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A bullet is a kinetic projectile, a component of
firearm A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and operated by an individual. The term is legally defined further in different countries (see legal definitions). The first firearms originate ...
ammunition Ammunition, also known as ammo, is the material fired, scattered, dropped, or detonated from any weapon or weapon system. The term includes both expendable weapons (e.g., bombs, missiles, grenades, land mines), and the component parts of oth ...
that is shot from a
gun barrel A gun barrel is a crucial part of gun-type weapons such as small arms, small firearms, artillery pieces, and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high ...
. They are made of a variety of materials, such as
copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
,
lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
,
steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...
,
polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...
,
rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of polyisoprene ...
and even wax; and are made in various shapes and constructions (depending on the intended applications), including specialized functions such as
hunting Hunting is the Human activity, human practice of seeking, pursuing, capturing, and killing wildlife or feral animals. The most common reasons for humans to hunt are to obtain the animal's body for meat and useful animal products (fur/hide (sk ...
, target shooting, training, and combat. Bullets are often tapered, making them more
aerodynamic Aerodynamics () is the study of the motion of atmosphere of Earth, air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dynamics and its subfield of gas dynamics, and is an ...
. Bullet size is expressed by weight and diameter (referred to as "
caliber In guns, particularly firearms, but not #As a measurement of length, artillery, where a different definition may apply, caliber (or calibre; sometimes abbreviated as "cal") is the specified nominal internal diameter of the gun barrel Gauge ( ...
") in both imperial and metric measurement systems. Bullets do not normally contain
explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ex ...
s but strike or damage the intended target by transferring
kinetic energy In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...
upon impact and penetration.


Description

The term ''bullet'' is from Early French, originating as the
diminutive A diminutive is a word obtained by modifying a root word to convey a slighter degree of its root meaning, either to convey the smallness of the object or quality named, or to convey a sense of intimacy or endearment, and sometimes to belittle s ...
of the word ''boulle'' (''boullet''), which means "small ball". Bullets are available singly (as in
muzzle-loading A muzzleloader is any firearm in which the user loads the projectile and the propellant charge into the muzzle end of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the modern designs of breech-loading fire ...
and cap and ball firearms) but are more often packaged with propellant as a cartridge ("round" of ammunition) consisting of the ''bullet'' (i.e., the projectile), the ''case'' (which holds everything together), the ''
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicle ...
'' (which provides the majority of the energy to launch the projectile), and the '' primer'' (which ignites the propellant). Cartridges, in turn, may be held in a ''magazine'', a clip, or a ''belt'' (for rapid-fire
automatic firearm An automatic firearm or fully automatic firearm (to avoid confusion with semi-automatic firearms) is a self-loading firearm that continuously Chamber (firearms), chambers and fires Cartridge (firearms), rounds when the trigger (firearms), trigger ...
s). Although the word ''bullet'' is often used in colloquial language to refer to a cartridge round, a bullet is ''not'' a cartridge but rather a component of one. This use of the term ''bullet'' (when intending to describe a cartridge) often leads to confusion when a cartridge and all its components are specifically being referenced. The sound of gunfire (i.e. the "muzzle report") is often accompanied with a loud bullwhip-like crack as the
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
bullet pierces through the air, creating a
sonic boom A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to ...
. Bullet speeds at various stages of flight depend on intrinsic factors such as sectional density, aerodynamic profile and
ballistic coefficient In ballistics, the ballistic coefficient (BC, ''C'') of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to the negative acceleration: a high number indicates a low negative acceleration—the ...
, as well as extrinsic factors such as
barometric pressure Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013.2 ...
, humidity, air temperature and wind speed. Subsonic cartridges fire bullets slower than the speed of sound, so there are no sonic booms. This means that a subsonic cartridge, such as .45 ACP, can be substantially quieter than a supersonic cartridge, such as the .223 Remington, even without the use of a
suppressor A silencer, also known as a sound suppressor, suppressor, or sound moderator, is a gun barrel#Muzzle, muzzle device that suppresses the muzzle blast, blast created when a gun (firearm or airgun) is discharged, thereby reducing the sound inten ...
. Bullets shot by firearms can be used for
target practice Target practice is a key part of both military training and shooting sports. It involves exercises where people shoot weapons at specific targets. The main goal is to improve the shooter's accuracy and skill with firearms. Through repeated pra ...
or to injure or kill animals or people. Death can be by
blood loss Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, v ...
or damage to vital organs, or even
asphyxia Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects all the tissues and organs, some more rapidly than others. There are m ...
tion if blood enters the lungs. Bullets are not the only projectiles shot from firearm-like equipment: BBs are shot from
BB gun A BB gun is a type of air gun designed to shoot metallic spherical projectiles called BBs (not to be confused with similar-looking bearing balls), which are approximately the same size as BB-size lead birdshot used in shotguns ( in diameter) ...
s, airsoft pellets are shot by
airsoft gun Airsoft guns are air guns used in airsoft sports. They are a special type of low-power smoothbore guns designed to shoot Airsoft pellets, plastic pellets often colloquially (but incorrectly) referred to as "BB (ammunition), BBs", which are typ ...
s, paintballs are shot by
paintball marker A paintball marker, also known as a paintball gun, paint gun, or simply marker, is an air gun used in the shooting sport of paintball, and the main piece of paintball equipment. Paintball markers use compressed gas, such as carbon dioxide (CO2) ...
s, and small rocks can be hurtled from
slingshot A slingshot or catapult is a small hand-powered projectile weapon. The classic form consists of a Y-shaped frame, with two tubes or strips made from either a natural rubber or synthetic elastic material. These are attached to the upper two ends ...
s. There are also flare guns, potato guns (and spud guns),
taser Taser (stylized in all caps) is a line of handheld conducted energy devices (CED) sold by Axon Enterprise (formerly Taser International). The device fires two small barbed darts intended to puncture the skin and remain attached to the targe ...
s,
bean bag round A bean bag round, also known by its trademarked name flexible baton round, is a type of baton round, fired from a shotgun, and used for Non-lethal weapon, less lethal apprehension of suspects. Description The bean bag round typically consists ...
s,
grenade launcher A grenade launcher is a weapon that fires a specially designed, large caliber projectile, often with an explosive, Smoke screen, smoke, or tear gas, gas warhead. Today, the term generally refers to a class of dedicated firearms firing unitary gre ...
s, flash bangs,
tear gas Tear gas, also known as a lachrymatory agent or lachrymator (), sometimes colloquially known as "mace" after the Mace (spray), early commercial self-defense spray, is a chemical weapon that stimulates the nerves of the lacrimal gland in the ey ...
, RPGs, and
missile launchers A rocket launcher is a weapon that launches an unguided, rocket-propelled projectile. History The earliest rocket launchers documented in imperial China consisted of arrows modified by the attachment of a rocket motor to the shaft a few i ...
.


