Monday, May 5, 2008

Other Hypotheses of Handgun Stopping Power

These hypotheses are a matter of some debate [9] among scientists in the field:

Hydrostatic shock
Hydrostatic shock is a theory of terminal ballistics that wounding effects are created by a shock wave in the tissues of the target. Evidence of such shock can be seen in ultra-high-speed images of supersonic bullets passing through various objects such as fruit; the fruit explodes due to the shock waves caused by the bullet passing through at high speed. This theory however is only applicable to high-speed ammunition such as rifle bullets; handgun ammunition provides insufficient speed and energy to duplicate these effects. "Hydra-Shock" handgun ammunition is therefore technically a misnomer; a bullet so named achieves its wounding capacity through expansion, ensuring maximum energy transfer and a larger permanent cavity than a nonexpanding bullet.


[edit] Energy transfer
The energy transfer hypotheses states that the more energy that is transferred to the target, the greater the damage that is caused.

This theory is frequently referred to by Kennedy assassination theories, who cite the Zapruder film, which shows Kennedy's head recoiling backwards from a shot, as evidence that therefore, that shot must have been fired from in front of the limousine rather than from behind, where Lee Harvey Oswald was claimed to be firing from the Texas School Book Depository, implying a second assassin. However, it has been repeatedly demonstrated, most recently to a large television audience by Penn and Teller on May 9, 2005 on their Showtime network program, Bullshit!, that when a simplified physical model of a brain inside a skull, composed of a melon wrapped with strapping tape, is shot in a similar fashion, the melon recoils backwards, towards the gun; evidence that the actual transfer of energy from a bullet passing through a complex object is much more complex than simple mathematical models based on oversimplified physical assumptions can predict, a priori.

However, it remains a general physical principle, that when a volume of energy is transferred from one medium to another, the greater the volume of energy, the greater the destructive potential.

In ballistics, energy is a function of velocity and mass. Generally speaking, bullets which impact a target with greater energy cause greater damage. A bullet with too little energy might not penetrate the target - although in the case of a living target they may suffer blunt force trauma, possibly resulting in internal injury solely through the force of the impact.

Overpenetration is detrimental to stopping power with regards to energy since a bullet that passes through the target has not completely shed all of its stored energy. However, the increased tissue damage as well as the creation of an exit wound (and increased blood loss) resulting from a bullet passing through a person also affect whether the target is likely to be incapacitated. Bullets that pass out of the body may still injure people nearby.

Rifles commonly propel bullets to speeds of at at least 2-3 times the velocity of the most powerful pistols. Such bullets have more kinetic energy (kinetic energy is proportional to the square of the speed). Bullets not intended to expand such as the 5.56 x 45 mm NATO, M855 Ball Round, may cause much more tissue damage as a result, than of expansion or fragmentation of a bullet at handgun velocities.

As discussed above, there are many factors that affect "stopping power." Energy transfer is undeniably related to destructive potential; however, the importance of energy transfer in determining the stopping power of bullets (when compared to other factors like location of the wound and bullet size) is not a topic of agreement.

It is a general principal of physics that the force between the bullet and tissue is equal to the bullet's local rate of energy loss, dE/dx (the first derivative of the bullets kinetic energy with respect to position). The ballistic pressure wave is proportional to this retarding force (Courtney and Courtney), and this retarding force is also the origin of both temporary cavitation and prompt damage (CE Peters).


[edit] Knockback
The idea of "knockback" is a subset or simplification of energy transfer theory, and states that a bullet of sufficient caliber at sufficient speed which transfers all its energy to a subject has enough force, by sheer momentum of the bullet, to stop forward momentum of an attacker and knock them backwards or downwards. The idea was first widely expounded in ballistics discussions during American involvement in Philippine insurrections and, simultaneously, in British involvement in the Caribbean, when front-line reports stated that the .38 caliber revolvers carried by U.S. and British soldiers were incapable of bringing down a charging warrior. Thus, in the early 1900s, the U.S. adopted the .45ACP cartridge in what was to become the M1911A pistol and the British adopted the .455 Webley caliber cartridge in the Webley Revolver. The larger cartridges were chosen largely due to the Big Hole Theory (a larger hole does more damage), but the common interpretation was that these were changes from a light, deeply-penetrating bullet to a larger, heavier "manstopper" bullet.

Though popularized in television and movies, and commonly referred to as "true stopping power" by novice or uneducated proponents of large powerful calibers such as .44 Magnum, the effect of knockback from a handgun and indeed most personal weapons is largely a myth. Because of Newton's Third Law, "for every action, there is an equal and opposite reaction", a handgun bullet propelled with sufficient force to arrest forward momentum or impart backward momentum in a human-sized target mass would impart an equal force to the shooter, knocking both the shooter AND target to the ground. The force of the so-called "manstopper" .45ACP bullet is, in reality, comparable to the force imparted by a 1 kg (2.2 pound) mass dropped from a height of 3.47 m (11.4 feet) onto a surface.[16] Such a force is simply incapable of arresting a running target's forward momentum. In addition, bullets are designed to penetrate instead of strike a blunt force blow, because, in penetrating, more severe tissue damage is done. A bullet with sufficient energy to knock down an assailant, such as a high-speed rifle bullet, would be more likely to instead pass straight through, while not transferring the full energy (in fact only a very small percentage of the full energy) of the bullet to the victim.

