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Stopping power



 
 
Stopping power is a colloquial term used to describe the ability of a firearm
Firearm

A firearm is a tool that projects either single or multiple projectiles at high velocity through a controlled explosion. The firing is achieved by the gases produced through rapid, confined combustion of a propellant....
 or other weapon to cause a penetrating ballistic injury to a target human or animal, an injury sufficient to incapacitate the target where it stands.

The term is not a euphemism
Euphemism

A euphemism is a substitution of an agreeable or less offensive expression in place of one that may offend or suggest something unpleasant to the listener, or in the case of #Doublespeak, to make it less troublesome for the speaker....
 for lethality
Lethality

Lethality is a term designating the ability of a weapon to kill. Most often this term is used when referring to chemical weapons, biological weapons, or their chemical components....
. It refers only to a weapon's ability to incapacitate quickly, regardless of whether death ultimately results. Some theories of stopping power involve concepts such as "energy transfer" and "hydrostatic shock
Hydrostatic shock

The term hydrostatic shock describes the theory that a penetrating projectile produces remote wounding and incapacitating effects in living targets, in addition to local effects in tissue caused by direct impact, through a hydraulic effect in liquid filled tissues....
", although there is disagreement regarding the importance of these effects.

Stopping power is related to the physical properties of the bullet and the effects it has on its target, but the issue is complicated and not easily studied.






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Encyclopedia


Stopping power is a colloquial term used to describe the ability of a firearm
Firearm

A firearm is a tool that projects either single or multiple projectiles at high velocity through a controlled explosion. The firing is achieved by the gases produced through rapid, confined combustion of a propellant....
 or other weapon to cause a penetrating ballistic injury to a target human or animal, an injury sufficient to incapacitate the target where it stands.

The term is not a euphemism
Euphemism

A euphemism is a substitution of an agreeable or less offensive expression in place of one that may offend or suggest something unpleasant to the listener, or in the case of #Doublespeak, to make it less troublesome for the speaker....
 for lethality
Lethality

Lethality is a term designating the ability of a weapon to kill. Most often this term is used when referring to chemical weapons, biological weapons, or their chemical components....
. It refers only to a weapon's ability to incapacitate quickly, regardless of whether death ultimately results. Some theories of stopping power involve concepts such as "energy transfer" and "hydrostatic shock
Hydrostatic shock

The term hydrostatic shock describes the theory that a penetrating projectile produces remote wounding and incapacitating effects in living targets, in addition to local effects in tissue caused by direct impact, through a hydraulic effect in liquid filled tissues....
", although there is disagreement regarding the importance of these effects.

Stopping power is related to the physical properties of the bullet and the effects it has on its target, but the issue is complicated and not easily studied. Critics contend that the importance of "one-shot stop" statistics is overstated, pointing out that most gun encounters do not involve a "shoot once and see how the target reacts" situation.

Stopping is usually caused not by the force of the bullet (especially in the case of handgun
Handgun

A handgun is a firearm designed to be held and operated by one hand, with the other hand optionally supporting the shooting hand. This characteristic differentiates handguns as a general class of firearms from their larger counterparts: long guns such as rifles and shotguns , mounted weapons such as machine guns and autocannons, and l...
 and rifle
Rifle

A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls....
 bullets), but by the damaging effects of the bullet which are typically a loss of blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
, and with it, blood pressure
Blood pressure

Blood pressure is the pressure exerted by circulating blood on the walls of blood vessels, and constitutes one of the principal vital signs. The pressure of the circulating blood decreases as it moves away from the heart through artery and capillary, and toward the heart through veins....
. More immediate effects can result when a bullet damages the central nervous system
Central nervous system

The central nervous system is the part of the nervous system that functions to coordinate the activity of all parts of the bodies of multicellular organisms....
 such as the spine or brain. In response to addressing stopping power issues, the Mozambique Drill
Mozambique Drill

The Mozambique Drill is a firearms technique. It instructs the shooter to place a double-tap in the center of mass, followed by a deliberate target assessment, then a carefully aimed, follow-up, head shot....
 was developed, to maximize the likelihood of a quick incapacitation of an attacker.