Speed

Bullets used in many cartridges are fired at muzzle velocities faster than the
speed of sound The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elasticity (solid mechanics), elastic medium. More simply, the speed of sound is how fast vibrations travel. At , the speed of sound in a ...
—about in dry air at —and thus can travel substantial distances to their targets before any nearby observers hear the sound of the shots. Rifle bullets, such as that of a Remington 223 firing lightweight varmint projectiles from a barrel, leave the muzzle at speeds of up to . A bullet from a 9 mm Luger handgun, reaches speeds of only . Similarly, an
AK-47 The AK-47, officially known as the Avtomat Kalashnikova (; also known as the Kalashnikov or just AK), is an assault rifle that is chambered for the 7.62×39mm cartridge. Developed in the Soviet Union by Russian small-arms designer Mikhail Kala ...
, has a muzzle velocity of about .


History

The first true gun evolved in China from the fire lance (a bamboo tube that fired porcelain shrapnel) with the invention of the metal hand cannon sometime around 1288, which the
Yuan dynasty The Yuan dynasty ( ; zh, c=元朝, p=Yuáncháo), officially the Great Yuan (; Mongolian language, Mongolian: , , literally 'Great Yuan State'), was a Mongol-led imperial dynasty of China and a successor state to the Mongol Empire after Div ...
used to win a decisive victory against Mongolian rebels. The artillery
cannon A cannon is a large-caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder during th ...
appeared in 1326 and the European
hand cannon The hand cannon ( or ), also known as the gonne or handgonne, is the first true firearm and the successor of the fire lance. It is the oldest type of small arms, as well as the most mechanically simple form of metal barrel firearms. Unlike match ...
in 1364. Early projectiles were made of stone. Eventually it was discovered that stone would not penetrate stone fortifications, which led to the use of denser materials as projectiles. Hand cannon projectiles developed in a similar manner. The first recorded instance of a metal ball from a hand cannon penetrating armor was in 1425. Shot retrieved from the wreck of the ''
Mary Rose The ''Mary Rose'' was a carrack in the English Tudor navy of Henry VIII of England, King Henry VIII. She was launched in 1511 and served for 34 years in several wars against France, Scotland, and Brittany. After being substantially rebuilt in ...
'' (sunk in 1545, raised in 1982) are of different sizes, and some are stone while others are cast iron. The development of the hand
culverin A culverin was initially an ancestor of the hand-held arquebus, but the term was later used to describe a type of medieval and Renaissance cannon. The word is derived from the antiquated "culuering" and the French (from " grass snake", follo ...
and
matchlock A matchlock or firelock is a historical type of firearm wherein the gunpowder is ignited by a burning piece of flammable cord or twine that is in contact with the gunpowder through a mechanism that the musketeer activates by pulling a lever or Tri ...
arquebus An arquebus ( ) is a form of long gun that appeared in Europe and the Ottoman Empire during the 15th century. An infantryman armed with an arquebus is called an arquebusier. The term ''arquebus'' was applied to many different forms of firearms ...
brought about the use of
cast Cast may refer to: Music * Cast (band), an English alternative rock band * Cast (Mexican band), a progressive Mexican rock band * The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis * ''Cast'', a 2012 album by Trespassers William ...
lead balls as projectiles. The original round
musket A musket is a muzzle-loaded long gun that appeared as a smoothbore weapon in the early 16th century, at first as a heavier variant of the arquebus, capable of penetrating plate armour. By the mid-16th century, this type of musket gradually dis ...
ball was smaller than the bore of the barrel. At first it was loaded into the barrel just resting upon the powder. Later, some sort of material was used as a
wadding Wadding is a disc of material used in guns to seal gas behind a projectile (a bullet or ball), or to separate the propellant from loosely packed shots. Wadding can be crucial to a gun's efficiency, since any gas that leaks past a projectile ...
between the ball and the powder as well as over the ball to keep it in place, it held the bullet firmly in the barrel and against the powder. (Bullets not firmly set on the powder risked exploding the barrel, with the condition known as a "short start".) The loading of muskets was therefore easy with the old smooth-bore
Brown Bess "Brown Bess" is a nickname of uncertain origin for the British Army's Muzzleloader, muzzle-loading smoothbore flintlock Land Pattern Musket and its derivatives. The musket design remained in use for over a hundred years with many incremental c ...
and similar military muskets. The original muzzle-loading
rifle A rifle is a long gun, long-barreled firearm designed for accurate shooting and higher stopping power, with a gun barrel, barrel that has a helical or spiralling pattern of grooves (rifling) cut into the bore wall. In keeping with their focus o ...
, however, was loaded with a piece of leather or cloth wrapped around the ball, to allow the ball to engage the grooves in the barrel. Loading was a bit more difficult, particularly when the bore of the barrel was fouled from previous firings. For this reason, and because rifles were not often fitted for
bayonet A bayonet (from Old French , now spelt ) is a -4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, that is, when it wa ... , now spelt ) is a knife, dagger">knife">-4; we might wonder whethe ...
s, early rifles were rarely used for military purposes, compared to muskets. There was a distinct change in the shape and function of the bullet during the first half of the 19th century, although experiments with various types of elongated projectiles had been made in Britain, America and France from the first half of the 18th century onwards. In 1816, Capt. George Reichenbach of the Bavarian army invented a rifled-wall musket using cylindro-conical ammunition. In 1826,
Henri-Gustave Delvigne Henri-Gustave Delvigne (April 10, 1800 in Hamburg – October 18, 1876 in Toulon) was a French soldier and inventor. He became a captain in the French infantry service, from which he resigned on the outbreak of the 1830 July Revolution. Delvig ...
, a French
infantry Infantry, or infantryman are a type of soldier who specialize in ground combat, typically fighting dismounted. Historically the term was used to describe foot soldiers, i.e. those who march and fight on foot. In modern usage, the term broadl ...
officer, invented a breech with abrupt shoulders on which a spherical bullet was rammed down until it caught the
rifling Rifling is the term for helical grooves machined into the internal surface of a firearms's barrel for imparting a spin to a projectile to improve its aerodynamic stability and accuracy. It is also the term (as a verb) for creating such groov ...
grooves. Delvigne's method, however, deformed the bullet and was inaccurate. In 1855, a detachment of 1st U.S. Dragoons, while on patrol, traded lead for gold bullets with Pima Indians along the California–Arizona border. Square bullets have origins that almost pre-date civilization and were used in slings. They were typically made out of copper or lead. The most notable use of square bullet designs was by James Puckle and Kyle Tunis who patented them, where they were briefly used in one version of the
Puckle gun The Puckle gun (also known as the defence gun) was a primitive Crew-served weapon, crew-served, manually operated flintlock revolver patented in 1718 by James Puckle (1667–1724), a British inventor, lawyer and writer. It was one of the earlies ...
. The early use of these in the black-powder era was soon discontinued because of the irregular and unpredictable flight patterns.


