Repeating firearm in the context of Box magazine

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 grenade launcher is a weapon that fires a specially designed, large caliber projectile, often with an explosive, smoke, or gas warhead. Today, the term generally refers to a class of dedicated firearms firing unitary grenade cartridges - for example the widely used 40mm type. The most common type are man-portable, shoulder-fired weapons issued to individuals, although larger crew-served launchers are issued at higher levels of organization by military forces.

Grenade launchers are produced in the form of standalone weapons (either single shot or repeating) or as attachments mounted to a parent firearm, usually a rifle. Larger crew-served automatic grenade launchers such as the Mk 19 are mounted on tripods or vehicles.

A handgun is a firearm designed to be usable with only one hand. It is distinguished from a long barreled gun (i.e., carbine, rifle, shotgun, submachine gun, or machine gun) which typically is intended to be held by both hands and braced against the shoulder. Handguns have shorter effective ranges compared to long guns, and are much harder to shoot accurately. While most early handguns are single-shot pistols, the two most common types of handguns used in modern times are revolvers and semi-automatic pistols.

Before commercial mass production, handguns were often considered a badge of office — comparable to a ceremonial sword – as they had limited utility and were more expensive than the long barreled guns of the era. In 1836, Samuel Colt patented the Colt Paterson, the first practical mass-produced revolver, which was capable of firing five shots in rapid succession and quickly became a popular personal weapon, giving rise to the saying, "God created men, but Colt made them equal."

A repeating rifle is a single-barreled rifle capable of repeated discharges between each ammunition reload. This is typically achieved by having multiple cartridges stored in a magazine (within or attached to the rifle) and then fed individually into the chamber by a reciprocating bolt, via either a manual or automatic action mechanism, while the act of chambering the round typically also recocks the hammer/striker for the following shot. In common usage, the term "repeating rifle" most often refers specifically to manual repeating rifles (e.g. lever-action, pump-action, bolt-action, etc.), as opposed to self-loading rifles, which use the recoil, gas, or blowback of the previous shot to cycle the action and load the next round, even though all self-loading firearms are technically a subcategory of repeating firearms.

Repeating rifles were a significant advance over the preceding single-shot, breechloading rifles when used for military combat, as they allowed a much greater rate of fire. The repeating Henry rifle was used by the infantry and Spencer rifle was used by the cavalry during the American Civil War and the subsequent American Indian Wars, and the first repeating air rifle to see military service was the Windbüchse rifle.

An infantry square, also known as a hollow square or square formation, was a musket-era historic close order formation used in combat by infantry units, usually when threatened with cavalry attack. To deploy its weapons effectively, a traditional infantry unit would generally form a line; but the line was vulnerable to more nimble cavalry, which could sweep around the end of the line, or burst through it, and then attack the undefended rear or simply sweep along the line attacking the individual footsoldiers successively. By arranging the unit so that there was no undefended rear or flank, an infantry commander could organise an effective defense against cavalry attack. With both the development of modern repeating firearms and the demise of cavalry in warfare, the square formation is considered obsolete and is effectively never used in modern day warfare.

A revolver is a repeating handgun with at least one barrel and a revolving cylinder containing multiple chambers (each holding a single cartridge) for firing. Because most revolver models hold six cartridges before needing to be reloaded, revolvers are commonly called six shooters or sixguns. Due to their rotating cylinder mechanism, they may also be called wheel guns.

Before firing, cocking the revolver's hammer partially rotates the cylinder, indexing one of the cylinder chambers into alignment with the barrel, allowing the bullet to be fired through the bore. By sequentially rotating through each chamber, the revolver allows the user to fire multiple times until having to reload the gun, unlike older single-shot firearms that had to be reloaded after each shot.