A manstopper is a generic term used to describe almost any combination of firearm
Firearm

A firearm is a tool that projects either single or multiple projectiles at high velocity through a controlled explosion. The firing is achieved by the gases produced through rapid, confined combustion of a propellant....
 and ammunition
Ammunition

Ammunition, often referred to as ammo, is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery....
 that can reliably be expected to incapacitate, or "stop" a human target immediately. For example, the .45 ACP
.45 ACP

The .45 ACP , also known as the .45 Auto by C.I.P., is a rim pistol Cartridge designed by John Browning in 1904, for use in his prototype Colt Firearms semi-automatic .45 pistol and eventually the M1911 Colt pistol pistol adopted by the United States Army in 1911....
 pistol round and the .357 Magnum
.357 Magnum

The .357 S&W Magnum, or simply .357 Magnum, is a revolver Cartridge created by Elmer Keith, Phillip B. Sharpe, Colonel D. B. Wesson of firearms manufacturer Smith & Wesson, and Winchester....
 revolver round have a firm reputation as "manstoppers". Historically, one type of ammunition has had the specific tradename "Manstopper". Officially known as the Mk III cartridge
.455 Webley

.455 Webley is a UK handgun cartridge, most commonly used in the Webley Revolver Marks I through VI.The .455 cartridge was a service revolver cartridge, featuring a rimmed cartridge firing a .45 bullet at the relatively low velocity of 650 ft/s ....
, these were made to suit the British Webley .455 service revolver
Webley Revolver

The Webley Revolver was, in various Mark , the standard issue service pistol for the armed forces of the United Kingdom, the British Empire, and the Commonwealth of Nations from 1887 until 1963....
 in the early 20th century. The ammunition used a 220 grain
Grain (measure)

In many cultures, a grain is a Physical unit of measurement of mass that is based upon the mass of a single seed of a typical cereal. Historically, in Europe, the average masses of wheat and barley grain were used to define units of mass....
 cylindrical bullet with hemispherical depressions at both ends. The front acted as a hollow point
Hollow point bullet

A hollow point is a bullet that has a pit or hollowed out shape in its tip, generally intended to cause the bullet to expand upon entering a target in order to decrease penetration and disrupt more tissue as it travels through the target....
 deforming on impact while the base opened to seal the round in the barrel. It was introduced in 1898 for use against "savage
Savage

Savage may refer to:Places* Savage, Maryland* Savage, Minnesota* Lower Savage Islands, Nunavut, Canada* Middle Savage Islands, Nunavut, Canada...
s," but fell quickly from favour due to concerns of breaching the Hague Convention's
Hague Conventions (1899 and 1907)

The Hague Conventions were international treaty negotiated at the First and Second Peace Conferences at The Hague, Netherlands in 1899 and 1907, respectively, and were, along with the Geneva Conventions, among the first formal statements of the laws of war and war crimes in the nascent body of secular international law....
 international laws on military ammunition, and was replaced in 1900 by re-issued Mk II pointed-bullet ammunition.

Some sporting arms are also referred to as "stoppers" or "stopping rifles". These powerful arms are often used by game
Game (food)

Game is any animal hunting for food or not normally Domestication . Game animals are also hunted for sport.The type and range of animals hunted for food varies in different parts of the world....
 hunters (or their guides) for stopping a suddenly-charging creature, like a buffalo or an elephant
Elephant

Elephants are large land mammals of the order Proboscidea and the family Elephantidae. There are three living species: the African Bush Elephant, the African Forest Elephant and the Asian Elephant ....
.

History

The concept of "stopping power" appeared in the late 19th Century when colonial troops (American
United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
 in the Philippines
Philippines

The Philippines, officially known as the Republic of the Philippines, is a country in Southeast Asia with Manila as its capital city. It comprises 7,107 islands in the western Pacific Ocean....
, British
British Empire

The British Empire comprised the dominions, Crown colony, protectorates, League of Nations mandate, and other Dependent territory ruled or administered by the United Kingdom , that had originated with the overseas colonies and trading posts established by England in the late 16th and early 17th centuries....
 in New Zealand
New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous Islands of New Zealand, most notably Stewart Island/Rakiura and the Chatham Islands....
) engaging in close action with native tribesmen found that their pistols were not able to stop charging warrior
Warrior

According to the Random House Dictionary, the term warrior has two meanings. The first Literal and figurative language use refers to "a person engaged or experienced in warfare." The second Literal and figurative language use refers to "a person who shows or has shown great vigor, courage, or aggressiveness, as in politics or athletics...
s. This led to larger caliber weapons (such as the .45 ACP
.45 ACP

The .45 ACP , also known as the .45 Auto by C.I.P., is a rim pistol Cartridge designed by John Browning in 1904, for use in his prototype Colt Firearms semi-automatic .45 pistol and eventually the M1911 Colt pistol pistol adopted by the United States Army in 1911....
) being developed to stop opponents with a single round. (See Knockback)

Dynamics of bullets

A bullet
Bullet

A bullet is a hard projectile propelled by a firearm, Sling , or air gun and is normally made from metal. A bullet does not contain explosives, but damages the intended target by tissue or mechanical disruption through impact or penetration....
 will destroy or damage any tissues which it penetrates, creating a wound channel. It will also cause nearby tissue to stretch and expand as it passes through tissue. These two effects are typically referred to as permanent cavitation (the hole left by the bullet) and temporary cavitation (the tissue displaced as the bullet passed).

