A firearm is any type of gun that shoots projectiles using high explosive pressure generated from combustion (deflagration) of chemical propellant, most often black powder in antique firearms and smokeless powder in modern firearms. Small arms is a subset of light firearms that is designed to be readily carried and operated by an individual. The term "firearm" is however variably defined both technically and legally in different countries (see legal definitions), and can be used colloquially (sometimes incorrectly) to refer to any type of guns including air guns. The first firearms originated in 10th-century Song dynasty China (see gunpowder weapons in the Song dynasty), when bamboo tubes containing gunpowder and pellet projectiles were mounted on spears to make the portable fire lance, which was operable by a single person and was later used effectively as a shock weapon in the siege of De'an in 1132. In the 13th century, fire lance barrels were replaced with metal tubes and transformed into the metal-barreled hand cannon, and the technology gradually spread throughout Eurasia during the 14th century, but there is little information regarding how this spread occurred. Older firearms typically used black powder as a propellant. Beginning in the 1860s, black powder was gradually replaced by smokeless powder, which is mostly based on nitrocellulose. In contrast to black powder, it produces almost entirely gas upon combustion, earning it the title "smokeless powder." Most modern firearms (with the notable exception of smoothbore shotguns) have rifled barrels to impart a stabilizing spin to the bullet for improved external ballistics. Modern firearms can be described by their caliber (i.e. bore diameter). For handguns and rifles this is given in millimeters or inches (e.g. 7.62mm or .308 in.); in the case of shotguns, gauge or bore (e.g. 12 ga. or .410 bore.). They are also described by the type of action employed (single-shot vs. repeating, e.g. muzzleloader, breechloader, lever, bolt, pump, revolver, semi-automatic, fully automatic, etc.), together with the usual means of deportment (i.e. handheld or mounted). Further classification may make reference to the type of barrel bore used (i.e. rifled vs smoothbore) and to the barrel length (e.g. 24 inches), to the firing mechanism (e.g. matchlock, flintlock, wheellock, caplock or primer-ignited such as needlefire, pinfire, teat-fire, rimfire and centerfire, as well as the atypical electronic firing), to the design's primary intended use (e.g. hunting rifle, service rifle), or to the commonly accepted name for a particular variation (e.g. Gatling gun). Shooters aim firearms at their targets with hand-eye coordination, using either iron sights or optical sights such as scope, red dot or holographic sights. The effective range of handguns and shotguns generally does not exceed 100 metres (110 yd; 330 ft), while most rifles are accurate to 500 metres (550 yd; 1,600 ft) using iron sights, or to longer ranges whilst using optical sights. Purpose-built sniper rifles and anti-materiel rifles are accurate to ranges of more than 2,000 metres (2,200 yd). Firearm rounds may be dangerous or lethal well beyond their accurate range; the minimum distance for safety is much greater than the specified range for accuracy.
