Terminal ballistics
Terminal ballistics, a sub-field of ballistics
Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...

, is the study of the behavior of a projectile
A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....

 when it hits its target. It is often referred to as stopping power
Stopping power
Stopping power is a colloquial term used to describe the ability of a firearm or other weapon to cause a penetrating ballistic injury to a target, human or animal, sufficient to incapacitate the target where it stands....

 when dealing with human or other living targets. Terminal ballistics is relevant both for small caliber projectiles as well as for large caliber projectiles (fired from artillery
Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...

). The study of extremely high velocity impacts is still very new and is as yet mostly applied to spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....


Classes of bullet

There are three basic classes of bullet:
  • those designed for maximum accuracy at varying ranges
  • those designed to maximize damage to a target by penetrating as deeply as possible
  • those designed to maximize damage to a target by deforming to control the depth to which the bullet penetrates.

The third class may limit penetration by expanding or fragmenting.

Target shooting

For short range target shooting on ranges up to 50 meters (55 yd) aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...

 is relatively unimportant and velocities are low. As long as the bullet is balanced so it does not tumble, the aerodynamics are unimportant. For shooting at paper targets, the best bullet is one that will punch a perfect hole through the target. These bullets are called wadcutter
A wadcutter is a special-purpose bullet specially designed for shooting paper targets, usually at close range and at subsonic velocities typically under 800 ft/s . They are often used in handgun and airgun competitions...

s, and they have a very flat front, often with a relatively sharp edge along the perimeter. The flat front punches out a large hole in the paper, close to if not equal to the full diameter of the bullet. This allows for easy, unambiguous scoring of the target. Since cutting the edge of a target ring will result in scoring the higher score, fractions of an inch are important. Magazine-fed pistols may not reliably feed wadcutters because of the angular shape. To address this, the semiwadcutter
A semiwadcutter or SWC is a type of all-purpose bullet commonly used in revolvers. The SWC combines features of the wadcutter target bullet and traditional round nosed revolver bullets, and is used in both revolver and pistol cartridges for hunting, target shooting, and plinking...

 is used. The semiwadcutter consists of a conical section that comes to a smaller flat, and a thin sharp shoulder at the base of the cone. The flat point punches a clean hole, and the shoulder opens the hole up cleanly. For steel targets, the concern is to provide enough force to knock over the target while minimizing the damage to the target. A soft lead bullet, or a jacketed hollow-point bullet or soft-point bullet will flatten out on impact (if the velocity at impact is sufficient to make it deform), spreading the impact over a larger area of the target, allowing more total force to be applied without damaging the steel target.

There are also specialized bullets designed specifically for use in long range precision target shooting with high-powered rifles; the designs vary somewhat from manufacturer to manufacturer, but all are based on the MatchKing bullets introduced by the Sierra Bullet Company
Sierra Bullets
Founded in 1947 in California, Sierra Bullets is an American manufacturer of bullets intended for firearms. Based in Sedalia, Missouri since 1990, Sierra manufactures a very wide range of bullets for both rifles and pistols. Sierra bullets are used for precision target shooting, hunting and defense...

 around 1963. Based on research done in the 1950s by the U.S. Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...

, in which it was discovered that bullets are more stable in flight for longer distances and more resistant to crosswinds if the center of gravity is somewhat to the rear of the center of pressure, the MatchKing bullet (which is still in wide use and holds many records) is a hollow point design with a tiny aperture in the jacket at the point of the bullet and a hollow air space under the point of the bullet, where previous conventional bullets had had a lead core that went all the way up to the point. Other designs from other manufacturers may be anything from close copies of the MatchKing design to hollow point bullets with a deep, wide cavity containing a long, slender, pointed plastic or aluminum plug. In all these cases, the bullet is designed to have its center of gravity to the rear of its center of pressure. MatchKing-type hollow point bullets, as contrasted with hollow point bullets intended for hunting or police use, are not designed to flatten out on impact; this makes them a relatively poor choice for hunting, as they tend to perform erratically and unpredictably upon entering an animal's body—they may tumble, or break apart, though most often they punch straight through making a narrow wound that usually does not cause death quickly. The U.S. military
United States armed forces
The United States Armed Forces are the military forces of the United States. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard.The United States has a strong tradition of civilian control of the military...

 now issues ammunition to sniper
A sniper is a marksman who shoots targets from concealed positions or distances exceeding the capabilities of regular personnel. Snipers typically have specialized training and distinct high-precision rifles....

s that use bullets of this type. In 7.62×51 mm NATO, M852 Match and M118LR ammunition are issued, both of which use Sierra MatchKing bullets; in 5.56×45mm NATO, those U.S. Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 and U.S. Marine
United States Marine Corps
The United States Marine Corps is a branch of the United States Armed Forces responsible for providing power projection from the sea, using the mobility of the United States Navy to deliver combined-arms task forces rapidly. It is one of seven uniformed services of the United States...