The degree to which permanent and temporary cavitation occur is dependent on the weight, diameter
Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle....
, material, design and velocity
Velocity

In physics, velocity is defined as the Derivative of Position vector. It is a vector physical quantity; both speed and direction are required to define it....
 of the bullet. This is because bullets crush tissue, and do not cut it. A bullet constructed with a half diameter ogive
Ogive

An ogive is a curved shape, figure, or feature....
 designed meplat
Meplat

Meplat, from a French term for a flat surface, is the technical term for the tip or nose of a bullet. The shape of the meplat is important when determining how the bullet will move through the air....
 and hard, solid copper
Copper

Copper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity....
 alloy material will crush only the tissue directly in front of the bullet. This type of bullet (monolithic-solid rifle bullet) is conducive to cause more temporary cavitation as the tissue flows around the bullet, causing a deep and narrow wound channel. A bullet constructed with a two diameter, hollow point ogive
Ogive

An ogive is a curved shape, figure, or feature....
 designed meplat and low antimony
Antimony

Antimony is a chemical element with the symbol Sb and atomic number 51. A metalloid, antimony has four allotropy forms. The stable form of antimony is a blue-white metalloid....
 lead
Lead

Lead is a main-group Chemical element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metal ....
 core with a thin gilding metal jacket material will crush tissue in front and to the sides as the bullet expands. Due to the energy expended in bullet expansion, velocity is lost more quickly. This type of bullet (hollow-point hand gun bullet) is conducive to causing more permanent cavitation as the tissue is crushed and accelerated into other tissues by the bullet, causing a shorter and more voluminous wound channel.

Bullets are constructed to behave in different ways, depending on the intended target. Different bullets are constructed variously to: not expand upon impact, expand upon impact at high velocity, expand upon impact, expand across a broad range of velocities, expand upon impact at low velocity, tumble upon impact, fragment upon impact, or disintegrate upon impact.

To control the expansion of a bullet, meplat
Meplat

Meplat, from a French term for a flat surface, is the technical term for the tip or nose of a bullet. The shape of the meplat is important when determining how the bullet will move through the air....
 design and materials are engineered. The meplat designs are: flat; round to pointed depending on the ogive; hollow pointed which can be large in diameter and shallow or narrow in diameter and deep and truncated which is a long narrow punched hole in the end of a monolithic-solid type bullet. The materials used to make bullets are: pure lead; alloyed lead for hardness; gilding metal
Gilding metal

Gilding metal is a copper alloy, comprising 95% copper and 5% zinc. Technically, it is a form of brass.Gilding metal is used for various purposes, including the cartridges of bullets, driving bands on some artillery shells, as well as enamelled badges and other jewellery....
 jacket which is a copper alloy of nickel
Nickel

Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge....
 and zinc
Zinc

Zinc is a metallic chemical element with the symbol Zn and atomic number 30. It is a first-row transition metal of the group 12 element of the periodic table....
 to promote higher velocities; pure copper; copper alloy of bronze
Bronze

Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive, but sometimes with other chemical element such as phosphorus, manganese, aluminium, or silicon....
 and tungsten
Tungsten

Tungsten , also known as wolfram , is a chemical element that has the symbol W and atomic number 74.A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite....
 steel alloy inserts to promote weight.

Some bullets are constructed by bonding the lead core to the jacket to promote higher weight retention upon impact, causing a larger and deeper wound channel. Some bullets have a web in the center of the bullet to limit the expansion of the bullet while promoting penetration. Some bullets have dual cores to promote penetration.

Bullets that might be considered to have stopping power for dangerous large game animals are usually 11.63 mm (.458 caliber) and larger, including 12-gauge shotgun slugs. These bullets are monolithic-solids; full metal jacketed and tungsten steel insert. They are constructed to hold up during close range, high velocity impacts. These bullets are expected to impact and penetrate, and transfer energy to the surrounding tissues and vital organs through the entire length of a game animal’s body if need be.

Bullets with sufficient stopping power for humans are generally large caliber, 9.07 mm (.357 caliber
Caliber

The term caliber designates the inside diameter of a tube, the diameter of a solid wire or rod, or a measurement of the length of a gun relative to its diameter....
) handgun bullets of hollow point design. Pre-fragmented bullets such as Glaser Safety Slugs and Magsafe ammunition are designed to fragment into birdshot on impact with the target. This fragmentation is intended to create more trauma to the target, and also to reduce collateral damage caused from ricocheting or overpenetrating of the target and the surrounding environments such as walls.