Types
A firearm is a barreled weapon that inflicts damage on targets by launching one or more projectiles driven by rapidly expanding high-pressure gas produced by exothermic combustion (deflagration) of a chemical propellant, historically black powder, now smokeless powder. In the military, firearms are categorized into heavy and light weapons by their portability. Light firearms are those that can be readily carried by individual foot soldier, though they might require more than one individual (i.e. crew-served) to achieve optimal operational capacity. Heavy firearms are those that are too large and heavy to be transported on foot, or too unstable against recoil, and thus require the support of a weapons platform (e.g. a fixed mount, wheeled carriage, vehicle, aircraft or water vessel) to be tactically mobile or useful. The subset of light firearms that only use kinetic projectiles and are compact enough to be operated to full capacity by a single infantryman (individual-served) are also referred to as small arms. Such firearms include handguns such as pistols, revolvers, and derringers; and long guns such as rifles (and their subtypes), shotguns, submachine guns, and light machine guns. Among the world's arms manufacturers, the latest data from 2023 released by the Bureau of Alcohol, Tobacco, Firearms, and Explosives shows the top 30 firearms manufacturers in the United States are (in order of number of firearms manufactured): Ruger, SIG Sauer, Smith & Wesson, Savage Arms, Palmetto State Armory, Henry, Mossberg, Glock, Anderson Manufacturing (acquired by Ruger in 2025), Springfield Armory, Aero Precision, Heritage Manufacturing (owned by Taurus), Colt, KelTec, Kimber, FN, Beretta, Remington, Diamondback Firearms, Radical Firearms, Legacy Sports International, SCCY Firearms, Taurus, North American Arms, American Tactical, Shadow Systems, Browning, Daniel Defense, Wilson Combat, and Staccato 2011. Some of the world's largest firearm manufacturers outside the United States include Glock (Austria), Heckler & Koch (Germany), SIG Sauer (Germany/Switzerland), CZ (Czech Republic), Beretta (Italy), FN (Belgium), Taurus (Brazil), Norinco (China), Steyr Arms (Austria), Kalashnikov (Russia), Tokarev (Russia), and Miroku (Japan). As of 2018 the Small Arms Survey reported that there were over one billion firearms distributed globally, of which 857 million (about 85 percent) were in civilian hands. U.S. civilians alone account for 393 million (about 46 percent) of the worldwide total of civilian-held firearms, as of 2026 the number of civilian-held firearms is estimated to be as much as 500 million. This amounts to "120.5 firearms for every 100 residents", which increased to 150 guns per 100 residents by 2026. The world's armed forces control about 133 million (about 13 percent) of the global total of small arms, of which over 43 percent belong to two countries: the Russian Federation (30.3 million) and China (27.5 million). Law enforcement agencies control about 23 million (about 2 percent) of the global total of small arms.
Handguns
A handgun is, as defined generally and in many gun laws, a firearm that can be used with a single hand. They are the smallest of all firearms, and are common as sidearms, concealed carry weapons, or as backup weapons for self-defense. Handguns can be categorized into two broad types: pistols, which have a single fixed firing chamber machined into the rear of the barrel, and are often loaded using magazines of varying capacities; revolvers, which have a number of firing chambers or "charge holes" in a revolving cylinder, each one loaded with a single cartridge or charge; and derringers, broadly defined as any handgun that is not a traditional pistol nor a revolver, typically they are a small, pocket-sized pistol designed for easy concealment, featuring one or two barrels without a repeating mechanism being loaded either via the muzzle or breech. There are various types of the aforementioned handguns designed for different mechanisms or purposes, such as single-shot, manual repeating, semi-automatic, or automatic pistols; single-action, double-action, or double-action/single-action revolvers; and small, compact handguns for concealed carry such as pocket pistols and "Saturday night specials". Examples of pistols include Glocks, Browning Hi-Power, M1911 pistol, Makarov pistol, Walther PP, Luger pistol, Mauser C96, and Beretta 92. Examples of revolvers include the Colt Single Action Army, Smith & Wesson Model 10, Colt Official Police, Colt Python, New Nambu M60, and Mateba Autorevolver. Examples of derringers include the Remington Model 95, FP-45 Liberator, and COP .357 Derringer.
Long guns
A long gun is any firearm with a notably long barrel, typically a length of 10 to 30 inches (250 to 760 mm) (there are restrictions on minimum barrel length in many jurisdictions; maximum barrel length is usually a matter of practicality). Unlike a handgun, long guns are designed to be held and fired with both hands, while braced against the shoulder for better stability. The receiver and trigger group is mounted into a stock made of wood, plastic, metal, or composite material, which has sections that form a foregrip, rear grip, and optionally (but typically) a shoulder mount called the butt. Early long arms, from the Renaissance up to the mid-19th century, were generally smoothbore firearms that fired one or more ball shot, called muskets or arquebuses depending on caliber and firing mechanism. Since the 19th and 20th centuries, various types of long guns have been created for different purposes.
