Introduction to Ammunition

Ammunition, projectiles fired from guns, including their fuzes, primers, and propellant charges. It is used in warfare, for target shooting and hunting, and for ceremonial purposes. In a broad sense, self-contained explosive weapons are also ammunition; they are not discussed in this article, however, but are covered in the articles Bomb; Grenade; Mine; Missiles and Rockets; Torpedo. Also excluded from this article are fireworks and nuclear weapons.

Small-arms Ammunition

Small arms are firearms of .50 caliber (having a barrel with an inside diameter of one-half inch [12.7 mm]) or less—including rifles, pistols, revolvers, and machine guns—and shotguns of all gauges.

A round, or single piece, of fixed ammunition is called a cartridge. It usually consists of a case, a projectile (bullet), a propellant (explosive that propels the bullet), and a primer (explosive that sets off the propellant). It is called fixed ammunition because the case and projectile are attached to each other (fixed) during manufacture and remain so until the round is fired.

The cartridge case, usually of brass or other metal, is a hollow tube that contains smokeless powder or some other propellant. The front end of the case holds the bullet. At the rear is the primer, which in center-fire cartridges is a cap sunk into the center at the rear, and in rimfire cartridges encircles the outer edge of the case. (Some cartridges are made without a case. A caseless cartridge consists of a molded propellant charge with a bullet affixed to one end and a primer to the other.)

The propellant is a relatively slow-burning powder. (An explosive that burns too fast could burst the gun barrel.) Its burning is started by a spark from the primer, which ignites when struck by the firing pin.

The bullet, or projectile, is the part of the cartridge that is fired at the target. Rapidly expanding gases from the burning powder break the bullet loose from the case and propel it through the barrel at high speed. The inner surface of the barrel has spiral grooves (called rifling) that cause the bullet to spin, increasing its stability in flight.

Bullets are made of lead, of lead alloyed with tin or antimony, or of a lead core jacketed with a harder metal. The jacket prevents the lead from contaminating the gun barrel and from breaking apart when it strikes a target. A bullet with an exposed lead point tends to flatten and expand when it strikes, inflicting a severe wound. It is used in rifle ammunition for hunting and in most handgun ammunition intended for self-defense. (This kind of bullet is sometimes called a “dumdum” bullet after the British arsenal at Dum Dum, India, where expanding bullets were made in the 19th century.) By international agreement, expanding bullets are banned from warfare, as are wooden bullets (which splinter) and white-phosphorus bullets (which cause burns).

An armor-piercing bullet has a core of extremely hard material, such as tungsten carbide. Tracer bullets contain a substance that burns and gives off light, aiding the gunner in aiming. Blank ammunition, used in training and for salutes, has a paper, wax, or plastic wad or pellet in place of the bullet.

A cartridge for a shotgun is called a shell. The most common type of shell contains shot—round pellets of lead or steel—instead of a single projectile. The shot is held in a paper or plastic case and separated from the propellant by a wad of paper, plastic, or felt. Some shotgun cartridges use a lead slug instead of shot.

Artillery Ammunition

Artillery includes guns, howitzers, mortars, and missile launchers.

Fixed ammunition, made like the cartridges for small arms, is used in some guns with bore diameters up to 105 millimeters (about 4 inches). In semifixed ammunition, used in some guns of calibers from 75 mm to 120 mm (about 5 inches) and in some 5-inch (127-mm) and 6-inch (152-mm) naval guns, the projectile fits loosely in the case and can be removed to increase or decrease the powder charge. With separate-loading ammunition the projectile is placed in the gun, followed either by a case containing propellant and primer, or by cloth bags of powder and a separate primer.


An artillery projectile made of solid metal is called shot. Several types, known as kinetic-energy projectiles, are designed for penetrating armor plate. These projectiles are made of a dense metal (or with a core of dense metal) and are fired from guns at a very high velocity. Field artillery projectiles range in size from tens of millimeters to a few hundred millimeters, and can weigh from a few pounds (1 kilogram) to hundreds of pounds (hundreds of kilograms).

