The earliest version of a gun can be traced to china in the mid 10th century, the Chinese had discovered gunpowder in the 9th century and the first models of guns were bamboo or wooden tubes, tied to the end of spears that would spray out fire and eventually shrapnel was added to act as a projectile. Soon the composition of gunpowder changed and more saltpeter was added. This made gunpowder have a greater explosive force, thus bamboo and wooden tubes would not do as barrels.
With the explosive force of gunpowder greatly increased, metal was now used for the tube or barrel. Also shrapnel was no longer used and projectiles made of metal were fashioned to closer fit the barrel and maximize the explosive force of the gunpowder. This was the beginning of the modern gun as three essential things were achieved, namely; a metal barrel, a metal projectile that fully occludes the muzzle and high nitrate gunpowder. From here the development of the first smooth bore fire arm began. There are two main components to a gun or firearm. First is the barrel, there are two types of barrel, a smooth bore barrel is one which has no need to stabilize the trajectory of the projectile. The second type of barrel is a rifled barrel. This is where grooves are carved inside the barrel to create an artificial spin to stabilize the projectile as it leaves the muzzle of the gun. The size of the projectile and the diameter of the barrel are used to identify various types of guns. Usually it is the bore or the internal diameter of the barrel that is used to report the size or caliber of the gun. This measurement is usually given in the form of fractions of an inch or as millimeters. The projectile is the second essential part of a gun, it can be a single bullet, which is simple or it could also carry a payload for example a shotgun shell or explosive shell.
The Gatling gun was the first rapid fire gun, it was invented b Richard Gatling, and was used during the American Civil war by the Union Soldiers. Further developments to guns are the invention of the first sub machine gun, the MP18.1, during World War I. Theodor Bergman, designed a fully automatic gun that could be operated by one soldier and fired single pistol cartridges. They were mainly used by German assault troops. From here the design, efficiency and capabilities of guns have advanced a lot, both as personal firearms and for military use.
The types of guns available today fall into several categories, from Military guns, such as; assault rifles, carbines, sniper rifles and shot guns. There are also several types of machine gun, the first one invented being the Gatling gun, metal storm, sub machine gun and machine pistol, are also other types of machine guns. Other types of guns are, hand guns, auto-canons and artillery guns.