A gun is a weapon that fires bullets from a tube called a barrel. First some explosive is filled then the bullet is placed inside the barrel. A spiral groove cut in the gun barrel make the shells spin as they flow through the air. When the explosive is ignited, it produces large amounts of hot gases. These hot gases expand very quickly and hit the bullet. The force brings out the bullet from the barrel at a very high speed. Although it cannot be accepted as proven, it is believed that the earliest guns were manufactured both in China and in North Africa in 1250 AD.
The earliest representation of an English Gun is contained in an illustrated manuscript dated 1326 AD available in an Oxford Library.
The heavy cannons were first used in about 1350 AD. They were mounted on a wooden support. A gunner placed some gunpowder in the open end of the barrel, called the muzzle. He then rammed it down deep into the closed end called the breech. Then he put a cannon ball next to the powder into the barrel. The gun was fired by placing a lighted wick into a hole in the breech. The wick ignited the gunpowder and the cannon were fired. Sawai Jai Singh, the ruler of Jaipur, commissioned cannon on wheels in 1720 which is the largest cannon on wheels in the world. Named as Jaivana, this had a 20 ft. long barrel and weighed 50 tonnes; it required 100 kg gunpowder for a single shot and had a range of 35 km.
During the 16th century, pistols and other sorts of guns became common but all these were loaded from the muzzle. In 1800 came guns which fired pointed shells that exploded when they hit their targets. During the 19th century, a different kind of gun was invented. This gun was loaded from the back and instead of a metal ball, cartridges were used in it. The cartridges were placed near the back of the gun.
A cartridge has a metal or paper tube containing a bullet and some powder. This was enclosed by a cap. The cap lies at the back of the cartridge. It contains a small amount of explosive. This explosive is very sensitive and is exploded by striking it with a firing pin. This explosion gives a jolt to the bullet and it comes out. By the 19th century, breech loading rifles and pistols were in general use.
In 1835, an American inventor, Samuel Colt invented a pistol which when fired threw out a revolving bullet. So, he called it a revolver. It contained a chamber that held five or six cartridges. When the trigger was pulled, the chamber turned round and lined up a cartridge with the barrel. Modern revolvers are very similar to those made by Colt.
During the 19th century, rifles became popular. Now they came to be fitted with magazines to hold cartridges. These rifles had a bolt beside the breech. These rifles were used on a very large scale during the two World Wars. Inventors developed Muskets Rifles and machine guns for long distance shooting during the end of 2nd World War.
These were automatic light guns that kept on firing bullets as long as the trigger was pressed. After this, heavy guns known as field guns were developed. Modern field guns weigh about four tonnes. Shells used in these weigh about 40 kg and have a range of about 14 km. The barrels are made of the highest grade of steel and these guns are very expensive. In modern guns a hammer set off an explosion that drives a shell or bullet from the barrel.