Pointed bullets

Delvigne continued to develop bullet design and by 1830 had started to develop cylindro-conical bullets. His bullet designs were improved by Francois Tamisier with the addition of "ball grooves" which are known as " cannelures", which moved the resistance of air behind the center of gravity of the bullet. Tamisier also developed progressive rifling: the rifle grooves were deeper toward the breech, becoming shallower as they progressed toward the muzzle. This causes the bullet to be progressively molded into the grooves which increases range and accuracy. Among the first pointed or "conical" bullets were those designed by Captain John Norton of the
British Army The British Army is the principal Army, land warfare force of the United Kingdom. the British Army comprises 73,847 regular full-time personnel, 4,127 Brigade of Gurkhas, Gurkhas, 25,742 Army Reserve (United Kingdom), volunteer reserve perso ...
in 1832. Norton's bullet had a hollow base made of lotus pith that on firing expanded under pressure to engage with a barrel's rifling. The British Board of Ordnance rejected it because spherical bullets had been in use for the previous 300 years. Renowned English gunsmith William Greener invented the Greener bullet in 1836. Greener fitted the hollow base of an oval bullet with a wooden plug that more reliably forced the base of the bullet to expand and catch the rifling. Tests proved that Greener's bullet was effective, but the military rejected it because, being two parts, they judged it as too complicated to produce. The carabine à tige, developed by Louis-Étienne de Thouvenin in 1844, was an improvement of Delvigne's design. The rifle barrel has a forcing plug in the breech of the barrel to mold the bullet into the rifling with the use of a special
ramrod A ramrod (or scouring stick) is a metal or wooden device used with muzzleloader, muzzleloading firearms to push the projectile up against the propellant (mainly blackpowder). The ramrod was used with weapons such as muskets and cannons and was u ...
. While successful in increasing accuracy, it was difficult to clean. The soft lead
Minié ball The Minié ball, or Minie ball, is a type of hollow-based bullet designed by Claude-Étienne Minié for muzzle-loaded, rifled muskets. Invented in 1846 shortly followed by the Minié rifle, the Minié ball came to prominence during the Crime ...
was first introduced in 1847 by Claude-Étienne Minié, a captain in the French Army. It was another improvement of the work done by Delvigne. The bullet was conical in shape with a hollow cavity in the rear, which was fitted with a small iron cap instead of a wooden plug. When fired, the iron cap forced itself into the hollow cavity at the rear of the bullet, thus expanding the sides of the bullet to grip and engage the rifling. In 1851, the British adopted the Minié ball for their 702-inch Pattern 1851 Minié rifle. In 1855, James Burton, a machinist at the U.S. Armory at Harper's Ferry, West Virginia, improved the Minié ball further by eliminating the metal cup in the bottom of the bullet. The Minié ball first saw widespread use in the
Crimean War The Crimean War was fought between the Russian Empire and an alliance of the Ottoman Empire, the Second French Empire, the United Kingdom of Great Britain and Ireland, and the Kingdom of Sardinia (1720–1861), Kingdom of Sardinia-Piedmont fro ...
(1853–1856). Roughly 90% of the battlefield casualties in the
American Civil War The American Civil War (April 12, 1861May 26, 1865; also known by Names of the American Civil War, other names) was a civil war in the United States between the Union (American Civil War), Union ("the North") and the Confederate States of A ...
(1861–1865) were caused by Minié balls fired from rifled muskets. A similar bullet called the Nessler ball was also developed for smoothbore muskets. Between 1854 and 1857, Sir
Joseph Whitworth Sir Joseph Whitworth, 1st Baronet (21 December 1803 – 22 January 1887) was an English engineer, entrepreneur, inventor and philanthropist. In 1841, he devised the British Standard Whitworth system, which created an accepted standard for screw ...
conducted a long series of rifle experiments and proved, among other points, the advantages of a smaller bore and, in particular, of an elongated bullet. The Whitworth bullet was made to fit the grooves of the rifle mechanically. The Whitworth rifle was never adopted by the government, although it was used extensively for match purposes and target practice between 1857 and 1866. In 1861, W. B. Chace approached President
Abraham Lincoln Abraham Lincoln (February 12, 1809 – April 15, 1865) was the 16th president of the United States, serving from 1861 until Assassination of Abraham Lincoln, his assassination in 1865. He led the United States through the American Civil War ...
with an improved ball design for muskets. In firing over the
Potomac River The Potomac River () is in the Mid-Atlantic (United States), Mid-Atlantic region of the United States and flows from the Potomac Highlands in West Virginia to Chesapeake Bay in Maryland. It is long,U.S. Geological Survey. National Hydrography D ...
, where the Chace ball and the round ball were alternated, Lincoln observed that the Chace design carried a third or more farther fired at the same elevation. Although Lincoln recommended testing, it never took place. Around 1862, W. E. Metford carried out an exhaustive series of experiments on bullets and rifling, and he invented the important system of light rifling with increasing spiral and a hardened bullet. The combined result was that, in December 1888, the Lee–Metford small-bore ( .303", 7.70 mm) rifle, Mark I, was adopted for the British army. The Lee–Metford was the predecessor of the
Lee–Enfield The Lee–Enfield is a bolt-action, magazine-fed repeating rifle that served as the main firearm of the military forces of the British Empire and Commonwealth during the first half of the 20th century, and was the standard service rifle of th ...
.


