Characteristics of ShotGuns
Shotguns come in a wide variety of forms, from rimfire models with .22 inch (5.5 mm), bores up to massive punt guns with 2 inch (5 cm) bores, and in nearly every type of firearm operating mechanism. The common characteristics that make a shotgun unique center around the requirements of firing shot. These features are the features typical of a shotgun shell, namely a relatively short, wide cartridge, with straight walls, and operating at a relatively low pressure.
Ammunition for shotguns is referred to in the USA as shotgun shells, shotshells, or just shells (when it is not likely to be confused with artillery shells). The term cartridges is standard usage in the United Kingdom. Single projectile loads are generally called shotgun slugs or just slugs.
The shot pellets from a shotgun spread upon leaving the barrel which makes it easier to hit small targets at suitable ranges than with a rifle. The shot is usually fired from a smoothbore barrel; another configuration is the rifled slug barrel, which is used to fire a single projectile (though some slugs can also be fired from smoothbore weapons).
Since the power of the burning charge is divided among the pellets, the energy of any one ball of shot is fairly low, making shotguns useful primarily for hunting birds and other small game. However, the large number of projectiles makes the shotgun useful as a close-combat weapon or defensive weapon, where the short range ensures that many of the projectiles of shot will hit the target (see riot shotgun and combat shotgun).