Rifles
A rifle is a long gun that has riflings (spiral grooves) machined into the bore (inner) surface of its barrel, imparting a gyroscopically stabilizing spin to the bullets that it fires. A descendant of the musket, rifles produce a single point of impact with each firing with a long range and high accuracy. For this reason, as well as for their ubiquity, rifles are very popular among militaries as service rifles, police as accurate long-range alternatives to their traditional shotgun long guns, and civilians for hunting, shooting sports, and self-defense. Many types of rifles exist owing to their wide adoption and versatility, ranging from mere barrel length differences as in short-barreled rifles and carbines, to classifications per the rifle's function and purpose as in semi-automatic rifles, automatic rifles and sniper rifles, to differences in the rifle's action as in falling block, rolling block, single-shot, break-action, bolt-action, and lever-action rifles. Examples of rifles of various types include the Henry rifle, Winchester Model 94, Winchester Model 70, Lee–Enfield, Gewehr 98, M1 Garand, AK-type, AR-15, Ruger 10/22, Ruger M77, Ruger Mini-14, Heckler & Koch G3, Remington Model 700, Remington Model 7600, and Heckler & Koch HK417.
Shotguns
A shotgun is a long gun that has a predominantly smoothbore barrel—meaning it lacks rifling—designed to fire a number of shot pellets in each discharge. These shot pellet sizes commonly range between 2 mm #9 birdshot and 8.4 mm #00 (double-aught) buckshot, and produce a cluster of impact points with considerably less range and accuracy compared to a rifle, since shot spreads during flight. Shotguns are also capable of firing single solid projectiles called slugs (typically used for hunting large animals), or specialty (often "less lethal") munitions such as bean bags or tear gas to function as a riot gun, or breaching rounds to function as a door breaching shotgun. Shotgun munitions, regardless of type, are packed into shotgun shells (cartridges designed specifically for shotguns) that are loaded into the shotgun for use; these shells are commonly loose and manually loaded one-by-one, though some shotguns accept magazines. Shotguns share many qualities with rifles, such as both being descendants of early long guns such as the musket; both having single-shot, break-action, bolt-action, lever-action, pump-action, semi-automatic, and automatic variants; and both being popular with military, police, and civilians for largely the same reasons. However, unlike rifles, shotguns are less favored in combat roles due to their low accuracy and limited effectiveness in modern warfare, with combat shotguns often only used for breaching, or close-quarters combat situations like jungle warfare, trench warfare, or clearing buildings during urban warfare; for versatility underbarrel attachments such as the M26 Modular Accessory Shotgun System are popular in the military, as they allow a soldier to wield a shotgun and an assault rifle simultaneously. Shotguns are still popular with civilians for the suitability of their shot spread in hunting, clay pigeon shooting, and home defense. Double-barreled shotguns are break-action shotguns with two parallel barrels (horizontal side-by-side or vertical over-and-under), allowing two single shots that can be loaded and fired in quick succession. Examples of shotguns include the Winchester Model 1897, Winchester SXP, Browning Auto-5, Ithaca 37, Remington Model 870, Mossberg 500, Benelli M4, Franchi SPAS-12, Atchisson AA-12.