Modern bullets

The next important change in the history of the rifle bullet occurred in 1882, when Lieutenant Colonel Eduard Rubin, director of the Swiss Army Laboratory at Thun, invented the copper-jacketed bullet — an elongated bullet with a lead core in a copper jacket. It was also small bore (7.5 and 8 mm) and it is the precursor of the 8 mm ''Lebel bullet'' adopted for the
smokeless powder Finnish smokeless powder Smokeless powder is a type of propellant used in firearms and artillery that produces less smoke and less fouling when fired compared to black powder. Because of their similar use, both the original black powder formula ...
ammunition of the Lebel Model 1886 rifle. The surface of lead bullets fired at high velocity may melt from the hot gases behind and friction within the bore. Because copper has a higher
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...
, and greater
specific heat capacity In thermodynamics, the specific heat capacity (symbol ) of a substance is the amount of heat that must be added to one unit of mass of the substance in order to cause an increase of one unit in temperature. It is also referred to as massic heat ...
, and higher hardness, copper-jacketed bullets allow greater muzzle velocities. European advances in aerodynamics led to the pointed Spitzer (bullet), spitzer bullet. By the beginning of the 20th century, most world armies had begun the transition to spitzer bullets. These bullets flew for greater distances more accurately and transferred more
kinetic energy In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...
. Spitzer bullets combined with machine guns greatly increased lethality on the battlefield. Spitzer bullets were streamlined at the base with the External ballistics#General trends in drag or ballistic coefficient, boat tail. In the trajectory of a bullet, as air passes over a bullet at high speed, a vacuum is created at the end of the bullet, slowing the projectile. The streamlined boat tail design reduces this Parasitic drag, form drag by allowing the air to flow along the surface of the tapering end. The resulting aerodynamic advantage is currently seen as the optimum shape for rifle technology. The first combination spitzer and boat-tail bullet, named ''balle'' D by its inventor Captain Georges Desaleux, was introduced as standard military ammunition in 1901, for the French Lebel Model 1886 rifle. A Plastic-tipped bullet, ballistic tip bullet is a Hollow-point bullet, hollow-point rifle bullet that has a plastic tip on the end of the bullet. This improves external ballistics by streamlining the bullet, allowing it to cut through the air more easily, and improves terminal ballistics by allowing the bullet to act as a jacketed hollow point. As a side effect, it also feeds better in weapons that have trouble feeding rounds that are not full metal jacket rounds.