A sniper is a marksman who shoots targets from concealed positions or distances exceeding the capabilities of regular personnel. Snipers typically have specialized training and distinct high-precision rifles....

s who use accurized M16-type rifles are issued the Mk 262 Mod 0 cartridge developed jointly by Black Hills Ammunition
Black Hills Ammunition
Black Hills Ammunition is an American ammunition and reloading supplies manufacturing company based in Rapid City, South Dakota. Black Hills is popular among Cowboy Action Shooters because they produce quality ammunition in a number of obsolete calibers, such as .44 Russian, .38 Long Colt, .44-40...

 and Crane Naval Surface Warfare Center
Naval Surface Warfare Center Crane Division
Naval Surface Warfare Center Crane Division is the principal tenant command located at Naval Support Activity Crane. NSA Crane is a United States Navy installation located approximately southwest of Bloomington, Indiana and predominantly located in Martin County, but small parts also extend into...

, using a bullet manufactured by Sierra Bullets that was cannelured according to military specifications for this project.

In 1990, the U.S. Army Adjutant General's Office issued a legal opinion holding that the Sierra MatchKing bullet, despite being a open-tip design, is not designed specifically to cause greater damage or suffering in a human target, and in fact normally does not create a wound readily distinguishable from wounds caused by conventional full metal jacket bullets, and is therefore in their opinion legal under the Hague Convention
Hague Conventions (1899 and 1907)
The Hague Conventions were two international treaties negotiated at international peace conferences at The Hague in the Netherlands: The First Hague Conference in 1899 and the Second Hague Conference in 1907...

 for use in war.

For ultra long range precision target shooting with high-powered rifles and military sniping radically designed very-low-drag
Very-low-drag bullet
Very-low-drag bullets are primarily a small arms ballistics development of the 1980s–1990s, driven by shooters' desire for bullets that will give a higher degree of accuracy and kinetic efficiency, especially at extended ranges. To achieve this the projectile must minimize air resistance in flight...

 (VLD) bullets are available that are generally produced out of rods of mono-metal alloys on CNC
Numerical control
Numerical control refers to the automation of machine tools that are operated by abstractly programmed commands encoded on a storage medium, as opposed to controlled manually via handwheels or levers, or mechanically automated via cams alone...

A lathe is a machine tool which rotates the workpiece on its axis to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the workpiece to create an object which has symmetry about an axis of rotation.Lathes are used in woodturning,...

s. The driving force behind these projectiles is the wish to enhance the practical maximum effective range beyond normal standards. To achieve this the bullets have to be very long and normal cartridge overall lengths often have to be exceeded. Common rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...

 twist rates also often have to be tightened to stabilize very long projectiles. Such commercially nonexistent cartridges are termed "wildcats"
Wildcat cartridge
A wildcat cartridge, or wildcat, is a custom cartridge for which ammunition and firearms are not mass produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge.Developing and using wildcat cartridges does not...

. The use of a wildcat based (ultra) long-range cartridge demands the use of a custom or customized rifle with an appropriately cut chamber and a fast-twist bore. More information about these very specialized (and expensive) projectiles can be found in the very-low-drag bullet
Very-low-drag bullet
Very-low-drag bullets are primarily a small arms ballistics development of the 1980s–1990s, driven by shooters' desire for bullets that will give a higher degree of accuracy and kinetic efficiency, especially at extended ranges. To achieve this the projectile must minimize air resistance in flight...


Maximum penetration

For use against armored targets, or large, tough game animals, penetration is the most important consideration. Focusing the largest amount of momentum on the smallest possible area of the target provides the greatest penetration. Bullets for maximum penetration are designed to resist deformation upon impact, and usually are made of lead that is covered in a copper, brass, or mild steel jacket (some are even solid copper or bronze alloy). The jacket completely covers the front of the bullet, although often the rear is left with exposed lead (this is a manufacturing consideration: the jacket is formed first, and the lead is swage
Swaging is a forging process in which the dimensions of an item are altered using a die or dies, into which the item is forced. Swaging is usually a cold working process; however, it is sometimes done as a hot working process....

d in from the rear). For penetrating substances significantly harder than jacketed lead, the lead core is supplemented with or replaced with a harder material, such as hardened steel. Military armor piercing
Armor-piercing shot and shell
An armor-piercing shell is a type of ammunition designed to penetrate armor. From the 1860s to 1950s, a major application of armor-piercing projectiles was to defeat the thick armor carried on many warships. From the 1920s onwards, armor-piercing weapons were required for anti-tank missions...

 small arms ammunition is made from a copper jacketed steel core; the steel resists deformation better than the usual soft lead core leading to greater penetration. The current NATO 5.56 mm SS109 (M855) bullet uses a steel tipped lead core to improve penetration, the steel tip providing resistance to deformation for armor piercing, and the heavier lead core (25% heavier than the previous bullet, the M193) providing increased sectional density
Internal ballistics
Internal ballistics, a subfield of ballistics, is the study of a projectile's behavior from the time its propellant's igniter is initiated until it exits the gun barrel...

 for better penetration in soft targets. For larger, higher velocity calibers, such as tank guns, hardness is of secondary importance to density, and are normally sub-caliber projectiles made from tungsten carbide
Tungsten carbide
Tungsten carbide is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery,...

