A shotgun (also known as a fowling piece or scattergun) is a firearm that is usually designed to be fired from the shoulder, which uses the energy of the explosive in a fixed shell to fire a number of small spherical pellets called shot or a solid projectile. Shotguns come in a wide variety of sizes, ranging from 5.5 mm (.22 inch ) bores up to 5 cm (2 inch) bores, and in a range of firearm operating mechanisms, including breech loading double barreled shotguns, pump-action, bolt-action, lever-action, and semi-automatic models.Since the shot pellets from a shotgun spread upon leaving the barrel, the power of the burning charge is divided among the pellets, which means that the energy of any one ball of shot is fairly low. In a hunting context, this makes shotguns useful primarily for hunting birds and other small game. However, in a military or law enforcement context, the large number of projectiles makes the shotgun useful as a close quarters combat weapon or a defensive weapon. Shotguns are also used for target shooting sports such as skeet, trap, and sporting clay shooting. These involve shooting clay disks, also known as clay pigeons, thrown in various ways.Precursors to the shotgun, such as the musket were widely used by armies in the 18th century. However, in the 19th century, shotgun-type weapons were largely replaced on the battlefield with rifles, which were more accurate over longer ranges. The decline in military use of shotguns reversed in World War I, when American forces used 12-gauge pump action shotguns in close-quarters trench fighting. Since the end of World War II, the shotgun has remained in use with modern armies mostly in specialist roles, such as door breaching or for naval boarding parties. On the other hand, shotguns have become a standard firearm for law enforcement use in many countries. Police often use specialty less-lethal or non-lethal ammunitions, such as tear gas shells, bean bags, stun rounds, and rubber projectiles.