In firearms, the cylinder is the cylindrical, rotating part of a revolver containing multiple chambers, each of which is capable of holding a single cartridge. The cylinder rotates (revolves) around a central axis in the revolver's action to sequentially align each individual chamber with the barrel bore for repeated firing. Each time the gun is cocked, the cylinder indexes by one chamber (for five-chambers, by 72°, for six-chambers, by 60°, for seven-chambers, by 51.43°, for eight-chambers, by 45°, for nine-chambers, by 40°, and for ten-chambers, by 36°). Serving the same function as a rotary magazine, the cylinder stores ammunitions within the revolver and allows it to fire multiple times, before needing to be reloaded.

Typically revolver cylinders are designed to generally hold six cartridges (hence revolvers sometimes are referred to as six-guns or six-shooters), but some small-frame concealable revolvers such as the Smith & Wesson Model 638 have a 5-shot cylinder, due to the smaller overall size and limited available space. The Nagant M1895 revolver has a 7-shot cylinder, the Webley-Fosbery Automatic Revolver has an 8-shot cylinder in .38 ACP, the LeMat Revolver has a 9-shot cylinder, and the Smith & Wesson Model 617 has a 10-shot cylinder in .22 Long Rifle.

A semi-automatic pistol (also called a self-loading pistol, autopistol, or autoloading pistol) is a repeating handgun that automatically ejects and loads cartridges in its chamber after every shot fired, but only one round of ammunition is fired each time the trigger is pulled. The pistol's fire control group disconnects the trigger mechanism from the firing pin/striker until the trigger has been released and reset manually, unlike the self-cycled firing mechanism in fully automatic pistols.

A semi-automatic pistol recycles part of the energy released by the propellant combustion to move its bolt, which is usually housed inside the slide. After a round of ammunition is fired, the spent cartridge casing is extracted and ejected as the slide/bolt moves rearwards under recoil, the hammer/striker is cocked by the slide/bolt movement, and a new round from the magazine is pushed into the chamber when the slide/bolt returns forward under spring tension. This sets up the following shot (i.e. "in battery"), which is fired as soon as the trigger is pulled again. Most pistols use a short recoil operation to perform this, but some pistols use simple blowback or gas operation mechanisms.

In firearm designs, the term single-shot refers to guns that can hold only a single round of ammunition inside and thus must be reloaded manually after every shot. Compared to multi-shot repeating firearms ("repeaters"), single-shot designs have no moving parts other than the trigger, hammer/firing pin or frizzen, and therefore do not need a sizable receiver behind the barrel to accommodate a moving action, making them far less complex and more robust than revolvers or magazine/belt-fed firearms, but also with much slower rates of fire.

The history of firearms began with muzzleloading single-shot firearms such as the hand cannon and arquebus, then multi-barreled designs such as the derringer appeared, and eventually many centuries passed before breechloading repeating firearms became commonplace. Although largely disappeared from military usage due to insufficient firepower, single-shot firearms are still produced by many manufacturers in both muzzleloading and cartridge-firing varieties, from zip guns and ultra-concealable pocket pistols to the highest-quality hunting and match rifles.

A lever action is a type of action for repeating firearms that uses a manually operated cocking handle located around the trigger guard area (often incorporating it) that pivots forward to move the bolt via internal linkages, which will feed and extract cartridges into and out of the chamber, and cock the firing pin mechanism. This contrasts to other type of repeating actions such as the bolt-action, pump-action, semi-automatic, fully automatic, and/or burst mode actions. A firearm using this operating mechanism is colloquially referred to as a levergun.

Most lever-action firearms are rifles, but some lever-action shotguns and a few pistols have been made. The Winchester Model 1873 rifle is one of the most famous lever-action firearms, but many manufacturers (notably Henry Repeating Arms and Marlin Firearms) also produce lever-action rifles. Colt produced the 6403 lever-action Colt-Burgess rifles from 1883 until 1885 and Mossberg formerly produced the Model 464 rifle.

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.

Bolt action is a type of manual firearm action that is operated by directly manipulating the turn-bolt via a bolt handle, most commonly placed on the right-hand side of the firearm (as most users are right-handed). The majority of bolt-action firearms are rifles, but there are also some variants of shotguns and handguns that are bolt-action.

