Editing Bullet (section)

==Materials==
[[Image:Halvmantlad.jpg|thumb|[[Expanding bullet]] loaded in a [[6.5×55mm]] before and after expanding. The long base and small expanded diameter show that this is a bullet designed for deep penetration on [[large game]]. The bullet in the photo traveled more than halfway through a moose before coming to rest, performing as designed.]]

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&nbsp;m/s (1,475&nbsp;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&nbsp;ft/s) (common in most [[handgun]]s), 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]] alloys, or [[steel]]; 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 bullet]]s, are making their way into the market.
[[File:3CastBullets.png|thumb|Hard cast solid bullet (left), with gas check (center) and lubrication (right)]]
[[File:Cartridge cross section.svg|thumb|A modern [[centerfire]] [[Cartridge (firearms)|''cartridge'']] consisting of the following:

''1.'' ''bullet'',  as the [[projectile]]; ''2.'' ''metallic'' [[Cartridge (firearms)|''case'']], which holds all parts together;

''3.'' ''propellant'', for example [[gunpowder]] or [[cordite]];''4.'' ''rim'', which provides the extractor on the firearm a place to grip the case to remove it from the chamber once fired;

''5.'' [[Primer (firearms)|''primer'']], which ignites the propellant.]]
* ''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 bullet]]s, [[plastic bullet]]s, 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 gun]]s and in [[anti-materiel rifle]]s.
* ''[[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]]. A pointed tip is often used, but a flat tip on the penetrator portion is generally more effective.<ref>{{cite book | last = Hughes | first = David | title = The History and Development of the M16 Rifle and Its Cartridge | publisher = Armory Pub | location = Oceanside | year = 1990 | isbn = 978-0-9626096-0-2 }}</ref>
* ''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 [[gizzard]]s 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.<ref>{{cite web|title=Research—Eagles and Lead.|url=http://www.soarraptors.org/leadresearch.html|publisher=SOAR Raptor Foundation}}</ref> Reduction of hazardous substances legislation has also been applied to bullets on occasion to reduce the impact of lead on the environment at [[shooting range]]s. 
* ''[[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.<ref>{{cite book |first1=Nikos |last1=Passas |first2=Neva |last2=Goodwin |year=2005 |title=It's Legal but It Ain't Right: Harmful Social Consequences of Legal Industries (Evolving Values For A Capitalist World) |publisher=University of Michigan Press |doi=10.3998/mpub.11472}}</ref> These bullets are often made with a [[lead]] core and a [[copper]] jacket, though variations like MRX bullets have [[tungsten]] in its core.<ref>{{cite web |url=https://www.samaterials.com/content/characteristics-of-advanced-tungsten-bullets.html |title=Characteristics of Advanced Tungsten Bullets |last=Trento |first=Chin |date=Apr 12, 2024 |website=Stanford Advanced Materials |access-date=Aug 16, 2024}}</ref> The [[polymer]] tip in expanding bullets is designed to enhance [[aerodynamics]] for shooting at flat long-range trajectories.<ref>{{cite book |author=Brian J. Heard |year=2013 |title=Forensic Ballistics in Court: Interpretation and Presentation of Firearms Evidence |publisher=Wiley |page=320 |isbn=978-1-118-50501-4}}</ref>