, tungsten hard alloy or depleted uranium
Depleted uranium
Depleted uranium is uranium with a lower content of the fissile isotope U-235 than natural uranium . Uses of DU take advantage of its very high density of 19.1 g/cm3...

  fired in a light aluminum or magnesium alloy (or carbon fibre in some cases) sabot
A sabot is a device used in a firearm or cannon to fire a projectile, such as a bullet, that is smaller than the bore diameter, or which must be held in a precise position. The term is also applied to a battery stub case, a device used similarly to make a small electrical battery usable in a...

. Many modern tank guns are smoothbore, not rifled because practical rifling twists can only stabilize projectiles, such as an armour-piercing fin-stabilized discarding sabot
Kinetic energy penetrator
A kinetic energy penetrator is a type of ammunition which, like a bullet, does not contain explosives and uses kinetic energy to penetrate the target....

 (APFSDS), with a length to diameter ratio of up to about 5:1, the spin imposed by rifling interferes with shaped charge rounds, and also because the rifling adds friction and reduces the velocity it is possible to achieve. To get the maximum force on the smallest area, anti-tank
Anti-tank warfare
Anti-tank warfare was created by the need to seek technology and tactics to destroy tanks and their supporting infantry during the First World War...

 rounds have aspect ratios of 10:1 or more. Since these cannot be stabilized by rifling, they are built instead like large darts, with fins providing the stabilizing force, negating the need for rifling. These subcaliber rounds are held in place in the bore by sabot
A sabot is a device used in a firearm or cannon to fire a projectile, such as a bullet, that is smaller than the bore diameter, or which must be held in a precise position. The term is also applied to a battery stub case, a device used similarly to make a small electrical battery usable in a...

s. The sabot is a light material that transfers the pressure of the charge to the penetrator, then is discarded when the round leaves the barrel.

Controlled penetration

The final category of bullets are those intended to maximize damage to living targets. These are used primarily for hunting and civilian antipersonnel
Anti-personnel weapon
An anti-personnel weapon is one primarily used to incapacitate people, as opposed to attacking structures or vehicles.The development of defensive fortification and combat vehicles gave rise to weapons designed specifically to attack them, and thus a need to distinguish between those systems and...

 use; they are not generally used by the military, since the use of expanding bullets in international conflicts is prohibited by the Hague Convention
Hague Conventions (1899 and 1907)
The Hague Conventions were two international treaties negotiated at international peace conferences at The Hague in the Netherlands: The First Hague Conference in 1899 and the Second Hague Conference in 1907...

. These bullets are designed to increase their surface area upon impact, thus creating greater drag and limiting the travel through the target. A desirable side effect is that the expanded bullet makes a larger hole, increasing tissue disruption and speeding incapacitation. In some applications, preventing exit from the rear of the target is also desirable. A bullet which penetrates through-and-through tends to cause more profuse bleeding, allowing a game animal to be bloodtrailed more easily. On the other hand, a perforating bullet can then continue on (likely not coaxial to the original trajectory due to target deflection) and might cause unintended damage or injury. Frangible bullets, made of tiny fragments held together by a weak binding, are often sold as an "ultimate" expanding bullet, as they will increase their effective diameter by an order of magnitude. When they work, they work extremely well, causing massive trauma to the target. On the other hand, when they fail, it is due to underpenetration, and the damage to the target is superficial and leads to very slow incapacitation.
Flat point

The simplest maximum disruption bullet is one with a wide, flat tip. This increases the effective surface area, as rounded bullets can allow tissues to "flow" around the edges. It also increases drag during flight, which decreases the depth to which the bullet penetrates. Flat point bullets, with fronts of up to 90% of the overall bullet diameter, are usually designed for use against large or dangerous game. They are often made of unusually hard alloys, are longer and heavier than normal for their caliber, and even include exotic materials such as tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...

 to increase their sectional density. These bullets are designed to penetrate deeply through muscle and bone, while causing a wound channel of nearly the full diameter of the bullet. These bullets are designed to penetrate deeply enough to reach vital organs from any shooting angle and at a far enough range. One of the common hunting applications of the flat point bullet is large game such as bear hunted with a handgun in a .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...

 or larger caliber. The disadvantage of flat point bullets is the reduction in aerodynamic performance; the flat point induces much drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

, leading to significantly reduced velocities at long range.