Bolt action firearms are generally repeating firearms, but many single-shot designs are available as well, particularly in shooting sports where single-shot firearms are mandated, such as most Olympic and ISSF rifle disciplines.

A bolt is the part of a repeating, breechloading firearm that blocks the rear opening (breech) of the barrel chamber while the propellant burns, and moves back and forward to facilitate loading/unloading of cartridges from the magazine. The firing pin and extractor are often integral parts of the bolt. The terms "breechblock" and "bolt" are often used interchangeably or without a clear distinction, though usually, a bolt is a type of breechblock that has a nominally circular cross-section.

In most automatic firearms that use delayed blowback, recoil, or gas operation, the bolt itself is housed within the larger bolt carrier group (BCG), which contains additional parts that receives rearward push from a gas tube (direct impingement) or a gas piston (short-stroke or long-stroke piston) system. The slide of a self-loading pistol contains the same components and serves similar functions.

A semi-automatic firearm, also called a self-loading or autoloading firearm (fully automatic and selective fire firearms are also variations on self-loading firearms), is a repeating firearm whose action mechanism automatically loads a following round of cartridge into the chamber and prepares it for subsequent firing, but requires the shooter to manually actuate the trigger in order to discharge each shot. Typically, this involves the weapon's action utilizing the excess energy released during the preceding shot (in the form of recoil or high-pressure gas expanding within the bore) to unlock and move the bolt, extracting and ejecting the spent cartridge case from the chamber, re-cocking the firing mechanism, and loading a new cartridge into the firing chamber, all without input from the user. To fire again, however, the user must actively release the trigger, and allow it to "reset", before pulling the trigger again to fire off the next round. As a result, each trigger pull only discharges a single round from a semi-automatic weapon, as opposed to a fully automatic weapon, which will shoot continuously as long as the ammunition is replete and the trigger is kept depressed.

Ferdinand Ritter von Mannlicher produced the first successful design for a semi-automatic rifle in 1885, and by the early 20th century, many manufacturers had introduced semi-automatic shotguns, rifles and pistols.

A magazine, often simply called a mag, is an ammunition storage and feeding device for a repeating firearm, either integral within the gun (internal or fixed magazine) or externally attached (detachable magazine). The magazine functions by holding several cartridges within itself and sequentially pushing each one into a position where it may be readily loaded into the barrel chamber by the firearm's moving action. The detachable magazine is sometimes colloquially referred to as a "clip," although this is technically inaccurate since a clip is actually an accessory device used to help load ammunition into the magazine or cylinder of a firearm.

Magazines come in many different shapes and sizes from integral tubular magazines on lever-action and pump-action rifles and shotguns that may hold more than 5 rounds to detachable box magazines and drum magazines for automatic rifles and light machine guns that may hold more than 50 rounds. Various jurisdictions ban what they define as "high-capacity magazines".

John Moses Browning (January 23, 1855 – November 26, 1926) was an American firearm designer who developed many varieties of military and civilian firearms, cartridges, and gun mechanisms, many of which are still in use around the world. He made his first firearm at age 13 in his father's gun shop and was awarded the first of his 128 firearm patents on October 7, 1879, at the age of 24. He is regarded as one of the most successful firearms designers of the 19th and 20th centuries and a pioneer of modern repeating, semi-automatic, and automatic firearms.

Browning influenced nearly all categories of firearms design, especially the autoloading of ammunition. He invented, or made significant improvements to, single-shot, lever-action, and pump-action rifles and shotguns. He developed the first reliable and compact autoloading pistols by inventing the telescoping bolt, then integrating the bolt and barrel shroud into what is known as the pistol slide. Browning's telescoping bolt design is now found on nearly every modern semi-automatic pistol, as well as several modern fully automatic weapons. He also developed the first gas-operated firearm, the Colt–Browning Model 1895 machine gun – a system that surpassed mechanical recoil operation to become the standard for most high-power self-loading firearm designs worldwide. He also made significant contributions to automatic cannon development.