An artillery projectile that contains an explosive charge is called a shell. A highexplosive shell inflicts damage by the force of the explosion itself, as well as by fragments of the shell casing that scatter widely. One type of projectile designed for use against troops contains bundles of small dartlike fragments called flechettes that scatter in all directions with great force when the shell explodes. Smoke shells contain a chemical used to produce smoke screens. Chemical shells, used in World War I, contained poison gas that was released on impact. Illuminating, or star, shells contain flares attached to parachutes to illuminate targets at night.

Armor-piercing shells are designed primarily for use against tanks. Some, called kinetic-energy shells, use high velocity to penetrate the armor; others, called HEAT shells, use explosives to do so. Armorpiercing incendiary shells are designed to set fires inside tanks. Submunition shells, used mainly against troops, contain explosive devices (usually grenades or mines) that are ejected when the shell lands.

Charges and Fuzes

The explosive charge in an artillery projectile is usually TNT, amatol, a picric-acid compound, or ammonium picrate.

The explosive charge is set off by a fuze. The rotation of the projectile in the gun barrel unlocks the fuze mechanism so that it is “armed” and ready to set off the main charge. The fuze may act directly on the main charge, or, more generally, it may detonate a small quantity of another explosive, such as lead azide. A series of two to four successive split-second explosions (called the explosive train) takes place in the firing of many types of rounds.

Impact fuzes are designed to detonate the projectile on striking an object. Some fuzes contain a short delay element (normally compressed black powder) which allows the shell either to penetrate the target or to ricochet into the air for a fraction of a second before bursting. Time fuzes explode the shell at a preset time after it leaves the gun. Some time fuzes use a mechanical watchlike device; others are operated by the slow burning of a train of compressed black powder. The proximity fuze contains an electronic device that explodes the projectile at a preset distance from the target. Other types of fuzes may be set to detonate the explosive charge at a given altitude.

Primers and Propellants

Artillery is fired by friction primers, in which a strip of metal is drawn through mercury fulminate or some other priming material; by electric primers, ignited by a spark; and by percussion primers like those used on small-arms ammunition. The propellant is usually a slow-burning smokeless powder. Smokeless powders are forms of nitrated cellulose.

The ammunition used in recoilless rifles has a perforated case to allow part of the propellant gases to escape to the rear of the gun, thus eliminating recoil, or “kick.”


Early Artillery Ammunition

Gunpowder, a mixture of sulfur, saltpeter, and charcoal, was known in China as early as the 10th century, but was used mainly in firecrackers. It was being used in war in Europe by the early 14th century, when it was loaded in small cannon to propel stones or the metal darts that had been used in crossbows.

About 1350, balls cast of lead, bronze, or iron came into use. Experiments were made in loading cannon with large numbers of small balls that would scatter over the battlefield. Case shot, or canister, consisted of projectiles of this type placed in a case or can for loading. Canister was in use as early as 1439. It was particularly effective against infantry and cavalry at distances up to 350 yards (320 m). A later form of canister was grape shot, which was effective at ranges up to 1000 yards (900 m). Grape shot consisted of from 9 to 60 iron balls grouped around a frame that would break up and scatter the balls at some distance from the gun.

Both canister and grape were used extensively during the period from the French Revolution through the American Civil War. The mainstay of artillery fire, however, was the cannon ball of solid iron.

Explosive shells were used as early as the 14th century. In the simplest form a cord fuze was inserted in a hole bored in a hollow iron ball. The hollow was filled with gunpowder, the fuze was ignited when the gun was fired, and the bursting charge scattered fragments of the shell. In 1804 Henry Shrapnel, of England, invented spherical case shot—a sphere filled with balls and an explosive charge set off in midair by a time fuze. Spherical case shot came to be called shrapnel. During World War I shrapnel shells were widely used and accounted for most of the wounds inflicted by artillery fire. Although shrapnel has not been in general use since, injuries from shell fragments are still commonly called shrapnel wounds.

Until the mid-19th century all cannon were discharged by applying fire to the powder through a touchhole (a hole bored in the base of the gun's barrel). During the American Civil War a friction primer was introduced. The friction primer was inserted into the touchhole and activated by pulling a lanyard—a long cord attached to the movable part of the primer. Late in the century smokeless powder replaced gunpowder as the propellant for artillery ammunition.