More effective on lighter targets are the expanding bullets, the hollow point bullet
Hollow point bullet
A hollow point is an expanding bullet that has a pit or hollowed out shape in its tip, generally intended to cause the bullet to thin upon entering a target in order to decrease penetration and disrupt more tissue as it travels through the target. It is also used for controlled penetration, where...

 and the soft point bullet
Soft point bullet
A soft-point bullet , also known as a soft-nosed bullet, is a lead expanding bullet with a copper or brass jacket that is left open at the tip, exposing some of the lead inside and is thus an example of a semi-jacketed round...

. These are designed to use the hydraulic pressure of muscle tissue to expand the bullet. The hollow point splits into eight or nine different pieces causing it to expand the damaged area. The soft point crushes upon impact then expands as the bullet starts to leave the target. This process is called mushrooming, as the ideal result is a shape that resembles a mushroom
A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence the word "mushroom" is most often applied to those fungi that...

—a cylindrical base, topped with a wide surface where the tip of the bullet has peeled back to expose more area. A copper-plated hollowpoint loaded in a .44 Magnum, for example, with an original weight
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

 of 240 grains (15.55 g) and a diameter of 0.43 inch (11 mm) might mushroom on impact to form a rough circle with a diameter of 0.70 inch (18 mm) and a final weight of 239 grains (15.48 g). This is excellent performance; almost the entire weight is retained, and the frontal surface area increased 63%. Penetration of the hollowpoint would be less than half that of a similar nonexpanding bullet, and the resulting wound or permanent cavity
Permanent cavity
Permanent cavity refers to the hole left by the passage of a projectile. It is measured as the volume of tissue or ballistics gel that has been displaced by the passage of a bullet.- See also :* Terminal ballistics* Forensic ballistics* Stopping power...

 would be much wider.

This class of projectile is designed to break apart on impact, causing an effect similar to that of a frangible projectile, whilst being of a construction more akin to that of an expanding bullet. Fragmenting bullets are usually constructed like the hollowpoint projectiles described above, but with deeper and larger cavities. They may also have thinner copper jackets in order to reduce their overall integrity. For the purposes of aerodynamic efficiency the tip of the hollowpoint will often be tipped with a pointed polymer 'nose'. These bullets are typically fired at high velocities to maximize their fragmentation upon impact. In contrast to a hollowpoint which attempts to stay in one large piece retaining as much weight as possible whilst presenting the most surface area to the target, a fragmenting bullet is intended to break up into many small pieces almost instantly. This means that all the kinetic energy from the bullet is transferred into the target in a very short space of time. The most common application of this bullet is the shooting of small vermin, such as prairie dogs. The effect of these bullets is quite dramatic, often resulting in the animal being blown apart upon impact. However on larger game fragmenting ammunition provides inadequate penetration of vital organs to ensure a clean kill, instead a "splash wound" may result. This also limits practical use of these rounds to supersonic (rifle) rounds, which have a high enough kinetic energy to ensure a lethal hit. The two main advantages of this ammunition are that it is very humane, a hit almost anywhere on most small vermin will ensure an instant kill, and that instead of dangerously and uncontrollably richocheting off surfaces, the bullet harmlessly breaks apart. Fragmenting bullets should not be confused with frangible bullets (See below).

The last category of expanding bullets are the frangible bullets. These bullets are designed to break up on impact, which results in a huge increase in surface area. The most common of these bullets are made of small diameter lead pellets, placed in a thin copper shell and held in place by an epoxy or similar binding agent. Upon impact, the epoxy shatters and the copper shell opens up, much like a hollowpoint. The individual lead balls then spread out in a wide pattern, and due to their low mass to surface area ratio, stop very quickly. Similar bullets are made out of sintered
Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature...

 metals, which turn to powder upon impact. These bullets are usually restricted to pistol cartridges, as the nonhomogenous cores tend to cause inaccuracies that, while acceptable at short pistol ranges, are not acceptable for the typical range at which rifles are used. One interesting use of the sintered metal rounds is in shotguns in hostage rescue situations; the sintered metal round is used at near-contact range to shoot the lock mechanism out of doors. The resulting metal powder will immediately disperse after knocking out the door lock, and cause little or no damage to occupants of the room. Frangible rounds are also used by armed security agents on aircraft. The concern is not depressurization (a bullet hole will not depressurise an airliner) but over penetration and damage to vital electrical or hydraulic lines, or injury to an innocent bystander by a bullet that travels through a target's body completely instead of stopping in the body.

Also used are bullets similar to hollowpoint bullets or soft point bullets whose cores and/or jackets are deliberately weakened to cause deformation or fragmentation upon impact. The Warsaw Pact
Warsaw Pact
The Warsaw Treaty Organization of Friendship, Cooperation, and Mutual Assistance , or more commonly referred to as the Warsaw Pact, was a mutual defense treaty subscribed to by eight communist states in Eastern Europe...