Carbines
The traditional definition of a carbine was a shortened version of an existing rifle, the term is derived from the French word for rifleman, “carabinier”. A carbine was originally defined as a rifle with a barrel under 22 inches (56 cm), which was shorter than the common military rifle barrel lengths of 23 in (58 cm) to 26 in (66 cm) from the late 18th-early 20th centuries. One of the first carbines to be used by the United States Army was the Spencer carbine adopted in 1860, it had a 22 inch barrel and was designed to be more quickly drawn from a saddle scabbard. During the late 19th and early 20th century, U.S. Army Cavalry carried carbine conversions of lever action rifles like the Winchester Model 1873 Carbine, which had the standard 26 in (66 cm) barrel shortened to 20 in (51 cm). The definition of a carbine evolved and changed somewhat in the 20th century, especially in the United States after the passage of the National Firearms Act (NFA) in 1934. The NFA created the term short-barreled rifle (SBR), which is defined as a rifle with a barrel length under 16 in (41 cm) or with an overall length under 26 in (66 cm), under the NFA possession of an SBR is a class D felony unless the ATF issues a type of permit known as a NFA tax stamp. This led the international firearms industry (for the most part) to adopt the definition of a carbine as being any rifle with a barrel length under 20 in (51 cm), and in the U.S. carbine has come to mean any rifle with a barrel length between 20-16 inches, and while rifles with barrels under 16 inches are still defined as a carbine, they're usually called an SBR for clarification. Not all carbines are shortened versions of existing rifles, for example the M1 carbine was designed with a 17.75 in (45.1 cm) barrel and Ruger Mini-14 models have either 18.5 in (47 cm) or 16.1 in (41 cm) barrels. Carbines are regardless very similar to rifles and often have the same actions (single-shot, lever-action, bolt-action, semi-automatic, automatic, etc.). The small size of a carbine provides lighter weight and better maneuverability, making them ideal for close-quarters combat and storage in compact areas. This makes them popular firearms among special forces and police tactical units alongside submachine guns, considerably so since the late 1990s due to the familiarity and better stopping power of carbines compared to submachine guns. They are also popular with (and were originally mostly intended for) military personnel in roles that are expected to engage in combat, but where a full-size rifle would be an impediment to the primary duties of that soldier (logistical personnel, airborne forces, military engineers, officers, etc.), though since the turn of the millennium these have been superseded to a degree in some roles by personal defense weapons. Carbines are also common among civilian firearm owners who have size, space, and power concerns similar to military and police users. Examples of carbines include the Winchester Model 1892, Rifle No. 5 Mk I, SKS, M1 carbine, Ruger Mini-14, M4 carbine, Colt AR-15, and Kel-Tec SUB-2000.
Assault rifles
An assault rifle is commonly defined as a selective-fire rifle chambered in an intermediate cartridge (such as 5.56×45mm NATO, 7.62×39mm, 5.45×39mm, and .300 AAC Blackout) and fed with a detachable magazine. Assault rifles are also usually smaller than full-sized rifles such as battle rifles. Originating with the StG 44 produced by Nazi Germany during World War II, assault rifles have since become extremely popular among militaries and other armed groups due to their universal versatility, and they have made up the vast majority of standard-issue military service rifles since the mid-20th century. Various configurations of assault rifle exist, such as the bullpup, in which the firing grip is located in front of the breech instead of behind it. Examples of assault rifles include Kalashnikov rifle(such as the AK-47, AKM, and AK-74), the American M16 rifle and its M4 carbine variant, the Austrian Steyr AUG, the Belgian FN FAL and FNC, and the German Heckler & Koch G36.
Battle rifles
A battle rifle is commonly defined as a semi-automatic or selective-fire rifle that is larger or longer than an assault rifle and is chambered in a "full-power" cartridge (e.g. 7.62×51mm NATO, 7.92×57mm Mauser, 7.62×54mmR, 6.8x51mm). The term originated as a retronym to differentiate older full-powered rifles of these configurations like the M1 Garand and M14, from newer assault rifles using intermediate cartridges like the Heckler & Koch HK33 and M16, but it is sometimes used to describe similar modern rifles such as the FN SCAR. Battle rifles serve similar purposes as assault rifles, as they both are usually employed by ground infantry for essentially the same purposes. However, some prefer battle rifles for their more powerful cartridge, despite the added recoil. Some designated marksman rifles are configured from battle rifles, such as the Mk 14 Enhanced Battle Rifle and United States Marine Corps Designated Marksman Rifle, both essentially heavily modified and modernized variants of the M14 rifle. Examples of rifles considered to be battle rifles include the M1 Garand, M14, AR-10, FG 42, Gewehr 43, FN FAL, FN SCAR, SIG MCX Spear, Howa Type 64, and AK-308.
