Bullet A bullet is a projectile propelled by a firearm , sling , or air gun . Bullets do not normally contain explosive s , but damage the intended target by impact and penetration . The word " bullet " is sometimes colloquially used to refer to ammunition in general , or to a cartridge , which is a combination of the bullet , case / shell , powder , and primer . This use of ' bullet ' , when ' cartridge ' is intended , leads to confusion when the components of a cartridge are discussed or intended . See the reference section for more detail . History . The history of bullets far predates the history of firearms . Originally , bullets were made out of metal , stone or purpose - made clay balls used as sling ammunition , as weapon s and for hunting . Eventually as firearm s were developed , these same items were placed in front of a propellant charge of gunpowder at the end of a closed tube . As firearms became more technologically advanced , from 1500 to 1800 , bullets changed very little . They remained simple " round " ( spherical ) lead balls , called " rounds " , differing only in their diameter . The development of the hand culverin and matchlock arquebus brought about the use of cast lead balls as projectiles . " Bullet " is derived from the French word " boulette " which roughly means " little ball " . The original musket bullet was a spherical lead ball smaller than the bore , wrapped in a loosely fitted paper patch which served to hold the bullet in the barrel firmly upon the powder . ( Bullets that were not firmly upon the powder upon firing risked causing the barrel to explode , with the condition known as a " short start " . ) The loading of muskets was , therefore , easy with the old smooth - bore Brown Bess and similar military muskets . The original muzzle - loading rifle , on the other hand , with a more closely fitting ball to take the rifling grooves , was more difficult to load , particularly when the bore of the barrel was fouled from previous firings . For this reason , early rifles were not generally used for military purposes . The first half of the nineteenth century saw a distinct change in the shape and function of the bullet . In 1826 , Delvigne , a French infantry officer , invented a breech with abrupt shoulders on which a spherical bullet was rammed down until it caught the rifling grooves . Delvigne ' s method , however , deformed the bullet and was inaccurate . Square bullets , invented by James Puckle and Kyle Tunis , were briefly used in one version of the Puckle gun . The use of these was soon discontinued due to irregular and unpredictable flight patterns . Pointed bullets . Among the first pointed or " conical " bullets were those designed by Captain John Norton of the British Army in 1823 . Norton ' s bullet had a hollow base which upon 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 . It was very similar to Norton ' s bullet except that the hollow base of the bullet was fitted with a wooden plug which more reliably forced the base of the bullet to expand and catch the rifling . Tests proved that Greener ' s bullet was extremely effective but it too was rejected for military use because , being two parts , it was judged as being too complicated to produce . The soft lead Minié ball was first introduced in 1847 by Claude - Étienne Minié , a captain in the French Army . It was nearly identical to the Greener bullet . As designed by Minié , the bullet was conical in shape with a hollow cavity in the rear , which was fitted with a little iron cap instead of a wooden plug . When fired , the iron cap would force 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 1855 , the British adopted the Minié ball for their Enfield rifles . A similar bullet called the Nessler ball was also developed for smoothbore muskets . The small Minié ball first saw widespread use in the American Civil War . Roughly 90 % of the battlefield casualties in this war were caused by Minié balls fired from rifles . Between 1854 and 1857 , Sir Joseph Whitworth 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 , when it was gradually superseded by Metford ' s . About 1862 and later , W . E . Metford carried out an exhaustive series of experiments on bullets and rifling , and 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 ( 0 . 303 " , 7 . 70 mm ) rifle , Mark I , was finally adopted for the British army . The Lee - Metford was the predecessor of the Lee - Enfield . The modern bullet . The next important change in the history of the rifle bullet occurred in 1882 , when Major 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 . 5mm and 8mm ) and it is the precursor of the 8mm " Lebel bullet " which was adopted for the smokeless powder ammunition of the Mle 1886 Lebel rifle . The surface of lead bullets fired at high velocity may melt due to hot gases behind and friction with the bore . Because copper has a higher melting point , and greater specific heat capacity and hardness , copper jacketed bullets allow greater muzzle velocities . European advances in aerodynamics led to the pointed spitzer bullet . By the beginning of the twentieth century , most world armies had begun to transition to spitzer bullets . These bullets flew for greater distances more accurately and carried more energy with them . Spitzer bullets combined with machine gun s greatly increased the lethality of the battlefield . The latest advancement in bullet shape was the boat tail , a streamlined base for spitzer bullets . The vacuum created as air moving at high speed passes over the end of a bullet slows the projectile . The streamlined boat tail design reduces this 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 " from its inventor ( a lieutenant - colonel Desaleux ) , was introduced as standard military ammunition in 1901 , for the French Lebel Model 1886 rifle . 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 which will form this seal without causing 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 . With smooth - bore firearms , a spherical shape was optimum because no matter how it was oriented , it presented a uniform front . These unstable bullets tumbled erratically and provided 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 . Another method of stabilization is for the center of mass of the bullet to be as far forward as is practical , which is how the Minié ball and the shuttlecock are designed . This allows the bullet to fly front - forward by means of aerodynamics . See the articles on terminal ballistics and / or stopping power for an overview of how bullet design affects 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 , and the velocity and physical characteristics of the bullet itself . Bullets are generally designed to penetrate , deform , and / or break apart . For a given material and bullet , the strike velocity is the primary factor determining which outcome is achieved . Bullet shapes are many and varied , and an array of them can be found in any reloading manual that sells bullet moulds . Mould manufacturers such as RCBS , Paul Jones Moulds , and David Mos offer many different calibers and designs . With a mould , bullets can be made at home for reloading one ' s own 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 hand loading and are much more convenient than casting bullets from bulk lead . Propulsion . Propulsion of the ball can happen via several methods : Materials . Bullets for black powder , or muzzle loading firearms , were classically molded from pure lead . This worked well for low speed bullets , fired at velocities of less than 450 m / s ( 1475 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 ) works very well . For even higher speed bullet use , jacketed coated 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 . Treaties and prohibitions . The St . Petersburg Declaration of 1868 prohibited the use of explosive projectiles weighing less than 400 grams . The Hague Convention prohibits certain kinds of ammunition for use by uniformed military personnel against the uniformed military personnel of opposing forces . These include projectiles which explode within an individual , poisoned and expanding bullets . Protocol III of the 1983 Convention on Certain Conventional Weapons , an annexe to the Geneva Conventions , prohibits the use of incendiary munitions against civilians . Nothing in these treaties prohibits tracers or the use of prohibited bullets on military equipment . These treaties apply even to . 22 LR bullets used in pistols , rifles and machine guns . Hence , the High Standard HDM pistol , a . 22 LR suppressed pistol , had special bullets developed for it during World War II that were full metal jacketed , in place of the soft - point and hollow - point bullets that are otherwise ubiquitous for . 22 LR rounds . Some jurisdictions are acting on environmental concerns and banning hunting with lead shotgun pellets . This creates issues for shooters because stainless steel pellets are considered to behave sub - optimally in flight compared to lead . The element bismuth is a safe alternative whose density is closer to lead than steel , and ammunition made from it is becoming ever more widely available .