Physical effects

Permanent and temporary cavitation cause very different biological effects. The effects of a permanent cavity are fairly obvious. A hole through the heart
Heart

The heart is a muscle organ in all vertebrates responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods....
 will cause loss of pumping efficiency, loss of blood, and eventual cardiac arrest
Cardiac arrest

A cardiac arrest, also known as cardiopulmonary arrest or circulatory arrest, is the abrupt cessation of normal circulation of the blood due to failure of the heart to contract effectively during Systole ....
. A hole through the brain
Brain

The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as cnidarian and echinoderm have a decentralized nervous system without a brain, while sponges lack any nervous system at all....
 can cause instant unconsciousness
Unconsciousness

Unconsciousness, more appropriately referred to as loss of consciousness or lack of consciousness, is a dramatic alteration of mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli....
 and will likely kill the recipient. A hole through an arm or leg which hits only muscle
MUSCLE

MUSCLE is public domain, multiple sequence alignment software for protein and nucleotide sequences.MUSCLE is integrated into UGENE bioinformatics tool as a plugin....
, however, will cause a great deal of pain but is unlikely to be fatal, unless one of the large blood vessels (femoral
Femoral

Femoral can refer to:* Femoral artery* Femoral vein* Femur* Femoral triangle* Femoral nerve...
 or brachial arteries, for example) is also severed in the process.

The effects of temporary cavitation are less well understood, due to a lack of a test material identical to living tissue. Studies on the effects of bullets typically are based on experiments using ballistic gelatin
Ballistic gelatin

Ballistic gelatin is a solution of gelatin powder in water. Ballistic gelatin closely simulates the density and viscosity of human and animal muscle tissue, and is used as a standardized medium for testing the terminal performance of firearms ammunition....
, in which temporary cavitation causes radial tears where the gelatin was stretched. Although such tears are visually engaging, some animal tissues, (other than bone or liver) are more elastic
Elasticity (physics)

In physics, elasticity is the physical property of a material when it deforms under stress , but returns to its original shape when the stress is removed....
 than gelatin . In most cases, temporary cavitation is unlikely to cause anything more than a slight bruise
Bruise

A bruise, also called a contusion, is an injury to biological tissue in which the capillary are damaged, allowing blood to seep into the surrounding tissue....
. Some speculation states that nerve bundles
Nerve

A nerve is an enclosed, cable-like bundle of Peripheral nervous system axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons....
 can be damaged by temporary cavitation, creating a stunning effect, but this has not been confirmed.

One exception to this is when a very powerful temporary cavity intersects with the spine
Vertebral column

In human anatomy, the vertebral column is a column of 24 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsum aspect of the torso, separated by spinal discs....
. In this case, the resulting blunt trauma
Physical trauma

Physical trauma refers to a body injury. A trauma patient is someone who has suffered serious and life-threatening physical injury with the potential for secondary complications such as Shock , respiratory failure and death....
 can slam the vertebrae together hard enough to either sever the spinal cord, or damage it enough to knock out, stun, or paralyze the target. For instance, in the shootout between eight FBI agents and two bank robbers on April 11, 1986 in Miami, Florida
Florida

Florida is a U.S. state located in the Southeastern United States of the United States, bordering Alabama to the northwest and Georgia to the northeast....
, (see FBI Miami shootout, 1986
FBI Miami shootout, 1986

The FBI Miami shootout was a gun battle that occurred on April 11, 1986 in Miami, Florida between multiple FBI agents and two heavily-armed and well-trained gunmen....
) Special Agent Gordon McNeill was struck in the neck by a high-velocity .223 bullet fired by Michael Platt. While the bullet did not directly contact the spine, and the wound incurred was not ultimately fatal, the temporary cavitation was sufficient to render SA McNeill paralyzed for several hours.

Temporary cavitation can also cause the tearing of tissues if a very large amount of force is involved. The tensile strength of muscle ranges roughly from 1 to 4 MPa (145 to 580 lbf/in²), and minimal damage will result if the pressure exerted by the temporary cavitation is below this . Gelatin and other less elastic media have much lower tensile strengths, thus they exhibit more damage after being struck with the same amount of force. At typical handgun velocities, bullets will create temporary cavities with much less than 1 MPa of pressure, and thus are incapable of causing damage to elastic tissues which they do not directly contact.

Core-locked rifle bullets that strike a major bone (such as a femur) can expend their entire energy into the surrounding tissue, causing it to take on a gelled consistency as the cellular structure is destroyed. The struck bone is commonly shattered at the point of impact.

High velocity fragmentation can also increase the effect of temporary cavitation. The fragments sheared from the bullet cause many small permanent cavities around the main entry point. The main mass of the bullet can then cause a truly massive amount of tearing as the perforated tissue is stretched.

