Bullet - Materials

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.

• Lead: Simple cast, extruded, swaged, or otherwise fabricated lead slugs are the simplest form of bullets. At speeds of greater than 300 m/s (1000 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 too does not solve the problem at higher velocities.
• 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 Teflon have been used, with limited success; however, hollow point bullets with plastic aerodynamic tips have been very successful at both improving accuracy and enhancing expansion.
• Blanks: 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. Note that blank cartridges, at short ranges, can be as lethal as regular cartridges due to the force of the expanding gas - numerous tragic accidents have occurred with blank cartridges (e.g., the death of actor Jon-Erik Hexum).
• Practice: Made from lightweight materials like rubber, 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.
• Less lethal, or Less than Lethal: Rubber bullets, plastic bullets, and beanbags are designed to be non-lethal, for example 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: These bullets are made with an explosive or flammable mixture in the tip that is 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 itself.

• 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 a cavity filled with a small amount of low explosive depending on the velocity and deformation upon impact to detonate.
• Tracer: These have a hollow back, filled with a flare material. Usually this is a mixture of magnesium metal, 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. Such ammunition is useful to the shooter as a means of learning how to point shoot moving targets with rifles. This type of round is also used by all branches of the 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 and is intended to show where you are firing so friendly forces can engage the target as well. The flight characteristics of tracer rounds differ from normal bullets due to their lighter weight.
• 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.
• Nontoxic shot: Steel, bismuth, tungsten, and other exotic bullet alloys prevent release of toxic lead into the environment. Regulations in several countries mandate the use of nontoxic projectiles especially when hunting waterfowl. 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 lead poisoning by constant grinding of lead pellets against food means lead poisoning effects are magnified. Such concerns apply primarily to shotguns, firing pellets (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 (RoHS) legislation has also been applied to bullets on occasion to reduce the impact of lead on the environment at shooting ranges. United States Environmental Protection Agency announced that the agency does not have the legal authority to regulate this type of product (lead bullets) under the Toxic Substances Control Act (TSCA), nor is the agency seeking such authority. NRA-ILA :: EPA Denies Ammo Ban Petition With some nontoxic shot, e.g., steel shot, care must be taken to shoot only in shotguns (and with chokes) specifically designed and designated for steel shot; for other, particularly older, shotguns, serious damage to the barrel and chokes can occur. And, because steel is lighter and less dense than lead, larger sized pellets must be used, thus reducing the number of pellets in a given charge of shot and possibly limiting patterns on the target; other formulations, e.g. bismuth, do not present this disability.
• Blended-metal: Bullets made using cores from powdered metals other than lead with binder or sometimes sintered.
• 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.
• Solid or 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 copper nickel, tellurium copper and brass like highly machinable UNS C36000 Free-Cutting Brass. Often these projectiles are turned on precision 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 which do not allow rifles (because a missed slug shot will travel considerably less far than a rifle bullet).