The "knockback" effect is however commonly "seen" in real-life shootings, and can be explained by physiological and psychological means. Humans encountering a physical hit, be it a punch or a bullet, are conditioned to absorb the blow by moving in the same direction as the force. The physical effect against a non-penetrating weapon is to reduce the force felt by the blow, and in addition, retreating from an attack increases the distance such an attack must cover, which in the case of non-projectile weapons such as fists or a knife, places the target out of range of further attack. In addition, there is thought that Western civilization movies may have conditioned humans watching them to recoil, buckle, or fall backward when hit by a bullet, because that is the action taken by characters they have "seen" on TV or movies react when shot.

Although knockback is not possible with a handgun bullet, it can be an actual effect occurring in reaction to being hit by a massive slug, such as a rubber bullet or sandbag fired from a shotgun. The dynamics of a slug round are quite different than penetrating bullets; the projectile is here designed NOT to penetrate but instead to strike a hard, blunt force blow, and as the power of a shotgun cartridge is greater than practically any production handgun cartridge, the force imparted is comparable to a hard punch and is capable, by sheer physics, of doubling up, hence knocking down, someone.


[edit] One-shot stop
This hypothesis, promoted by Evan P. Marshall, is based solely on statistics, intended to be used as a unit of measurement and not as a tactical philosophy, as mistakenly believed by some. It considers the history of shooting incidents for a given factory ammunition load, and compiles the percentage of "one-shot-stops" achieved with each specific ammunition load. That percentage is then intended to be used with other information to help predict the effectiveness of that load getting a "one-shot-stop." For example, if an ammunition load is used in 10 torso shootings, incapacitating all but two with one shot, the "one-shot-stop" percentage for the total sample would be 80%.

Some argue that this hypothesis ignores any inherent selection bias. For example, high-velocity 9 mm hollow point rounds appear to have the highest percentage of one-shot stops. Rather than identifying this as an inherent property of the firearm/bullet combination, the situations where these have occurred need to be considered. The 9 mm has been the predominantly-used caliber of many police departments, so many of these one-shot-stops were probably made by well-trained police officers, where accurate placement would be a contributory factor. However, Marshall's database of "one-shot-stops" does include shootings from law enforcement agencies, private citizens, and criminals alike.

Critics of this theory point out that bullet placement is a very significant factor, but is only generally used in such one-shot-stop calculations, covering shots to the torso.

Some CCW holders in the United States have elected since 2006 to switch from carrying hollow-point bullets and especially 10 mm caliber weapons with perceived higher one-shot stopping power to instead favor carrying smaller caliber weapons after the conviction of retired school teacher Harold Fish in Arizona for second degree murder during a self-defense shooting. His conviction for killing a homeless man with a history of mental instability who attacked him while hiking on a remote trail was obtained through a jury trial by stressing Fish overreacted through choosing to use the increased stopping power of 10 mm hollow point bullets. State law in Arizona has subsequently been changed, such that the state now has the burden to prove that a self defense shooting was not in self defense, whereas the burden previously before the Fish incident was that the shooter on trial had to prove that the shooting was in fact done in self defense. Meanwhile, many CCW holders have elected to switch to carrying handguns loaded with FMJ bullets in calibers smaller than 10 mm. A choice often advocated for selecting the correct stopping power in CCW training classes is to select to use the exact same type of bullets (FMJ or hollow point), in the exact same caliber that are used by the local police, to avoid being accused of overreacting during any self defense post-incident trial.[17][18]


[edit] Big Hole School
This school of thought says that the bigger the hole in the target the higher the rate of bleed-out and thus the higher the rate of the "magical" one shot kill. In this theory, the bullet does not pass entirely through the body so that it incorporates the energy transfer and the overpenetration ideals. The people that like this theory cite the .40 S&W round to be the best bet, arguing that it has a better ballistic profile than the .45, with more stopping power than a 9x19mm Parabellum.

The theory centers on the "permanent cavitation" element of a handgun wound; a big hole damages more tissue. It is therefore valid to a point, but penetration is also important, as a large bullet that doesn't penetrate will be less likely to strike vital blood vessels and blood-carrying organs such as the heart and liver, while a smaller bullet that penetrates deep enough to strike these organs or vessels will cause faster bleed-out through a smaller hole. The ideal may therefore be a combination; a large bullet that penetrates deeply, which can be achieved with a larger, slower non-expanding bullet, or a smaller, faster expanding bullet such as a hollow point.


[edit] Other Contributing Factors
As it has been touched on previously, drug and/or alcohol levels within the body, body mass index, mental illness, motivation levels, body part strike (i.e. "armpit hold") all these things and more contribute to the concept of what round will possess true stopping power during which situation. .....full article - Credit given for article/All text is available under the terms of the GNU Free Documentation License. (See Copyrights for details.)
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