Whether a person or animal will be incapacitated (i.e. 'stopped') when shot depends on a large number of factors including physical, physiological, and psychological effects.

Neurological effects

The only way to immediately incapacitate a person or other animal is to damage or disrupt their central nervous system
Central nervous system

The central nervous system is the part of the nervous system that functions to coordinate the activity of all parts of the bodies of multicellular organisms....
 (CNS) to the point of becoming paralyzed, losing consciousness, or dying. Bullets can achieve this directly or indirectly. If a bullet causes sufficient damage to the brain
Brain

The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as cnidarian and echinoderm have a decentralized nervous system without a brain, while sponges lack any nervous system at all....
 or spinal cord
Spinal cord

The spinal cord is a long, thin, tubular bundle of neuron and glia that extends from the brain. The brain and spinal cord together make up the central nervous system....
, immediate loss of consciousness or paralysis, respectively, can result. However, these targets are relatively small and mobile, making them extremely difficult to hit even under optimal circumstances.

Bullets can indirectly disrupt the CNS by damaging the cardiovascular system so that it can no longer provide enough oxygen to the brain to sustain consciousness. This can be the result of bleeding
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
 from a perforation of a large blood vessel or blood-bearing organ, or the result of damage to the lungs or airway. If blood flow is completely cut off from the brain, a human still has enough oxygenated blood in their brain for 10-15 seconds of willful action, though with rapidly decreasing effectiveness as the victim begins to lose consciousness.

Unless a bullet directly damages or disrupts the central nervous system, a person or animal will not be instantly and completely incapacitated by physiological damage. However, bullets can cause other disabling injuries that prevent specific actions (a person shot in the femur cannot walk) and the physiological pain response from severe injuries will temporarily disable most individuals.

A number of papers in the peer-reviewed journals suggest ballistic pressure wave effects on wounding and incapacitation, including remote neural effects. These papers are mainly concerned with velocities of rifle bullets, but the energy transfer and pressure waves produced are within the regime of pistol bullets.

Recent work by Courtney and Courtney provides compelling support for the role of a ballistic pressure wave in creating remote neural effects leading to incapacitation and injury.

This work builds upon the earlier works of Suneson et al. where the researchers implanted high-speed pressure transducers into the brain of pigs and demonstrated that a significant pressure wave reaches the brain of pigs shot in the thigh. These scientists observed neural damage in the brain caused by the distant effects of the ballistic pressure wave originating in the thigh.

The results of Suneson et al. were confirmed and expanded upon by a later experiment in dogs which "confirmed that distant effect exists in the central nervous system after a high-energy missile impact to an extremity. A high-frequency oscillating pressure wave with large amplitude and short duration was found in the brain after the extremity impact of a high-energy missile . . ." Wang et al. observed significant damage in both the hypothalamus and hippocampus regions of the brain due to remote effects of the ballistic pressure wave.

Psychological effects

Emotional shock, terror, or surprise can cause a person to faint
Syncope (medicine)

Syncope is the medical term for fainting, a sudden, usually temporary, loss of consciousness generally caused by insufficient oxygen in the brain either through cerebral hypoxia or through hypotension, but possibly for other reasons....
, surrender, or flee when shot or shot at. Emotional fainting is the likely reason for most "one-shot stops", and not an intrinsic effectiveness quality of any firearm or bullet; there are many documented instances where suspects have instantly dropped unconscious when the bullet only hit an extremity, or even completely missed. Additionally, the muzzle blast and flash from many firearms are substantial and can cause disorientation, dazzling, and stunning effects. Flashbangs (stun grenades) and other less-lethal "distraction devices" rely exclusively on these effects.

Pain
Pain

Pain, in the sense of physical pain, is a typical sensory experience that may be described as the unpleasant awareness of a noxious stimulus or bodily harm....
 is another psychological factor, and can be enough to dissuade a person from continuing their actions.

Temporary cavitation can emphasize the impact of a bullet, since the resulting tissue compression is identical to simple blunt force trauma. It's easier for someone to feel when they have been shot if there is considerable temporary cavitation, and this can contribute to either psychological factor of incapacitation.

However, if a person is sufficiently enraged
Rage (emotion)

Rage, in psychiatry, is a mental state that is one extreme of the intensity spectrum of anger. When a person experiences rage it usually lasts until a threat is removed or the person under rage is maimed/injured or killed....
, determined, or intoxicated
Intoxication

Intoxication is the state of being affected by one or more Psychoactive drug. It can also refer to the effects caused by the ingestion of poison or by the overconsumption of normally harmless substances....
 they can simply shrug off the psychological effects of being shot. Therefore, such effects are not as reliable as physiological effects at stopping people. Animals will not faint or surrender if injured, though they may become frightened by the loud noise and pain of being shot, so psychological mechanisms are generally less effective against non-humans.