Sniper rifles
A sniper rifle is, per widespread definition, a high-powered precision rifle, often bolt-action or semi-automatic, with an effective range beyond that of a standard rifle, typically beyond 300 metres (330 yd). Though any rifle in a sniper configuration (usually with a telescopic sight and bipod) can be considered a sniper rifle, most sniper rifles are purpose-built for their applications, or are variants of existing rifles that have been modified to function as sniper rifles, such as the M1903A1/Unertl, which was the United States Marine Corps sniper rifle configuration of the M1903 Springfield; or the Type 97 sniper rifle used by the Imperial Japanese Army, which was essentially a standard Type 38 rifle that was modified to be lighter and come with a telescopic sight. Related developments are anti-materiel rifles, large-caliber rifles typically between 12.7 mm (0.50 in) to 14.5 mm (0.57 in) (sometimes larger)-i.e. .50 BMG (12.7x99mm NATO), 12.7 × 108 mm, 20x102mm-in calibers designed to destroy enemy materiel such as vehicles, supplies, or hardware; anti-material rifles are also used as extreme long-range sniper rifles for distances of 1,000 metres (1,100 yd) to 2,000 m (2,200 yd). Anti-tank rifles are anti-materiel rifles that were designed specifically to combat early armored fighting vehicles, but are now largely obsolete due to advances in vehicle armour. Scout sniper rifles are a broad class of rifles generally summed up as short, lightweight, portable sniper rifles used by Scout Snipers. A designated marksman rifle is a semi-automatic high-precision rifle, they're usually chambered in intermediate or full-power cartridges like the 7.62x51mm NATO, and are designed to fill the range gap between sniper rifles and regular infantry rifles, they are designed for engagements beyond 300 yards (270 m) with a maximum range of 800 yards (730 m), and are wielded by designated marksmen. Examples of sniper and scout rifles include the M40 rifle, Heckler & Koch PSG1, Walther WA 2000, Accuracy International AWM, M24 Sniper Weapon System, Mk 22 MOD 0 Advanced Sniper Rifle, Steyr Scout, Sako TRG, and CheyTac Intervention. Examples of anti-materiel and anti-tank rifles include the Mauser Tankgewehr M1918, Boys anti-tank rifle, Lahti L-39, PTRS-41, Barrett M82, Gepárd anti-materiel rifle, McMillan TAC-50, and Anzio 20mm rifle. Examples of designated marksman rifles include the SVD, SR-25, Dragunov SVU, Marine Scout Sniper Rifle, Mk 14 Enhanced Battle Rifle, M110 Semi-Automatic Sniper System, and M110A1 Compact Semi-Automatic Sniper System.
Automatic rifles
An automatic rifle is a magazine-fed rifle that is capable of automatic fire, including both burst fire rifles like the M16A4 & M4 which fire 3-round bursts with each trigger pull, and full auto rifles like the M16 & M4A1 which fire as long as the trigger is held down. They include most assault rifles and battle rifles, but originated as their own category of rifles capable of automatic fire, as opposed to the bolt-action and semi-automatic rifles commonly issued to infantry at the time of their invention in the early 20th century. They usually have smaller magazine capacities than machine guns; the French Chauchat had a 20-round box magazine and the U.S. M16 has a 30-round detachable magazine, while the Hotchkiss Mle 1914 machine gun, the French Army's standard machine gun at the time, was fed by a 250-round ammunition belt. Though automatic rifles are sometimes considered to be their own category, they are also occasionally considered to be other types of firearms that postdated their invention, usually as light machine guns. Automatic rifles are sometimes confused with machine guns or vice versa, or are defined as such by law; the National Firearms Act (NFA) and Title II of the Gun Control Act of 1968 (GCA) define a "machine gun" in 26 United States Code § 5845(b) as "... any firearm which shoots ... automatically more than one shot, without manual reloading, by a single function of the trigger". "Machine gun" is therefore largely synonymous with "automatic weapon" in American civilian parlance, covering all automatic firearms. In most jurisdictions, automatic rifles, as well as automatic firearms in general, are prohibited from civilian purchase or are at least heavily restricted. In the U.S. for instance, most automatic rifles are Title II weapons under the NFA & GCA that are heavily regulated and require prior approval from the ATF, a special permit, and payment of a $200 tax; in addition the Hughes Act of 1986, codified at 18 U.S.C. § 922(o), banned the transfer and possession of machine guns to civilians with the exception of machine guns registered prior to July 1, 1986, which is why civilian-legal machine guns in the U.S. are incredibly expensive. Examples of automatic rifles include the Cei-Rigotti, Lewis gun, Fedorov Avtomat, M1918 Browning automatic rifle, AK-47, M16, M4 carbine, and H&K 416.
