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Departments : Officer Survival

Understanding Stopping Power

Choosing a defensive handgun requires you to balance power and accuracy.

January 01, 2003  |  by Roland C. Eyears

Choosing a Compromise

Let's go back for a minute to our discussion of what it takes to shut down an attacker. You have to hit the target and you have to hit it as hard as you can. These two goals, while by no means mutually exclusive, are difficult to achieve. Consider that it's much easier to keep a small caliber handgun on target, but the bullets may not have the mass and the energy to shut down the threat as quickly as you need to.

Put simply, this means that all defensive handgun choices are a trade-off between what you can control and what it takes to do the job. Let's look at the pluses and minuses of some possible choices.

"Dirty Harry" fantasies aside, the .44 magnum may be eliminated from consideration as a defensive handgun because the hardware is almost invariably too big and too heavy to carry or conceal. Moreover, with recoil more than twice that of its nearest competitor, recovery and a follow-up shot are improbable. Does it offer stopping power? You bet. But this bear killer's penetration potential raises serious liability questions in an urban setting.

Should you or a friend want to max out your stopping power short of an unwieldy .44 mag but stay with a .44 revolver, consider Dirty Harry's cartridge of choice. He fired .44 specials in that big Model 29.

The .357 magnum is a proven stopper. But here again there is more recoil than many shooters find comfortable, and the .357 revolver is famous for high muzzle flash, which ruins night vision-a serious consideration since most self-defense shootings take place in low light or no light.

Many officers carry 9mm autopistols. And this weapon does have its advantages. The size of the round means that your magazines can carry more "bumblebees," and the slight recoil of the "nine" makes it a good choice for accuracy, but it may not hit hard enough to do the job. A 9mm round barely reaches the energy of a hot 38 special.

Let's discount the 10mm. It never quite caught on. The hardware is hard to find, and the ammo sources have all but dried up. Its offspring is, however, highly popular.

The 10 Lite, aka .40 Short-or as Smith & Wesson likes to call it, the .40 S&W-has become one of the leading law enforcement rounds in just a decade. This trend can be traced to a bloody 1986 incident involving FBI agents and bank robbers. Two agents were killed and five badly injured in a 140-round shootout in Miami in which the criminals were struck many times by pistol rounds and shotgun pellets yet managed to stay alive and deadly for minutes after they were mortally wounded.

In the aftermath of the Miami shootout, the Bureau was not about to admit to faulty tactics. Blame for the unfortunate debacle had to be laid off on the lack of the right equipment. The conclusion was that the good guys didn't have the right guns and ammunition.

In their quest for the magic weapon, the FBI conducted a series of five-round tests, which would have been an embarrassment at a junior high science fair. With that, they dismissed the .45 ACP as "already fully developed," whatever that meant. The 10mm was judged too hot to control and possibly overly penetrative. But by down-stepping the power on the 10mm, the .40 was born. The FBI had its magic bullet. Its father was organizational ego, its mother posterior covering.

Police rounds are specifically designed for power and expansion.

But is the .40 S&W all it's cracked up to be? As the JEDI chart reflects, it is a more powerful round than the .38 or 9mm. However, Whit Collins, the man who conceived the .40, warned that while it was designed to be a superior replacement for the 9mm, it would never equal, much less exceed, the .45 ACP.

So what compromise will most efficiently produce the ultimate in behavior modification and accuracy?

Within the range of .38 specials through .45 ACPs, hardware abounds to satisfy the requirements of small enough, light enough, concealable, manageable enough, and socially acceptable. Picking from both ends of the mid-spectrum, lay a snub .38 atop a .45 ACP Colt Officers Lightweight. They are of the same length and height. And at 24 ounces, the 8-round autopistol is just five ounces heavier than the five-round snub revolver. But when it comes to stopping power there is no comparison.

About six years ago, a leading gun magazine asked 10 nationally known shootists/gunsmiths to name their preferred defensive handgun cartridge. All 10 opted for the .45 ACP.

Your pick will depend on your comfort level. Most of us have heard people say they never could hit with a particular caliber or that they can't seem to miss with another. Whatever feels best in your hand and you are able to carry with confidence should be your choice. Just remember to partner your weapon of choice with a cartridge that has adequate stopping power.

May the Force Be with You

Typically, muzzle energy measured in foot-pounds is used as a quick-and easy-measure of stopping power. Most of us scan a chart published by a major ammo manufacturer and see, for example, that a certain 9mm round shows 362, while a .45 ACP comes in at 356. Equal? Not that simple.

Although kinetic energy figures are handy keys, they are not a valid reflection of stopping power. Because the formula for calculating muzzle energy requires that bullet speed (by far the largest number in the mix) be squared, the power factor is distorted in favor of a smaller, lighter, and faster projectile.

M. L. Josserand, the long-departed French physicist and mathematician, developed an energy delivery formula that offers a much better gauge of stopping power. The Josserand formula factors in the projectile size by multiplying the standardized kinetic energy at the muzzle by the cross section (area) of the bullet.

To determine the standardized kinetic energy of a cartridge, first multiply the bullet weight in grains by the velocity in feet per second squared. Then divide by 7,000 (the number of grains per pound). You must then divide that result by 32.16 (the constant of gravity at sea level) to reach the muzzle energy in foot-pounds. Or you could just look this figure up on a chart.

Calculate the bullet cross section, or area, by squaring the radius and multiplying that number by pi (3.1416). Multiplying the area by the muzzle energy gives us the Josserand Energy Delivery Index, or JEDI.

As the accompanying JEDI chart reflects, any ammo below .38 special yields very limited stopping power. Yes, the peewees may be better than no gun, but not by much.

At the other end of the spectrum are the long guns, herein presented for comparative purposes, and the .44 magnum.

Sgt. Roland C. Eyears is an Ohio Police Firearms Instructor and an 11-year veteran of the St. Louisville (Ohio) Police Department. This is his first article for POLICE.

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Comments (3)

Displaying 1 - 3 of 3

Samuel, Reich @ 7/6/2013 8:17 AM

If your aim point is the chest and you are not shooting through barriers: Human lungs have a density only 1/3 that of water and there is only 2 or 3 inches to get inside the chest cavity. Therefore in that case rapids expansion is much more important than penetration.

m2foster @ 7/18/2014 6:02 AM

Human lungs are also protected by ribs which would require that you shoot them between the rib spacing, and since the lungs are located above and outside the center of mass where most people are trained to aim, wouldn't you be relying on luck to get that shot where rapid expansion is a bigger factor than penetration?

gsparesa @ 11/20/2014 4:29 AM

I believe that I found an error in your muzzle energy calculation description. You forgot to take 1/2 of the bullet weight times velocity in feet per second squared. The formula according to Wikipedia:

Ek = 1/2mv^2 * (1/7007*32.163)
Ek = Muzzle energy in ft-lbf
w = Weight of bullet in grains
v = Velocity in FPS
7000 gr per avoirdupois pound
32.163 ft/s^2 acceleration due to gravity

Given the above formula, I calculate that the muzzle of a 230 gr 45ACP to be 351.88 Ft-lbf and not 345 as depicted in the chart.

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