Design

Bullet designs have to solve two primary problems. In the barrel, they must first form a seal with the gun's bore. If a strong seal is not achieved, gas from the propellant charge leaks past the bullet, thus reducing efficiency and possibly accuracy. The bullet must also engage the rifling without damaging or excessively fouling the gun's bore and without distorting the bullet, which will also reduce accuracy. Bullets must have a surface that forms this seal without excessive friction. These interactions between bullet and bore are termed internal ballistics. Bullets must be produced to a high standard, as surface imperfections can affect firing accuracy. The physics affecting the bullet once it leaves the barrel is termed external ballistics. The primary factors affecting the aerodynamics of a bullet in flight are the bullet's shape and the rotation imparted by the rifling of the gun barrel. Rotational forces stabilize the bullet gyroscopically as well as aerodynamically. Any asymmetry in the bullet is largely canceled as it spins. However, a spin rate greater than the optimum value adds more trouble than good, by magnifying the smaller asymmetries or sometimes resulting in the bullet breaking apart in flight. With smooth-bore firearms, a spherical shape is optimal because no matter how the bullet is oriented, its aerodynamics are similar. These unstable bullets tumble erratically and provide only moderate accuracy; however, the aerodynamic shape changed little for centuries. Generally, bullet shapes are a compromise between aerodynamics, interior ballistic necessities, and terminal ballistics requirements. Terminal ballistics and stopping power are aspects of bullet design that affect what happens when a bullet impacts with an object. The outcome of the impact is determined by the composition and density of the target material, the Angle of incidence (aerodynamics), angle of incidence, and the velocity and physical characteristics of the bullet. Bullets are generally designed to penetrate, deform, or break apart. For a given material and bullet, the strike velocity is the primary factor that determines which outcome is achieved. Bullet shapes are many and varied. With a mold, bullets can be made at home for reloading ammunition, where local laws allow. Hand-casting, however, is only time- and cost-effective for solid lead bullets. Cast and jacketed bullets are also commercially available from numerous manufacturers for handloading and are most often more convenient than casting bullets from bulk or scrap lead. In recent years, manufacturers have introduced bullet designs that rely on computer numerical control (CNC) machining to achieve precise, repeatable geometries not possible with traditional swaging or casting. These designs often feature patented profiles with radial flutes, pressure cavities, or meplat modifications intended to manipulate fluid displacement, induce controlled expansion, or promote bullet tumbling upon impact. One notable example includes the designs patented by Lehigh Defense, which incorporate machined flutes that channel hydraulic force to create large wound cavities and ensure consistent terminal performance. These bullets are often monolithic in composition and used in hunting and self-defense contexts where expansion and barrier penetration are critical.


Propulsion

Propulsion of the ball can happen via several methods: * by using only gunpowder (as in flintlock, wheellock, or
matchlock A matchlock or firelock is a historical type of firearm wherein the gunpowder is ignited by a burning piece of flammable cord or twine that is in contact with the gunpowder through a mechanism that the musketeer activates by pulling a lever or Tri ...
weapons) * by using a percussion cap and gunpowder (as in percussion weapons) * by using a cartridge


