Shotshell in the context of "Shot grouping"

A shotgun (also known as a scattergun, peppergun, or historically as a fowling piece) is a long-barreled firearm designed to shoot a straight-walled cartridge known as a shotshell, which discharges numerous small spherical projectiles called shot, or a single solid projectile called a slug. Shotguns are most commonly used as smoothbore firearms, meaning that their gun barrels have no rifling on the inner wall, but rifled barrels for shooting sabot slugs (slug barrels) are also available.

Shotguns come in a wide variety of calibers and gauges ranging from 5.5 mm (.22 inch) to up to 5 cm (2.0 in), though the 12-gauge (18.53 mm or 0.729 in) and 20-gauge (15.63 mm or 0.615 in) bores are by far the most common. Almost all are breechloading, and can be single barreled, double barreled, or in the form of a combination gun. Like rifles, shotguns also come in a range of different action types, both single-shot and repeating. For non-repeating designs, over-and-under and side-by-side break action shotguns are by far the most common variants. Although revolving shotguns do exist, most modern repeating shotguns are either pump action or semi-automatic, and also fully automatic, lever-action, or bolt-action to a lesser extent.

A semi-automatic shotgun is a repeating shotgun with a semi-automatic action, i.e. capable of automatically chambering a new shell after each firing, but requires individual trigger-pull to manually actuate each shot. Semi-automatic shotguns use gas operation, blowback, or recoil operation to cycle the action, eject the empty shell, and load another round. The first semi-automatic shotgun was the Automatic-5 by Browning.

Many semi-automatic shotguns also provide an optional manual means of operation such as by pump action or a charging handle.

A slug is a term used for a bulky solid ballistic projectile. It is "solid" in the sense of being composed of one piece; the shape can vary widely, including partially hollowed shapes. The term is occasionally applied to bullets (just the projectile, never the cartridge as a whole), but is most commonly applied to one-piece shotgun slugs, to differentiate them from shotshells containing numerous shots. Slugs are commonly fired from un-choked smoothbore barrels, but some specially designed slug barrels have riflings that can impart gyroscopic spin required for in-flight stability.

An airgun slug is a type of pellet more recently developed for pre-charged pneumatic airguns. Unlike the conventional diabolo-shaped pellet, which is aerodynamically poor and relies heavily on drag-stabilisation to maintain accuracy, the slug pellet is cylindro-conoidally shaped like a Minié ball and relies predominantly on spin-stabilisation from a rifled barrel. Because of the greater contact area with the barrel bore, these pellets require more power from the gun to overcome the frictional resistance, and therefore are mainly used in PCP airguns, which generally have much higher muzzle energy ratings than other types of airguns such as spring-piston, pump pneumatic or HPA/CO₂ airguns.

Federal Premium Ammunition is a wholly owned subsidiary of the Czechoslovak Group, located in Anoka, Minnesota. With a workforce of nearly 1,500, Federal manufactures shotshell, centerfire, and rimfire ammunition and components.

Garden guns are small bore shotguns commonly used by gardeners and farmers for pest control. They are made to fire small gauges such as .410 bore, .360 bore, 9mm Flobert, and .22 Winchester Magnum Rimfire, or .22 Long Rifle rimfire shotshell cartridges. They are short-range shotguns that can do little harm past 15 to 20 yd (14 to 18 m), and they are relatively quiet when fired with rimfire ammunition. These guns are especially suitable for use inside barns and sheds, as the low-velocity small shot will not penetrate roofs or walls, nor injure livestock with a ricochet. Such guns are also used for pest control at airports, warehouses, stockyards, etc.