 5.45 x 39 mm M74 assault rifle round exemplifies a trend that is becoming common in the era of high velocity, small caliber military rounds. The 5.45 x 39 mm uses a steel jacketed bullet with a 2 part core, the rear being steel and the front being lead. Upon impact, the lead deforms, bending the bullet into a slight "L" shape. This causes the bullet to tumble in the tissue, thus increasing its effective frontal surface area by traveling sideways more often than not. This does not violate the Hague Convention, as it specifically mentions bullets that expand or flatten in the body. The NATO SS109 also tends to bend at the steel/lead junction, but with its weaker jacket, it fragments into many dozens of pieces. NATO 7.62 mm ball manufactured by some countries, such as Germany and Sweden, are also known to fragment due to jacket construction.

Other bullets in use by militaries are quite back heavy, due to a long, sharp point created in an attempt to get the maximum ballistic coefficient (see external ballistics
External ballistics
External ballistics is the part of the science of ballistics that deals with the behaviour of a non-powered projectile in flight. External ballistics is frequently associated with firearms, and deals with the behaviour of the bullet after it exits the barrel and before it hits the target.-Forces...

). These bullets will flip over after impact, then settle into a stable, back first orientation before stopping. The Swiss military actually redesigned their 5.56 mm assault rifle bullet to prevent this, to more fully comply with the spirit of the Hague Convention
Hague Conventions (1899 and 1907)
The Hague Conventions were two international treaties negotiated at international peace conferences at The Hague in the Netherlands: The First Hague Conference in 1899 and the Second Hague Conference in 1907...

, though according to some sources the present GP90 5.56x45mm Swiss assault rifle ammunition was actually designed as an armor-piercing bullet, because in the 1980s it was perceived that the Soviets and their Warsaw Pact allies were going to issue soft body armor to infantry units on a wide basis, but after the end of the Cold War, the Bofors corporation, having spent a great deal of money on developing the new bullet, changed the sales pitch in order to sell it to the Swiss government.

It might seem that if the whole purpose of a maximum disruption round is to expand to a larger diameter, it would make more sense to start out with the desired diameter rather than relying on the somewhat inconsistent results of expansion upon impact. While there is merit to this (there is a strong following of the .45 ACP
.45 ACP
The .45 ACP , also known as the .45 Auto by C.I.P., is a cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the United States Army in 1911.-Design and history:The U.S...

, as compared to the 0.355 in diameter 9 x 19 mm, for just this reason) there are also significant downsides. A larger diameter bullet is going to have significantly more drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

 than a smaller diameter bullet of the same mass, which means long range performance will be significantly degraded. A larger diameter bullet also means more space is required to store the ammunition, which means either bulkier guns or smaller magazine capacities. The common trade-off when comparing .45 ACP and 9 x 19 mm pistols is a 7 to 12 round capacity in the .45 ACP vs. a 13 to 18 round capacity in the 9x19 mm. Although several .45-caliber pistols are available with high-capacity magazines (Para Ordnance being one of the first in the late 1980s) many people find the wide grip required uncomfortable and difficult to use. Especially where the military requirement of a nonexpanding round is concerned, there is fierce debate over whether it is better to have fewer, larger bullets for enhanced terminal effects, or more, smaller bullets for increased number of potential target hits.

Selecting for terminal performance

The standard medium for testing bullets for performance on tissue is ballistic gelatin
Ballistic gelatin
Ballistic Gelatin is a testing medium scientifically correlated to swine muscle tissue , in which the effects of bullet wounds can be simulated. It was developed and improved by Martin Fackler and others in the field of wound ballistics. Ballistic gelatin is a solution of gelatin powder in water...

. Tests have shown that properly prepared and calibrated 10% (by mass) gelatin at 4 degrees Celsius correlates very closely to observed performance in the muscle tissue of living, anesthetised swine. Performance is generally graded with two factors, the maximum depth of penetration and the size of the cavity formed in the gelatin by the bullet impact. The size of the cavity represents the distance which tissue is thrown radially outward due to "splash." The penetration represents how far into the tissue the bullet will ultimately penetrate.

Unfortunately, gelatin is a poor medium for evaluating actual effectiveness. The observed "tissue splash," usually referred to as "temporary cavitation," is not an indication of terminal performance in an animal, as gelatin has a much lower elastic limit than most living tissues; a force which tears a gelatin block in half may result in nothing more than slight bruising if applied to living flesh.

Penetration figures may not be accurate. Many testers do not calibrate their gelatin. The standard calibration is 85 mm of penetration when shot by a standard .177 caliber steel bb traveling at 180 m/s (590 ft/s). Uncalibrated gelatin may show a variance of up to + or - 50% from calibrated gelatin. Further, animals' skin resists penetration much more than the muscle tissue which gelatin simulates. Human skin tissue on the torso resists penetration as much as 50 mm (2 in) of muscle, and horses' skin is the equivalent of approximately 200 mm (7.9 in).