Materials

Bullets for black powder, or muzzle-loading firearms, were classically molded from pure
lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
. This worked well for low-speed bullets, fired at velocities of less than 450 m/s (1,475 ft/s). For slightly higher-speed bullets fired in modern firearms, a harder alloy of lead and tin or typesetter's lead (used to mold Linotype (alloy), linotype) works very well. For even higher-speed bullet use, jacketed lead bullets are used. The common element in all of these, lead, is widely used because it is very dense, thereby providing a high amount of mass—and thus, kinetic energy—for a given volume. Lead is also cheap, easy to obtain, easy to work, and melts at a low temperature, which results in comparatively easy fabrication of bullets. * ''Lead'': simple Cast bullet, cast, extruded, swaging, swaged, or otherwise fabricated lead Slug (disambiguation), slugs are the simplest form of bullets. At speeds of greater than 300 Meter per second, m/s (1,000 ft/s) (common in most handguns), lead is deposited in rifled bores at an ever-increasing rate. Alloying the lead with a small percentage of tin and/or antimony serves to reduce this effect but grows less effective as velocities are increased. A cup made of harder metal, such as copper, placed at the base of the bullet and called a gas check, is often used to decrease lead deposits by protecting the rear of the bullet against melting when fired at higher pressures, but this does not solve the problem at higher velocities. A modern solution is to Powder coating, powder coat the lead projectile, encasing it in a protective skin, allowing higher velocities to be achieved without lead deposits. * ''Jacketed lead'': bullets intended for even higher-velocity applications generally have a lead core that is jacketed or plated with gilding metal, cupronickel,
copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
alloys, or
steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...
; a thin layer of harder metal protects the softer lead core when the bullet is passing through the barrel and during flight, which allows delivering the bullet intact to the target. There, the heavy lead core delivers its kinetic energy to the target. Full metal jacket or "ball" bullets (cartridges with ball bullets, which despite the name are not spherical, are called ball ammunition) are completely encased in the harder metal jacket, except for the base. Some bullet jackets do not extend to the front of the bullet, to aid expansion and increase lethality; these are called soft point (if the exposed lead tip is solid) or hollow point bullets (if a cavity or hole is present). Steel bullets are often plated with copper or other metals for corrosion resistance during long periods of storage. Synthetic jacket materials such as nylon and Polytetrafluoroethylene, Teflon have been used, with limited success, especially in rifles; however, hollow point bullets with plastic aerodynamic tips have been very successful at both improving accuracy and enhancing expansion. Newer plastic coatings for handgun bullets, such as Teflon-coated bullets, are making their way into the market. * ''Solid'' or ''Monolithic bullet, monolithic solid'': mono-metal bullets intended for deep penetration in big game animals and slender shaped very-low-drag projectiles for long range shooting are produced out of metals like oxygen-free copper and alloys like cupronickel, tellurium copper and brass (e.g., highly machinable UNS C36000 free-cutting brass). Often these projectiles are turned on precision Lathe (metal)#CNC lathe / CNC turning center, CNC lathes. In the case of solids, and the ruggedness of the game animals on which they are used, e.g., the African buffalo or elephant, expansion is almost entirely relinquished for the necessary penetration. In shotgunning, "slug" loads are often solid large single lead projectiles, sometimes with a hollow point, used for deer or wild pig hunting in jurisdictions that do not allow hunting with rifles (because a missed slug shot will travel considerably less far than a rifle bullet). **''Fluted'': in appearance, these are solid bullets with scalloped sides (missing material). The theory is that the flutes produce hydraulic jetting when passing through tissue, creating a wound channel larger than that made by conventional Expanding bullet, expanding ammunition such as hollow point bullets. **''Hard cast'': a hard lead alloy intended to reduce fouling of rifling grooves (especially of the polygonal rifling used in some popular pistols). Benefits include simpler manufacture than jacketed bullets and good performance against hard targets; limitations are an inability to Hollow-point bullet#Expansion, mushroom and subsequent over-penetration of soft targets. * ''Blank (cartridge), Blank'': wax, paper, plastic, and other materials are used to simulate live gunfire and are intended only to hold the powder in a blank cartridge and to produce noise, flame and smoke. The "bullet" may be captured in a purpose-designed device or it may be allowed to expend what little energy it has in the air. Some blank cartridges are crimped or closed at the end and do not contain any bullet; some are fully loaded cartridges (without bullets) designed to propel rifle grenades. The force of the expanding gas from blank cartridges can be lethal at short range; fatal accidents have occurred with blank cartridges (e.g., the death of actor Jon-Erik Hexum). * ''Practice'': made from lightweight materials like rubber, Wax