Industry penetration requirements

According to Dr. Martin Fackler
Martin Fackler

Martin L. Fackler was a battlefield surgery, but is better known in the field of terminal ballistics, an area requiring expertise in non medical topics such as mechanics, materials science, and structural/failure analysis....
 and the International Wound Ballistics Association (IWBA), between 12.5 and 14 inches (318 and 356 mm) of penetration in calibrated tissue simulant is optimal performance for a bullet which is meant to be used defensively, against a human adversary. They also believe that penetration is one of the most important factors when choosing a bullet (and that the number one factor is shot placement). If the bullet penetrates less than their guidelines, it is inadequate, and if it penetrates more, it is still satisfactory though not optimal. The FBI's penetration requirement is very similar at 12 to 18 inches (305 to 457 mm).

A penetration depth of 12.5 to 14 inches (318 and 356 mm) may seem excessive, but a bullet sheds velocity — and crushes a narrower hole — as it penetrates deeper, while losing velocity, so the bullet might be crushing a very small amount of tissue (simulating an "ice pick" injury) during its last two or three inches of travel, giving only between 9.5 and 12 inches of effective wide-area penetration. Also, skin is elastic and tough enough to cause a bullet to be retained in the body, even if the bullet had a relatively high velocity when it hit the skin. About 250 ft/s (76 m/s) velocity is required for an expanded hollow point bullet to puncture skin 50% of the time.

The IWBA's and FBI's penetration guidelines are to ensure that the bullet can reach a vital structure from most angles, while retaining enough velocity to generate a large diameter hole through tissue. An extreme example where penetration would be important is if the bullet first had to enter and then exit an outstretched arm before impacting the torso. A bullet with low penetration might embed itself in the arm whereas a higher penetrating bullet would penetrate the arm then enter the thorax where it would have a chance of hitting a vital organ.

Overpenetration

Overpenetration is often emphasized by those that prefer shallow-penetrating "rapid energy transfer" bullets. Tests have shown that human skin, on the entry side, can resist penetration as much as 2" (5 cm) of muscle, and skin on the exit side can be the equivalent of up to 4 in (10 cm). A bullet would need to penetrate greater than approximately 15 inches (38 cm) of tissue simulant to have a chance to completely perforate a 9" (23 cm) thick torso, and would need to penetrate more than 17 inches (43 cm) to actually pose a serious threat to people downrange.

Even if the bullet does completely penetrate a person, it will have a very reduced velocity and probably will no longer be ballistically stable. Missing the intended target altogether, hence leaving a full velocity bullet to harm whatever is in its path, is a much greater threat.

A hit on a less dense peripheral body area, such as a limb, does present a more serious risk of overpenetration however. Penetration of walls and other cover is also a consideration for police and urban use.

According to NYPD SOP-9 (Standard Operating Procedure #9) data, in the year 2000, only 9% of shots fired by officers engaged in gunfights actually hit perpetrators at which they were fired. In the same year, there were a total of 129 "shooting incidents" (including non-gunfights, such as officers firing at aggressive dogs, unarmed or fleeing perpetrators, etc.), 471 total shots fired by officers, 367 shots fired at perpetrators, and 58 total hits on perpetrators by police. So, when non-gunfight shooting data is added, the rate at which police hit what they aim at in real life situations is typically only 15.8%. By either measure, the vast majority of bullets were not stopped by hitting perpetrators, but ultimately encountered some other object. The propensity of these "stray" bullets to pass through windows, walls, car doors, etc. and possibly injure bystanders is a concern, and falls into the overall risk/benefit calculation when considering how much penetration is enough.

A study carried out by the FBI found that the .223 Remington
.223 Remington

The .223 Remington is a sporting cartridge with almost the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a diameter, jacketed bullet, with weights ranging from 40 up to , though the most common loading by far is ....
 from a rifle had a smaller chance of overpenetration than the 9 mm Luger handgun round.

Other hypotheses of stopping power

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

Energy transfer

The energy transfer hypotheses states that the more energy
Energy

In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
 that is transferred to the target, the greater the destructive potential.

In ballistics, energy is a function of mass and the square of velocity. Generally speaking, it is the intention of the shooter to deliver an adequate amount of energy to the target via the projectile/s. Projectiles such as rifle bullets, high velocity handgun bullets and shotgun slugs can over-penetrate. Projectiles such as handgun bullets and shot can under-penetrate. Projectiles that reach the target with too low a velocity or bird shot may not penetrate at all. All the above conditions affect energy transfer.

