be valid only if bullet lethality were primarily dependent upon energy, and penetration alone.
    The interesting thing about this is that these light, fast loads are just the type to make small permanent, but very large temporary cavities. As was shown in the section on bullet placement, the temporary cavity has little effect on most of the body. The organs most strongly effected by the temporary cavity (brain, liver, heart, kidneys) would most likely cause death if hit with or without the temporary cavitation effect. A lighter bullet will tend to slow down much faster, so that by the time it penetrates to a lethal depth in the body it may have lost much of the cavitation potential it had coming out of the barrel. Some of the ultra light, hyper velocity bullets introduced in the wake of these "discoveries" back in the seventies, turned out to be dismal failures in the real world. What most of them did was to dump most of their energy creating a large temporary cavity, or to cause a very large, but very shallow wound, depending upon the design of the bullet. Often this wound was so shallow that it did not even extend to depth sufficient to reach vital organs. This was particularly the case with frangible bullet designs, like the Glaser Safety Slug. What many of the other light fast loads did was to exit the body completely, causing a slight but very real danger to bystanders, and wasting much of their vaunted energy as they continued on for some distance after exiting. This debate has actually been going on for most of this century, the argument over velocity verses bullet weight. Because Energy is a product of bullet weight and velocity, it is possible to have a slow heavy bullet, and a fast light bullet with the same energy. So which is better?
    Before Answering the preceding question directly, I want to set up a little table for comparison.
Projectile Weight (grains) Speed Diameter Frontal Area Energy E / FA
.45 Auto 230 850fps .454 .16 369fp 2306
9MM 124 1000fps .355 .099 275fp 2778
.38 Special 158 850fps .357 .1 254fp 2540
.357 Magnum 158 1250fps .357 .1 548fp 5480
.44 Magnum 240 1200fps .429 .144 768fp 5370
.223 (NATO) 55 3250fps .223 .04 1290fp 32250
.7.62 (NATO) 168 2600fps .308 .075 2522fp 36028
.300 Win Mag 200 2830fps .308 .075 3558fp 50828
Baseball 2188 (5 oz.) 132fps (90mph) 9.000 63.6 84.67fp 1.33
Bowling Ball 112000 (16 lb.) 20fps 27.000 572.5 99.5fp .116
.25 a.c.p. 50 800fps .25 .05 71fp 1420
.22L.R. 40 1140fps .22 .04 115fp 2875
.177 pellet 8.5 1000fps .177 .025 19fp 760
200lb man faling 1400000 10fps 140000000fp
    All of the standard measurements have been included, but what may not be familiar is the measurement in the last column. It is an attempt by me to approximate what the penetrating power of a given round may be. It merely shows how much force is concentrated in a given area by dividing the total energy by the frontal area. This tells how many foot pounds per square inch a round has. This affects penetration indirectly, as the bullet type also factors into penetrating power, but it can be used as a gauge to evaluate the potential penetration of a given round. There are three axis upon which a round will damage a target. Two of them are determined by the diameter of the round, while the third is a product of the penetration of the round. A simpler way of putting it is that two of them determine the size of the hole, while the third determines the depth.
    What is interesting about the above chart is that it shows the fallacy of depending upon high velocity, or weight alone to create stops. A .177 pellet has higher velocity than a .38, or .45 slug, but clearly does not have the lethality. On the other hand, a baseball, or a bowling ball with their massive frontal area, and weight, are not generally lethal, even though they have more energy than a .25 round, and only slightly less than the .22. Recalling that the seriousness of a wound depends upon the depth of penetration, as well as the total amount of tissue affected, some observations may be made using the table above. In a man sized target, it would seem that at least 2000 pounds of force per inch is needed in order to penetrate far enough into the body cavity to cause sufficient trauma. Thus it is not simply the amount of force, but the concentration of force which makes a round lethal. It is estimated that around 20 to 40 foot pounds of force are contained in a knife or an ice pick during a stabbing motion. Clearly this is a small level of force when compared to some of those listed above, yet stabbing wounds can be very lethal, and ice picks are notoriously deadly. What gives a knife, and in particular an ice pick, it's lethality, and penetrating power is obvious upon examination. The razor thin blade of a knife, and the tiny point of an ice pick, greatly concentrate the force applied. If these forces would be calculated and placed on the table above, it is likely that several thousand foot pounds per inch would be listed in the last column for these weapons. These weapons also have a tendency to curve through the body, rather than travel in straight lines, thus producing a wound channel much larger than the instrument used.
    Raw energy is an important factor in bullet lethality, but it is only a factor, and must be properly applied for a round to be effective. Tissues are capable of absorbing and disipating energy; some do this better than others, but all are capable of doing it to a degree. What is required is enough energy applied so that it will be transmitted to the tissues faster than it can be dissipated, causing destruction and penetration. This energy is applied by means of bullet size, weight, shape, speed, etc. but is merely a measurement of raw power, and does not in itself indicate effectiveness. All of the rounds considered to be lethal, because they are able to penetrate to lethal depths in the human body, have between 2000 and 3000 foot pounds of force per square inch. There are rounds with more power, but they are generally considered to be over penetrative, and difficult for the shooter to handle. The Hatcher scale, and certain others based upon the same theories, which take into account bullet diameter, as well as penetration, and energy, seem to have the closest correspondence to real world results.