bullet, wax, wood, plastic, or lightweight metal, practice bullets are intended for short-range target work only. Because of their weight and low velocity, they have limited range. * ''Polymer'': these are metal-polymer composites, generally lighter and having higher velocities than pure metal bullets of the same dimensions. They permit unusual designs that are difficult with conventional casting or lathing. * ''Less lethal'', or ''less than lethal'': Rubber bullets, plastic bullets, and Bean bag round, beanbags are designed to be Non-lethal weapon, non-lethal, e.g., for use in riot control. They are generally low velocity and are fired from shotguns, grenade launchers, paint ball guns, or specially designed firearms and air gun devices. * ''Incendiary ammunition, Incendiary'': these bullets are made with explosive or flammable mixtures in the tips that are designed to ignite on contact with a target. The intent is to ignite fuel or munitions in the target area, thereby adding to the destructive power of the bullet. * ''High-explosive incendiary/armor-piercing ammunition, Exploding'': similar to the incendiary bullet, this type of projectile is designed to explode upon hitting a hard surface, preferably the bone of the intended target. Not to be mistaken for cannon shells or grenades with fuse devices, these bullets have only cavities filled with a small amount of high explosive depending on the velocity and deformation upon impact to detonate. Exploding bullets have been used in various heavy machine guns and in anti-materiel rifles. * ''Tracer ammunition, Tracer'': these have hollow backs, filled with a flare material. Usually this is a mixture of magnesium, a perchlorate, and strontium salts to yield a bright red color, although other materials providing other colors have also sometimes been used. Tracer material burns out after a certain amount of time. This allows the shooter to visually trace the flight path of the projectile and thus make necessary ballistic corrections, without having to confirm projectile impacts and without even using the Sight (device), sights of the weapon. This type of round is also used by all branches of the United States Armed Forces, United States military in combat environments as a signaling device to friendly forces. Normally it is loaded at a four to one ratio with ball ammunition. * ''armor-piercing bullet, Armor-piercing'': jacketed designs where the core material is a very hard, high-density metal such as tungsten, tungsten carbide, depleted uranium, or
steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...
. A pointed tip is often used, but a flat tip on the penetrator portion is generally more effective. * ''Nontoxic shot'': steel, bismuth, tungsten, and other alloys prevent release of toxic lead into the environment. Regulations in several countries mandate the use of nontoxic projectiles especially when waterfowl hunting. It has been found that birds swallow small lead shot for their gizzards to grind food (as they would swallow pebbles of similar size), and the effects of Animal lead poisoning, lead poisoning by grinding of lead pellets against food means lead poisoning effects are magnified. Such concerns apply primarily to shotguns firing pellets (Shotgun shell, shot) and not bullets, but there is evidence suggesting that consumption of spent rifle and pistol ammunition is also hazardous to wildlife. Reduction of hazardous substances legislation has also been applied to bullets on occasion to reduce the impact of lead on the environment at shooting ranges. * ''Blended-metal bullets, Blended-metal'': bullets made using cores from powdered metals other than lead with binder or sometimes sintering, sintered. * ''Frangible bullet, Frangible'': designed to disintegrate into tiny particles upon impact to minimize their penetration for reasons of range safety, to limit environmental impact, or to limit the shoot-through danger behind the intended target. An example is the Glaser Safety Slug, usually a pistol caliber bullet made from an amalgam of lead shot and a hard (and thus frangible) plastic binder designed to penetrate a human target and release its component shot pellets without exiting the target. * ''Multiple projectile'': bullets that are made of separate slugs that fit together inside the cartridge and act as a single projectile inside the barrel as they are fired. The projectiles part in flight but are held in formation by tethers that keep the individual parts of the "bullet" from flying too far away from each other. The intention of such ammo is to increase hit chance by giving a shot-like spread to rifled slug firing guns, while maintaining a consistency in shot groupings. Multiple impact bullets may be less stable in flight than conventional solid bullets because of the added Drag (physics), drag from the tether line holding the pieces in formation, and each projectile affects the flight of all the others. This may limit the benefit provided by the spread of each bullet at longer ranges. * Expanding bullets are designed to increase in diameter upon impact with a target, maximizing the transfer of energy and creating a larger wound channel. These bullets are often made with a
lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
core and a
copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
jacket, though variations like MRX bullets have tungsten in its core. The
polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...
tip in expanding bullets is designed to enhance aerodynamics for shooting at flat long-range trajectories.