Over-penetration is detrimental to stopping power in regards to energy. This is because a bullet that passes through the target does not transfer all of its energy to the target. Despite decreased tissue damage due to loss of transferred energy on an over-penetrating shot, the resulting exit wound would cause increased blood loss and therefore a decrease in blood pressure in the victim. This effect on both persons and game animals is likely to be incapacitating over the length of the entire shooting event.

Under-penetration is also detrimental to stopping power. Projectile/s that do not transfer enough energy to the target may fail to create a fatal wound cavity. Also vital organs may not be reached, thereby limiting the amount of tissue damage, blood loss, and/or loss of blood pressure.

Non-penetration of projectile/s may only deliver enough energy to create bruising, punctures and or blunt force trauma
Blunt force trauma

Blunt force trauma may refer to:* Blunt trauma, a medical term referring to a type of physical trauma* Blunt Force Trauma , a band from Austin, Texas...
. All of which may result in internal injury solely through the force of the impact but not stop the target.

As mentioned above, there are many factors that affect "stopping power." Within this theory energy transfer is related to destructive potential; however, the importance of energy transfer in determining the stopping power of projectiles (when compared to other factors like location of the wound and wound cavity size) is a controversial topic.

It is a general principal of physics that the force exerted by a projectile upon tissue is equal to the bullet's local rate of energy loss, dEk/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).

This ‘energy transfer” theory is frequently referred to by Kennedy assassination theories
Kennedy assassination theories

There are many conspiracy theory regarding the John F. Kennedy assassination on 22 November, 1963; many arose soon after John F. Kennedy death and continue to be promulgated today....
. These theorists cite the Zapruder film
Zapruder film

The Zapruder film is a silent Standard 8 mm film color home movies of the presidential motorcade of John F. Kennedy through Dealey Plaza in Dallas, Texas, on November 22, 1963, filmed by a private citizen named Abraham Zapruder....
, as evidence that that shot that killed President John F. Kennedy
John F. Kennedy

John Fitzgerald "Jack" Kennedy , often referred to by his initials JFK, was the List of Presidents of the United States President of the United States, serving from 1961 until John F....
 must have been fired from in front of the limousine rather than from behind; which the Zapruder film shows Kennedy's head recoiling backwards from a shot. Lee Harvey Oswald
Lee Harvey Oswald

Lee Harvey Oswald was, according to three United States government investigations, the John F. Kennedy assassination of President of the United States John F....
 was claimed to have fired from the Texas School Book Depository
Texas School Book Depository

The Texas School Book Depository is the former name of a seven-floor building facing Dealey Plaza in Dallas, Texas . Located on the northwest corner of Elm and North Houston Streets, at the western end of downtown Dallas, its address is 411 Elm Street, Dallas, TX 75202-3317....
, and thus The Zapruder film implies a second assassin as inferred by Kennedy assassination theorists. However, it was recently shown to a large television audience by Penn and Teller on May 9, 2005 on their Showtime
Showtime

Showtime is a Pay TV brand used by a number of channels and platforms around the world, but primarily refers to a group of channels in the United States....
 network program, Bullshit!
Bullshit!

Penn & Teller: Bullshit! is a United States Documentary film television series that has been on the air since 2003 on the premium cable channel Showtime on Thursday nights at 10 pm EST....
, that when a simplified model of a brain inside a skull, composed of a melon
Melon

Melon is a name given to various members of the Cucurbitaceae family with fleshy fruit. Melon can refer to either the plant or the fruit, which is a Epigynous berry....
 wrapped with strapping tape, is shot in a similar fashion, the melon recoils backwards, towards the gun. This observed, non-scientific experiment shows the actual transfer of energy from a bullet passing through a complex object producing a backwards and unexpected result.

The theory of energy transfer can be observed in other theories.

Hydrostatic shock

Hydrostatic shock
Hydrostatic shock

The term hydrostatic shock describes the theory that a penetrating projectile produces remote wounding and incapacitating effects in living targets, in addition to local effects in tissue caused by direct impact, through a hydraulic effect in liquid filled tissues....
 is a theory of terminal ballistics
Terminal ballistics

Terminal ballistics, a sub-field of ballistics, is the study of the behavior of a projectile when it hits its target. It is often referred to as stopping power when dealing with human or other living targets....
 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.

