Artillery

Aircraft artillery protects troops and military installations from air attack. A Vulcan 20-millimetre cannon, has six rotating barrels and can fire over a ton of shells per minute.

Field artillery, such as the howitzer shown above, support in­fantry and armoured forces. These weapons, which range from 75 to 125 millimetres, can be transported by truck or helicopter.

Chaparral missiles, are guided missiles used against low-flying aircraft. They pick up heat waves given off by a target and automatically head toward the target.

A self-propelled howitzer, can be driven without being towed. This 155-millimetre howitzer can fire 43-kilogram shells about 15 kilometres.

HAWK missiles, can attack aircraft flying as low as 30 metres. The HAWK uses a radar echo from its target to locate the target. These missiles are 3.7 metres long.

Artillery includes mounted guns or rocket launchers that are too large or too heavy to be classed as small arms. As a general rule, any gun or launcher that uses ammunition 2.5 centimetres or more in diameter and that is not fired from the hand or shoulder may be called artillery.

Parts of a gun

An artillery piece consists of a barrel (tube) with two openings. The opening where the shell comes out is the muzzle. The breech is the opening where the ammuni­tion is inserted. The weapon's size is given in terms of its calibre (diameter of the bore or ammunition). The breechblock closes the breech and usually contains the firing pin or firing mechanism.

Guns may have either a rifled or a smooth bore. Rifled bores have spiralled grooves that spin and steady the shell, so it will travel nose-first to the target. Smooth­bore guns use ammunition with fins that steady the shells in flight. The firing mechanism contains a primer for large calibre guns, or a firing pin for smaller weap­ons. The primer ignites the propellant in the ammuni­tion. The propellant develops a very high pressure that forces the projectile out of the muzzle at high velocity (speed).

Kinds of artillery

Artillery is classified according to size as light artil­lery, medium artillery, and heavy artillery. It may also be classified by the trajectory (curved path of flight) it im­parts to the projectile. Guns use a low, flat trajectory at high muzzle velocity. Howitzers use a high arc trajectory against targets hidden behind obstacles.

Mortars, rocket launchers, and recoilless rifles are often considered artillery. Mortars usually have a smooth bore and are loaded from the muzzle. They send projectiles in higher arc trajectories than howitzers. Rocket launchers start the rockets on their flights. Re- coilless rifles fire shells the size of small calibre artillery shells. They are much lighter than other artillery weap­ons. These rifles may be carried by hand or mounted on vehicles.

Field artillery is used to support infantry and ar­moured forces. The weapons may be towed by tractors or trucks or mounted on vehicles so they can be brought into action quickly. They vary in size from guns firing 0.5-kilogram projectiles to those firing 159- kilogram projectiles. Ammunition trailers and tractors have replaced the caissons (ammunition wagons) that were once used to carry ammunition for field artillery Weapons ranging from 75 to 125 millimetres are mounted on tanks and tank destroyers. Surface to surface guided missiles supplement field artillery.

Antiaircraft artillery can fire shells rapidly at high angles. The guns are usually aimed at the target by electronic automatic fire control systems. Generally, special fuses are used to explode the shells in the area of the  target. Antiaircraft guns are often supported by surface to air missiles. See Antiaircraft defence.                

Other artillery. Cannon mounted in aeroplane and helicopters and on naval vessels are sometimes called artillery. See Air Force; Cannon; Warship.

How artillery is made

Until the mid-1800's, almost all cannon were cast in brass, bronze, or cast iron. To make the cannon stronger, manufacturers added more metal to make the barrel walls thicker.

Later in the 1800's, manufacturers made larger guns by forging. In forging, workers melt the steel in a furnace, then pour it into a gun or ingot mould to cool. They reheat the metal to about 1150° C and use hydraulic hammers or presses to forge it into shape.

The mono-block process. Most gun tubes today are made by the mono-block method because of the development of high-strength steels. By this process, manufacturers make the tube stronger by expanding it under internal pressure until the interior diameter of the tube has been permanently enlarged. The outer layers of metal tend to shrink to their original dimensions when the pressure is released, but the inner layers tend to keep their enlarged diameter. This compresses the inner layers. This process is also called cold working or autofrettage. After the tube has been formed, it is annealed (tempered) by being heated and slowly cooled. Workers then machine it to its final specifications.

Rifling. After final machining, the gun is rifled. In this process, workers cut grooves in the finished bore surface of the gun. Instead of cutting these grooves directly into the barrel, workers sometimes cut them into a separate tube called a liner, which can be inserted into the barrel. One advantage of a rifled liner is that it can be placed with a new liner when it becomes worn. But higher construction costs have limited their use.

History

Artillery was first used during the 1300's. The French used small cannon against the English in 1450, and Ottoman Turks under Muhammad II used artillery in the final campaign to capture Constantinople in 1453. From these early beginnings, guns have increased enormously in size, firepower, and accuracy. Artillery played an increasing part in battles. Napoleon was the first general to collect his artillery in a grande batterie (big battery).

He concentrated his artillery fire on one point in the enemy's line, and then sent troops against that point.

During World War I (1914-1918), troops on the Western Front dug great mazes of trenches and fought from fairly fixed positions. Much of the fighting consisted of exchanges of fire between big-gun batteries. In 1918, the Germans shelled Paris with "Paris Guns." These huge guns hurled shells 24.9 kilometres above the surface the earth toward a target up to 120 kilometres away.

Giant guns had little place in World War II (1939-1945). They could not move fast enough to keep up with the rapid changes in battle lines. Aeroplanes could easily destroy fixed batteries of large guns. The greatest artillery advances during the war were in the power and mobility  of smaller weapons. Helicopters now carry artillery into battle in a procedure known as airmobility. On May 29,1953, the United States fired the first atomic artillery shell from a 280-millimetre cannon. Today, artillery weapons of smaller calibres can fire atomic projectiles.

Related articles: Ammunition, Antiaircraft defence, Ballistics, Cannon, Firearm, Guided missile, Gun, Mortar, Range finder, Shrapnel, Tank, World War I, and World War II.