Submachine guns
A submachine gun is a magazine-fed carbine chambered in a small-caliber handgun cartridge (such as 9×19mm Parabellum, .45 ACP, .22 Long Rifle, and .40 S&W). They cannot be considered machine guns due to their small-caliber, hence the prefix "sub-" to differentiate them from proper machine guns. Submachine guns are commonly associated with high rates of fire, automatic fire capabilities, and low recoil, though many submachine guns differentiate from this in various ways, such as having fairly low rates of fire or including burst and semi-automatic modes available through selective fire. Most submachine guns are the size of carbines and short-barreled rifles, and use similar configurations. Many are designed to take as little space as possible for use in close-quarters or for easy storage in vehicles and cases. Some submachine guns are designed and configured similar to pistols even down to size, and are thus occasionally classed as machine pistols, even if they are not actually a handgun (i.e. designed to require two hands to use). Submachine guns are considered ideal for close-quarters combat and are cheap to mass-produce. They were very common in military service through much of the 20th century, but have since been superseded in most combat roles by rifles, carbines, and personal defense weapons due to their low effective range and poor penetration against most body armor developed since the late 20th century. However, they remain popular among special forces and police for their effectiveness in close-quarters and low likelihood to overpenetrate targets. Examples of submachine guns include the MP 18, MP 40, Thompson submachine gun, M3 submachine gun, Uzi, Heckler & Koch MP5, Spectre M4, Steyr TMP, Heckler & Koch UMP, PP-2000, KRISS Vector, and SIG MPX.
Personal defense weapons
A personal defense weapon (PDW) is a light-weight, short, collapsible, folding rifle or submachine gun, chambered in either intermediate or rifle rounds, designed specifically for close-quarters protection. A PDW is more compact than a rifle, but is more effective than a handgun at intermediate ranges around 100 yards (91 m) to 200 yd (180 m), and are capable of holding more ammunition than a handgun. Examples of automatic PDWs used by military and law enforcement are the FN P90 chambered in the 5.7×28mm intermediate cartridge, and the Heckler & Koch MP7 chambered for the HK 4.6×30mm armor-piercing cartridge. An example of a semi-automatic civilian-legal PDW would be an AR pistol, which are essentially short-barreled AR-15s with an overall length under 26 in (66 cm) that use an arm brace instead of a buttstock, allowing it to be fired one-handed like a handgun; AR pistols can be chambered in pistol cartridges like 9x19mm, .357 SIG, & .40 S&W, or rifle cartridges like the 5.56x45mm & .300 Blackout. Personal defense weapons were developed to provide rear and "second-line" personnel not otherwise armed with high-caliber firearms (vehicle and weapon crews, engineers, logistical personnel, etc.) with a method of effective self-defense against skirmishers and infiltrators who cannot effectively be defeated by low-powered submachine guns and handguns, often the only firearms suitable for those personnel (while they could be issued rifles or carbines, those would become unnecessary burdens in their normal duties, during which the likelihood of hostility is fairly rare regardless, making their issuance questionable). PDWs were also designed for use by special forces teams as some use specialized ammunition designed to offer better penetration against modern body armor than traditional pistol rounds but with reduced recoil, such as the MP7, they also offer an advantage for missions when stealth and concealability are needed. PDWs are also used by law enforcement for situations when they don't want to appear conspicuously armed, such as undercover DEA and FBI agents or Secret Service agents on protection details, as a PDW can easily be concealed under a coat or jacket but still be rapidly deployed. Examples of personal defense weapons include the FN P90, Heckler & Koch MP7, AAC Honey Badger, ST Kinetics CPW, SIG MCX, and SIG MPX.