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
.38 Long Colt

The .38 Long Colt is a Cartridge introduced by Colt's Manufacturing Company in 1875. It is slightly more potent than its predecessor, the .38 Short Colt, or .38 SC....
 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 M1911A1 pistol and the British adopted the .455 Webley
.455 Webley

.455 Webley is a UK handgun cartridge, most commonly used in the Webley Revolver Marks I through VI.The .455 cartridge was a service revolver cartridge, featuring a rimmed cartridge firing a .45 bullet at the relatively low velocity of 650 ft/s ....
 caliber cartridge in the Webley Revolver
Webley Revolver

The Webley Revolver was, in various Mark , the standard issue service pistol for the armed forces of the United Kingdom, the British Empire, and the Commonwealth of Nations from 1887 until 1963....
. 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
.44 Magnum

The .44 Remington Magnum, or simply .44 Magnum, is a large-bore Cartridge originally designed for revolvers. After introduction, it was quickly adopted for carbines and rifles....
, the effect of knockback from a handgun and indeed most personal weapons is largely a myth. The momentum
Momentum

In classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section Momentum#Modern definitions of momentum on this page....
 of the so-called "manstopper" .45 ACP
.45 ACP

The .45 ACP , also known as the .45 Auto by C.I.P., is a rim pistol Cartridge designed by John Browning in 1904, for use in his prototype Colt Firearms semi-automatic .45 pistol and eventually the M1911 Colt pistol pistol adopted by the United States Army in 1911....
 bullet is approximately the momentum [28ft·lbm/s (3.9 kg·m/s)] of a 1 pound (0.45 kilogram) mass dropped from a height of 14 feet (4.3 meters). It should be noted that momentum is very different from kinetic energy
Kinetic energy

The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the mechanical work needed to accelerate a body of a given mass from rest to its current velocity....
; an equivalent kinetic energy [855ft·lbf (1159 J)]of a typical .45 ACP bullet is that of a 60 pound (27 kilogram) mass dropped from a height of 14 feet (4.3 meters). 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 a theoretical sociological explanation, that in modern civilization, with far greater separation by most individuals from violence, hunting, and combat, normal individuals may simply recoil, buckle, or fall backward when hit by a bullet, even when in pure physiological terms they are perfectly capable of continuing to charge.

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
Shotgun

A shotgun is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called lead shot, or a solid projectile called a shotgun slug....
. 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.

One-shot stop

This hypothesis, promoted by Evan P. Marshall, is based on statistical analysis of actual shooting incidents from various reporting sources (typically police agencies). It is 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
Selection bias

Selection bias is a distortion of evidence or data that arises from the way that the data are collected. It is sometimes referred to as the selection effect....
. For example, high-velocity 9 mm hollow point
Hollow point bullet

A hollow point is a bullet that has a pit or hollowed out shape in its tip, generally intended to cause the bullet to expand upon entering a target in order to decrease penetration and disrupt more tissue as it travels through the target....
 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.

Since 2006, after the conviction of retired school teacher Harold Fish in Arizona for second degree murder during a self-defense shooting, some CCW
Carrying concealed weapon

In the United States, carrying a concealed weapon is the legal authorization for private citizens to carry a handgun or other weapons in public in a concealed manner, either on the person or in close proximity to the person....
 holders in the United States have elected to switch from carrying hollow-point bullets, and especially 10mm Auto caliber weapons with perceived higher one-shot stopping power, to carrying smaller caliber weapons. Fish's 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 that Fish overreacted, through choosing to use the increased stopping power of 10 mm hollow point
Hollow point bullet

A hollow point is a bullet that has a pit or hollowed out shape in its tip, generally intended to cause the bullet to expand upon entering a target in order to decrease penetration and disrupt more tissue as it travels through the target....
 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.

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 aforementioned "one shot kill". According to this theory, as the bullet does not pass entirely through the body, it incorporates the energy transfer and the overpenetration ideals. The people that support this theory cite the .40 S&W round, arguing that it has a better ballistic profile than the .45, and 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. It is important to note however, that in the extreme a heavier bullet (which preserves momentum greater than a lighter bullet of the same caliber) may "overpenetrate", passing completely through the target without expending all of its kinetic energy in the target.

Other contributing factors

As mentioned earlier, there are many factors, such as drug and/or alcohol levels within the body, body mass index
Body mass index

The body mass index , or Quetelet index, is a statistical measurement which compares a person's weight and height. Though it does not actually measure the Body fat percentage, it is a useful tool to estimate a healthy body weight based on how tall a person is....
, mental illness
Mental illness

A mental disorder or mental illness is a psychological or behavioral pattern that occurs in an individual and is thought to cause distress or disability that is not expected as part of normal development or culture....
, motivation levels, body part strike (i.e. "armpit hold") which may determine which round will possess true stopping power during any given situation.

See also

  • Expanding bullet
  • Terminal ballistics
    Terminal ballistics

    Terminal ballistics, a sub-field of ballistics, is the study of the behavior of a projectile when it hits its target. It is often referred to as stopping power when dealing with human or other living targets....
  • Hydrostatic shock
    Hydrostatic shock

    The term hydrostatic shock describes the theory that a penetrating projectile produces remote wounding and incapacitating effects in living targets, in addition to local effects in tissue caused by direct impact, through a hydraulic effect in liquid filled tissues....


External links

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