For a quick incapacitation, a hit to a vital, blood-bearing organ or the central nervous system is needed, so a bullet that will penetrate to the depth required for such a hit should be chosen. When hunting groundhogs, for example, a bullet that expands quickly to form a large cavity with minimum penetration would be the best choice. When hunting
Hunting is the practice of pursuing any living thing, usually wildlife, for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...

 deer, a bullet which penetrates deeper is required; this can be accomplished by either limiting expansion (2 times the original width is often regarded as ideal), or by using a more powerful cartridge. For hunting bear, yet more penetration is required. The pattern is, of course, that the larger the animal, the deeper its vital organs will be located, and therefore a firearm, cartridge, and bullet type should be chosen that will be able to reach the vital organs and kill humanely.

For dangerous game especially, deep penetration depth is critical; the reason for this is that the shooter cannot always choose their shots. If a hunter finds himself staring at a deer's hindquarters, it is very unlikely that he or she will choose to fire at that deer anyway, in the hopes that their bullet will be able to reach a vital organ through several layers of muscle and gut. The better choice in that scenario would be to wait until the deer decides to turn around. A lion, however, may decide to charge at a person other than the shooter, presenting a much less than optimal shooting angle.

To hit the vital organs on a large game animal requires penetrating the thick fat and muscle tissue surrounding the chest cavity, and quite often bone as well. A hard, nondeforming bullet is often chosen, though many modern rifle calibers are quite capable of killing 1,000 lb (450 kg) elk and similar-sized animals with a deforming bullet; even the venerable .30-06 is up to the task, with a powerful enough load. Elephant hunters normally attempt to shoot for the brain, which is much smaller than the size of the elephant's head, and so must be targeted quite precisely, and require a firearm and bullet capable of punching through a foot (300 mm) or more of tough, albeit hollow, bone and reaching the brain.

Non-military defensive purposes

The rules of engagement for non-military use of firearms usually require that a life, or in some jurisdictions, property, must be in immediate danger, for shots to be fired. Under such circumstances, the goal is to incapacitate the target as quickly as possible, to prevent the harm from being done. In most cases, the shots are fired from a handgun, which is, compared to a rifle, very much underpowered. Humans are in roughly the same class as deer sized game, and in most places, the minimum cartridge power required to hunt deer is more than twice that of the average police sidearm . Handguns are also very inaccurate in the hands of inexperienced shooters, and the average defensive shooter is under a great deal of stress, which further degrades accuracy. These factors combine to require extremely effective terminal ballistics to provide swift incapacitation of the target under far less than ideal circumstances.

Humans walk upright and present relatively unprotected vital organ targets from some angles, and have substantially thinner skin, so the bare minimum penetration is lower than for deer. Cross-torso shots and shots which must first penetrate an arm are relatively common in defensive shooting scenarios, however.

Bullets for use on humans are usually designed to comply with the FBI's penetration requirement of 12 to 18 inches (30 to 46 cm), which is based on the IWBA's requirement of 12.5 to 14 inches (32 to 36 cm). This is to ensure that the bullet can reach a vital blood-bearing organ or central nervous system structure from most angles. Frangible rounds, while they are sold for defensive purposes, are not well suited for the role, as they generally penetrate less than 10 inches (25 cm), and are therefore prone to failure when they must pass through nonvital tissues, such as a hand or arm.

Hollowpoint bullets normally expand most when at their highest velocity; that is, when entering the target. As they expand, they slow. Hollowpoint bullets may not expand when they strike sheet metal, glass, or bulky clothing before the target. These preliminary obstacles can either fill the hollowpoint cavity or deform the lips of the cavity. Either of these effects can prevent the high internal hydraulic pressure necessary to make the hollowpoint round expand.

For in-depth information on the mechanisms (and misconceptions) by which bullets incapacitate living targets, see the article on stopping power
Stopping power
Stopping power is a colloquial term used to describe the ability of a firearm or other weapon to cause a penetrating ballistic injury to a target, human or animal, sufficient to incapacitate the target where it stands....


Large caliber

The purpose of firing a large calibre projectile is not always the same. For example, one might need to create disorganisation within enemy troops, create casualties within enemy troops, eliminate the functioning of an enemy tank, or destroy an enemy bunker. Different purposes of course require different projectile designs.

Many large calibre projectiles are filled with a high explosive which, when detonated, shatters the shell casing, producing thousands of high velocity fragments and an accompanying sharply rising blast overpressure. Others are more rarely used to release chemical or biological agents either on impact or when over the target area; designing an appropriate fuse
Fuse (explosives)
In an explosive, pyrotechnic device or military munition, a fuse is the part of the device that initiates function. In common usage, the word fuse is used indiscriminately...

 is a difficult task which lies outside the realm of terminal ballistics.