Early Small-arms Ammunition. Ammunition for early small arms consisted of gunpowder and lead balls. It was loaded through the muzzle, or front end, of the barrel. A charge of gunpowder was poured down the barrel and then the ball was pushed down the barrel with a ramrod. With rifled weapons, a small patch of cloth, paper, or leather was placed over the muzzle after the powder was poured in and was rammed down together with the ball. (The patch made the ball fit snugly in the barrel and, when the gun was fired, caused the ball to be spun by the rifling in the barrel.)

Riflemen would carry powder in a flask made of metal or in a horn (usually a cow's horn). They would carry bullets in a pouch and usually have a mold for casting their own bullets from lead. For soldiers, ammunition was often supplied in paper cartridges. Each cartridge contained a bullet and enough powder for one shot. The soldier would tear open a cartridge with his teeth and empty the contents into the barrel.

In firing a gun, gunpowder in the barrel was set off by means of a flash produced by an external priming charge. In early muskets, the priming charge consisted of a small amount of gunpowder placed in a pan located near an opening, or vent, leading to the rear of the barrel. In muskets called matchlocks, which date from the early 1500's, the priming charge was ignited with a mechanism that brought the smoldering end of a taper, or wick, into the pan. In later weapons, such as the wheel lock and flintlock, the powder in the pan was ignited by sparks produced by a mechanism that struck flint against steel. These weapons were replaced in the mid-1800's with guns that were fired with a percussion cap. The cap contained mercury fulminate, an explosive. It was placed over a nipple on a tube leading to the vent. The cap was made to explode by striking it with a moving part called a hammer. The percussion cap was invented in 1807 by Alexander John Forsyth, a Scottish clergyman.

Development of Modern Ammunition

Claude Étienne Minié of France in 1849 produced an elongated bullet—called the Minié ball— that had a hollow base. When the bullet was fired from a gun, the explosion of the propellant forced the sides of the base to expand and tightly grip the rifling as the bullet passed through the barrel. The Minié ball helped increase the accuracy of small arms. Fixed ammunition was developed in the mid-19th century as firearms that were loaded through the breech, or rear of the barrel, became practical. The first smokeless powder practical for military use was developed by Paul Marie Eugè ne Vieille, a Frenchman, in 1887.

Several high explosives were produced by chemists in the 19th century, but because of the dangers in handling, their application to military purposes was slow. Guncotton was invented by Christian Schnbein, a German chemist, in 1846. It became a basic ingredient of smokeless powders. At about the same time Ascanio Sobrero, an Italian, discovered nitroglycerin. It was unsafe to handle until Alfred Nobel of Sweden in 1866 combined it with absorbents to form dynamite. The United States used a “dynamite gun” in the Spanish-American War. Nobel also invented ballistite, a kind of smokeless powder. Picric acid was produced by P. Woulfe in 1771 but was not used as a military explosive until the 1880's.

World War I and After

TNT was first made in 1863 but did not find military use until World War I, when it largely replaced the picric-acid explosives. It is still the most important military explosive.

After World War I a great deal of attention was devoted to the design and composition of projectiles and to the composition of propellants to improve range and accuracy. Many changes were minor—for example, adoption of a “boat-tailed” bullet for .30 caliber rifle ammunition that had less tendency to tumble in flight.

Explosives that became important during World War II include cyclonite, or RDX, and ammonium picrate, or Explosive D. This war also marked the beginnings of the recoilless rifle, the proximity fuze, missile development, and nuclear weapons.

Through the years the trend in the design of ammunition has been toward smaller calibers, permitting lighter-weight weapons. At the same time the goal has been to increase the penetrating power of small-arms ammunition and the destructiveness of artillery ammunition; this has been done through improving propellants, explosive charges, and the metals used for casings and projectiles.

The ball for muzzle-loading rifles was usually of .69 caliber. Early breech-loaders had a caliber of .45 and the rifles used by the U.S. Army in the two World Wars were of caliber .30. After World War II the United States adopted a 7.62 mm rifle cartridge, which is slightly smaller and lighter than the .30 caliber but has greater penetrating power. A high-velocity cartridge of 5.56 mm (about .22 caliber) was designed for the lightweight M-16 rifle, which was adopted by United States military forces in the mid-1960's. The caseless cartridge was also introduced in the 1960's.