Treaties and prohibitions

Poisonous bullets were a subject to an international agreement as early as the Strasbourg Agreement (1675). The Saint Petersburg Declaration of 1868 prohibited the use of explosive projectiles weighing less than 400 grams. The Hague Conventions of 1899 and 1907, Hague Conventions prohibits certain kinds of ammunition for use in war. These include poisoned and expanding bullets. Protocol on Incendiary Weapons, Protocol III of the 1983 Convention on Certain Conventional Weapons, an annexed protocol to the Geneva Conventions, prohibits the use of incendiary ammunitions against civilians.


Types of bullets

Some types of bullets include: Please do not add any and every manufacturer's version of every bullet available, only list bullet types with their own articles * Armor-piercing shot and shell, Armor piercing (sometimes with a depleted uranium or other heavy metal core) * APFSDS, Armor-piercing fin stabilized discarding sabot round * Cast bullet, Cast * Expanding bullet, Expanding (Hollow-point bullet, hollow point, Soft-point bullet, soft point) * Frangible bullet, Frangible * Full metal jacket (ammunition), Full metal jacket (also known as "ball" ammunition) * Hollow-base bullet, Hollow-base * Hollow-point bullet, Hollow-point * Hydra-Shok * Nosler partition#Early history, Nosler partition * Plastic-tipped bullet, Plastic-tipped * Sabot (firearms), Sabot * Saboted light armor penetrator * Spitzer (bullet), Spitzer * Semiwadcutter * Total metal jacket * Very-low-drag bullet, Very low drag * Wadcutter * Wax bullet, Wax


See also

* List of handgun cartridges * List of rifle cartridges * Table of handgun and rifle cartridges * * *


References


External links


High speed imaging of in flight bullet transition ballistics


* [https://archive.today/20130101212928/http://arizonagunlist.com/ammunition_types.html Arizona Gun List – ammunition types]
Dangerous Game Bullets



Remington Core-Lokt, Bronze Point & Power-Lokt Centerfire Ammunition

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