Machine guns
A machine gun is a fully-automatic firearm, chambered in intermediate or full-power rifle cartridges, designed to provide sustained automatic direct fire as opposed to the semi-automatic or burst fire of standard rifles. They are commonly associated with being belt-fed, though many machine guns are also fed by box, drum, pan, or hopper magazines. They generally have a high rate of fire and a large ammunition capacity, and are often used for suppressive fire to support infantry advances or defend positions from enemy assaults. Owing to their versatility and firepower, they are also commonly installed on military vehicles and military aircraft, either as main or ancillary weapons. Many machine guns are individual-served and can be operated by a single soldier, though some are crew-served weapons that require a dedicated crew of soldiers to operate, usually between two and six soldiers depending on the machine gun's operation and the crew members' roles (ammunition bearers, spotters, etc.). Machine guns can be divided into three categories: light machine guns, individual-served machine guns of an intermediate cartridge that are usually magazine-fed; medium machine guns, belt-fed machine guns of a full-power caliber and a certain weight that can be operated by an individual but tend to work best with a crew; and heavy machine guns, machine guns that are too large and heavy to be carried and are thus mounted to something (like a tripod or military vehicle), and require a crew to operate. A general-purpose machine gun combines these categories under a single flexible machine gun platform, often one that is most suitable as a light or medium machine gun but fares well as a heavy machine gun. A closely related concept is the squad automatic weapon, a portable light machine gun or even a modified rifle that is designed and fielded to provide a squad with rapid direct fire. Examples of machine guns include the Maxim gun, M2 Browning, Bren light machine gun, MG 42, PK machine gun, FN MAG, M249 light machine gun, RPK, IWI Negev, and M134 Minigun.
Action
Types aside, firearms are also categorized by their "action", which describes their loading, firing, and unloading cycle.
=== Manual === Manual action or manual operation is essentially any type of firearm action that is loaded, and usually also fired, one cartridge at a time by the user, rather than automatically. Manual action firearms can be divided into two basic categories: single-shot firearms that can only be fired once per barrel before it must be reloaded or charged via an external mechanism or series of steps; and repeating firearms that can be fired multiple times per barrel, but can only be fired once with each subsequent pull of the trigger or ignite, and the firearm's action must be reloaded or charged via an internal mechanism between trigger pulls. Types of manual actions include lever action, bolt action, and pump action.
==== Break action ==== Break action or hinge action firearms open like a door on a hinge, providing access to the breech to load or unload the firearm, once the gun has been fired the action can then be opened to unload the spent shell(s) and reload. This type of action is most common with shotguns, but it is also seen with certain types of rifles such as double rifles and certain types of pistols. Break-action firearms commonly use either a single barrel, meaning only one shot can be fired before reloading, or use two barrels like with double-barreled or over-under shotgun and rifles. Examples of break-action single barrel shotguns include the Winchester Model 37, a double-barrel example is the Stoeger Coach Gun, and a break-action rifle example would be the high end Holland & Holland double rifle, such as the .500 Nitro Express.
Lever action
Lever action is a repeating action that is operated by using a cocking handle (the "lever") located around the trigger guard area (often incorporating it) that is pulled down then back up to move the bolt via internal linkages. As the bolt moves back it pushes the hammer back (most lever-action firearms use a hammer) into the cocked position, or in the case of a hammerless model it resets the firing pin mechanism. This also causes the bolt to expel the old cartridge and a fresh round to pop out of the magazine tube or box (most lever-action rifles use a tubular magazine), with the follower raising the round up into position, then as the lever is pushed back up the bolt closes and pushes the fresh round into the chamber. Most lever-action firearms are rifles, but there are a few types of lever-action shotguns. Examples of lever-action rifles include the Henry rifle, Winchester Model 1894, & Marlin Model 1895.