Other large calibre projectiles use bomblets (sub-munitions), which are released by the carrier projectile at a required height or time above their target. For US artillery ammunition these projectiles are called Dual-Purpose Improved Conventional Munition
Dual-Purpose Improved Conventional Munition
A Dual-Purpose Improved Conventional Munitions is an artillery or surface-to-surface missile warhead designed to burst into sub-munitions at an optimum altitude and distance from the desired target for dense area coverage. The sub-munitions are designed for both antiarmor and antipersonnel attack...

 (DPICM), a 155 mm M864 DPICM projectile for example contains a total of 72 shaped charge fragmentation bomblets. The use of multiple bomblets over a single HE projectile allows for a denser and less wasteful fragmentation field to be produced. If a bomblet strikes an armoured vehicle there is also a chance that the shaped charge will (if used) penetrate and disable the vehicle. A negative factor in their use is that any bomblets that fail to function go on to litter the battle field in a highly sensitive and lethal state, causing casualties long after the cessation of conflict. International conventions tend to forbid or restrict the use of this type of projectile.

Some anti-armour projectiles use what is known as a shaped charge
Shaped charge
A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, to initiate nuclear weapons, to penetrate armor, and in the oil and gas industry...

 to defeat their target. Shaped charges have been used ever since it was discovered that a block of high explosives with letters engraved in it created perfect impressions of those letters when detonated against a piece of metal. A shaped charge is an explosive charge with a hollow lined cavity at one end and a detonator at the other. They operate by the detonating high explosive collapsing the (often copper) liner into itself. Some of the collapsing liner goes on to form a constantly stretching jet of material travelling at hypersonic speed. When detonated at the correct standoff to the armour, the jet violently forces its way through the target's armour. Contrary to popular belief, the jet of a copper lined shaped charge is not molten, although it is heated to about 500 °C. This misconception is due to the metal's fluid-like behaviour, which is caused by the massive pressures produced during the explosives detonation causing the metal to flow plastically. When used in the anti-tank role, a projectile that uses a shaped charge warhead is known by the acronym HEAT
High explosive anti-tank
High explosive anti-tank warheads are made of an explosive shaped charge that uses the Munroe effect to create a very high-velocity partial stream of metal in a state of superplasticity that can punch through solid armor....

 (high explosive anti-tank).

Shaped charges can be defended against by the use of explosive reactive armour
Reactive armour
Reactive armour is a type of vehicle armour that reacts in some way to the impact of a weapon to reduce the damage done to the vehicle being protected. It is most effective in protecting against shaped charges and specially hardened long rod penetrators...

 (ERA), or complex composite armour
Composite armour
Composite armour is a type of vehicle armour consisting of layers of different material such as metals, plastics, ceramics or air. Most composite armour are lighter than their all-metal equivalent, but instead occupy a larger volume for the same resistance to penetration...

 arrays. ERA uses a high explosive sandwiched between two, relatively thin, (normally) metallic plates. The explosive is detonated when struck by the shaped charge’s jet, the detonating explosive sandwich forces the two plates apart, lowering the jets’ penetration by interfering with, and disrupting it. A disadvantage of using ERA is that each plate can protect against a single strike, and the resulting explosion can be extremely dangerous to nearby personnel and lightly armoured structures.

Tank fired HEAT projectiles are slowly being replaced for the attack of heavy armour by so-called "kinetic energy" penetrators
Kinetic energy penetrator
A kinetic energy penetrator is a type of ammunition which, like a bullet, does not contain explosives and uses kinetic energy to penetrate the target....

. Ironically, it is the most primitive (in-shape) projectiles that are hardest to defend against. A KE penetrator requires an enormous thickness of steel, or a complex armour array to protect against. They also produce a much larger diameter hole in comparison to a shaped charge and hence produce a far more extensive behind armour effect. KE penetrators are most effective when constructed of a dense tough material which is formed into a long, narrow, arrow/dart like projectile. Tungsten and depleted uranium alloys are often used as the penetrator material. The length of the penetrator is limited by the ability of the penetrator to withstand launch forces whilst in the bore and shear forces along its length at impact.


The study of projectile impacts with velocities greater than several kilometres per second is an area of active research. Such impacts are not yet used in military situations, but can arise from meteor
METEOR is a metric for the evaluation of machine translation output. The metric is based on the harmonic mean of unigram precision and recall, with recall weighted higher than precision...

ite impact. The impact of extremely small, extremely fast particles is of interest in designing spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

 to withstand erosion due to micrometeoroid
A micrometeoroid is a tiny meteoroid; a small particle of rock in space, usually weighing less than a gram. A micrometeor or micrometeorite is such a particle that enters the Earth's atmosphere or falls to Earth.-Scientific interest:...

s and small orbital debris.
Ceramic fiber
Ceramic engineering
Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high purity chemical solutions...

 woven shields offer better protection to hypervelocity (~7 km/s) particles than aluminum shields of equal weight.

