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.
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.
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.