Revolving action
Revolving action is a type of firearm action primarily found on handguns known as revolvers, but there are a few types of revolving rifles and shotguns. Revolvers are so named because cartridges are loaded into a cylinder, the cylinder has separate chambers for each cartridge (the most common size is six), as the revolver is fired the cylinder rotates (or "revolves") aligning each of the chambers with the barrel. There are two types of revolvers: single-action and double-action. With single-action revolvers, the hammer must be manually cocked back by the operator each time the gun is fired to rotate the cylinder. With double-action revolvers, pulling the trigger rotates the cylinder, cocks the hammer back, and releases the hammer all in one motion, allowing for a faster rate-of-fire; however the revolver can also be fired single-action style by manually cocking the hammer, this makes the trigger pull much lighter and improves accuracy. Some modern revolvers are known as double-action only, instead of having an external hammer they use an internal striker mechanism, as the trigger is pulled it rotates the cylinder and resets the striker's firing pin, as such it can only be fired double-action style. Examples of revolvers include the Colt Single Action Army, Colt M1889 (early double-action), Colt Python (modern double-action), Ruger Single-Six (modern single-action), & Ruger LCR (double-action only).
Bolt action
Bolt action is a repeating (and rarely single-shot) action that is operated by directly manipulating the bolt via a bolt handle. The bolt is unlocked from the receiver, then pulled back to open the breech, ejecting a cartridge, and cocking the striker and engaging it against the sear; when the bolt is returned to the forward position, a new cartridge, if loaded, is pushed out of the magazine and into the barrel chamber, and the breech is re-locked. Most bolt-action firearms are rifles, but a few are shotguns. Two designs of bolt action exist: rotating bolt, where the bolt must be axially rotated to unlock and lock the receiver; and straight pull, which does not require the bolt to be rotated, simplifying the bolt action mechanism and allowing for a greater rate of fire. Examples of bolt-action rifles include the Winchester Model 70, Remington Model 700, Ruger M77, & Savage Model 110.
Pump action
Pump action or slide action is a repeating action that is operated by moving a sliding handguard (the "pump") on the gun's forestock rearward (frontward on some models), ejecting any spent cartridges and cocking the hammer or striker, then moving the handguard forward to load a new cartridge into the chamber. It is most common on shotguns, though pump action rifles and grenade launchers also exist. Examples of pump-action firearms include the Remington Model 870, Mossberg 500, & Winchester Model 1200 shotguns and Remington Model 7600 rifle.
=== Automatic === Automatic, autoloading or self-loading firearms use the energy, force, and/or gases generated by the cartridge being discharged to cycle the action. There are three primary methods of operation for automatic firearms: blowback, gas-operated, and recoil-operated. Blowback firearms use the energy from the motion of the cartridge case as it is pushed to the rear by expanding gas created by the ignition of the gunpowder in the cartridge. Gas-operated firearms use a portion of high-pressure gas from the cartridge being fired to cycle the action, there are two main types of gas-operated firearms: direct impingement in which the gas is captured by a gas block then directed back into the action forcing the bolt backwards into a spring, piston operated guns use the gas in the gas block to force a piston above the barrel backwards to cycle the bolt. Recoil-operated firearms use the force of the recoil to cycle the action, in recoil-operated firearms the barrel is free-floating and locked together with the slide, the barrel & slide are then moved backwards by the recoil, ejecting the spent case and loading a fresh one from the magazine, with a spring propelling them back into the forward position. An example of a blowback firearm is the Walther PPK. Examples of gas-operated guns are the M16 & AR-15 (direct impingement) and AK-47 (piston operated). An example of a recoil operated firearm is a Glock pistol.