One design for protection from small space debris
Space debris
Space debris, also known as orbital debris, space junk, and space waste, is the collection of objects in orbit around Earth that were created by humans but no longer serve any useful purpose. These objects consist of everything from spent rocket stages and defunct satellites to erosion, explosion...

 and micrometeroids was the multi-layer shell of NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

's TransHab
TransHab was a concept pursued by NASA to develop the technology for expandable habitats inflated by air in space. Specifically, TransHab was intended as a replacement for the already existing rigid International Space Station crew Habitation Module. When deflated, inflatable modules provide an...

 space habitation module. This technology was subsequently licensed by private
Private spaceflight
Private spaceflight is flight above Earth altitude conducted by and paid for by an entity other than a government. In the early decades of the Space Age, the government space agencies of the Soviet Union and United States pioneered space technology augmented by collaboration with affiliated design...

 company Bigelow Aerospace
Bigelow Aerospace
Bigelow Aerospace is a North Las Vegas, Nevada space technology startup company that is pioneering work on expandable space station modules. Bigelow Aerospace was founded by Robert Bigelow in 1998...

 which is pursuing a similar scheme for a private space station
Space station
A space station is a spacecraft capable of supporting a crew which is designed to remain in space for an extended period of time, and to which other spacecraft can dock. A space station is distinguished from other spacecraft used for human spaceflight by its lack of major propulsion or landing...

 design. Two Bigelow inflatable-technology space craft, Genesis I and Genesis II
Genesis II
Genesis II is a 1973 American TV film created and produced by Gene Roddenberry and directed by John Llewellyn Moxey.It opens with the line, "My name is Dylan Hunt...

, built with proprietary extensions of the NASA technology, were launched in 2006. , both spacecraft were still operating nominally after more than 10,000 orbits and traveling over 270 million miles, demonstrating significant real-world validation testing
Verification and Validation
In software project management, software testing, and software engineering, verification and validation is the process of checking that a software system meets specifications and that it fulfills its intended purpose...

 of a fabric-based ballistic shield
Ballistic shield
A ballistic shield or tactical shield is a hand-held shield that is capable of defending the user from handguns, shotguns and submachine guns. Less common are heavier and thicker rifle-protection shields that are mounted on wheels for ease of mobility...


Accelerating projectiles up to such speeds on earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 is currently difficult; light gas gun
Light gas gun
The light-gas gun is an apparatus for physics experiments, a highly specialized gun designed to generate very high velocities. It is usually used to study high speed impact phenomena , such as the formation of impact craters by meteorites or the erosion of materials by micrometeoroids...

s are currently the most common techniques for producing such speeds, although linear motor
Linear motor
A linear motor is an electric motor that has had its stator and rotor "unrolled" so that instead of producing a torque it produces a linear force along its length...

s, railgun
A railgun is an entirely electrical gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the homopolar motor. Railguns use two sliding or rolling contacts that permit a large electric current to pass through the projectile. This current interacts...

s, coilguns and ram accelerator
Ram accelerator
A ram accelerator has the same function as a gun; i.e., it is a device for accelerating projectiles; however, it is entirely different in that jet-engine-like propulsion cycles utilizing ramjet and/or scramjet combustion processes are used to accelerate a projectile to extremely high speeds...

s are also possibilities undergoing active research. In 2005, Bigelow Aerospace utilized an earthbound test apparatus firing 1.7-cm-diameter aluminum projectiles into its inflatable spacecraft multilayer shield technology at 7 km per second.

See also Kinetic energy penetrator
Kinetic energy penetrator
A kinetic energy penetrator is a type of ammunition which, like a bullet, does not contain explosives and uses kinetic energy to penetrate the target....


See also

  • Forensic ballistics
  • Gunshot injury
  • Hydrostatic shock
    Hydrostatic shock
    Hydrostatic shock or hydraulic shock describes the observation that a penetrating projectile can produce remote wounding and incapacitating effects in living targets through a hydraulic effect in their liquid-filled tissues, in addition to local effects in tissue caused by direct impact...

  • Stopping power
    Stopping power
    Stopping power is a colloquial term used to describe the ability of a firearm or other weapon to cause a penetrating ballistic injury to a target, human or animal, sufficient to incapacitate the target where it stands....

  • Taylor KO factor
    Taylor KO Factor
    Taylor KO Factor is a commonly used mathematical approach for evaluating the stopping power of hunting cartridges. The term "KO" is an acronym for "Knock Out." The Taylor KO Factor is a figure of merit that allows hunters to compare bullets with respect to stopping power...

  • Vaporific effect
    Vaporific Effect
    Vaporific effect is a flash fire resulting from the impact of high velocity projectiles with metallic objects. Impacts produce particulate matter originating from either the projectile, the target, or both. Particles heated from the force of impact can burn in the presence of air...

External links

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