Editing Firearm (section)

== Types ==
{{for|a more detailed list of common firearms|List of firearms|List of most-produced firearms|Small arms and light weapons}}
A firearm is a [[Gun barrel|barreled]] weapon that inflicts damage on targets by launching one or more [[projectile]]s driven by rapidly expanding high-pressure gas produced by [[Exothermic reaction|exothermic]] combustion ([[deflagration]]) of a chemical [[propellant]], historically [[black powder]], now [[smokeless powder]].<ref name="Cole"/><ref name="Merriam-webster.com"/><ref name="Firearm"/>

In the military, firearms are categorized into ''heavy'' and ''light'' weapons regarding their portability by [[infantry]].  Light firearms are those that can be readily carried by individual [[foot soldier]], though they might still require more than one individual ([[Crew-served weapon|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 [[Weapon mount#Static mount|fixed mount]], [[Gun carriage|wheeled carriage]], [[vehicle]], [[aircraft]] or [[water vessel]]) to be tactically [[Mobility (military)|mobile]] or useful.

The [[subset]] of light firearms that only use [[projectile#Kinetic projectiles|kinetic projectile]]s 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 [[handgun]]s such as [[pistol]]s, [[revolver]]s, and [[derringer]]s; and [[long gun]]s such as [[rifle]]s (and their subtypes), [[shotgun]]s, [[submachine gun]]s, and [[machine gun]]s.<ref>{{Cite web|url= https://www.britannica.com/technology/small-arm/|title= Small arm|last1= Weller|first1= Jac|last2= Guilmartin|first2= John|date= November 7, 2017|website= Britannica|publisher= Encyclopædia Britannica, inc.|access-date= February 23, 2019|last3= Ezell|first3= Edward|archive-date= May 12, 2021|archive-url= https://web.archive.org/web/20210512222707/https://www.britannica.com/technology/small-arm|url-status= live}}</ref>

Among the world's [[List of modern armament manufacturers|arms manufacturer]]s, the top firearms manufacturers are [[Browning Arms|Browning]], [[Remington Arms|Remington]], [[Colt Defense|Colt]], [[Sturm, Ruger & Co.|Ruger]], [[Smith & Wesson]], [[Savage Arms|Savage]], [[O.F. Mossberg & Sons|Mossberg]] (United States), [[Heckler & Koch]], [[SIG Sauer]], [[Carl Walther GmbH|Walther]] (Germany), [[Česká zbrojovka Uherský Brod|ČZUB]] (Czech Republic), [[Glock Ges.m.b.H.|Glock]], [[Steyr Arms]] (Austria), [[FN Herstal]] (Belgium), [[Beretta]] (Italy), [[Norinco]] (China), [[Rostec]], and [[Kalashnikov Concern|Kalashnikov]] (Russia). Former top producers included the [[Springfield Armory]] (United States), the [[Royal Small Arms Factory]] (United Kingdom), [[Mauser]] (Germany), [[Steyr-Daimler-Puch]] (Austria), and Rock Island Armory under [[Armscor (Philippines)|Armscor]] (Philippines).{{citation needed|date=July 2020}}

{{As of|2018}} the [[Small Arms Survey]] reported that there were over one billion firearms distributed globally, of which 857&nbsp;million (about 85 percent) were in [[civilian]] hands.<ref name="smallarmssurvey.org">{{cite web |title= Small Arms Survey reveals: More than one billion firearms in the world |url= http://www.smallarmssurvey.org/de/about-us/highlights/2018/highlight-bp-firearms-holdings.html |archive-url= https://web.archive.org/web/20180619120414/http://www.smallarmssurvey.org/de/about-us/highlights/2018/highlight-bp-firearms-holdings.html |url-status= dead |archive-date= June 19, 2018 |website= Small Arms Survey |access-date= 15 January 2019 |date= 2018}}</ref><ref name="ReferenceA">{{cite report |author= Aaron Karp| date= June 2018 |title= Estimating Global Civilian-Held Firearms Numbers |url= http://www.smallarmssurvey.org/fileadmin/docs/T-Briefing-Papers/SAS-BP-Civilian-Firearms-Numbers.pdf |archive-url= https://web.archive.org/web/20180620231909/http://www.smallarmssurvey.org/fileadmin/docs/T-Briefing-Papers/SAS-BP-Civilian-Firearms-Numbers.pdf |url-status= dead |archive-date= June 20, 2018 |publisher= Small Arms Survey}}</ref> U.S. civilians alone account for 393&nbsp;million (about 46 percent) of the worldwide total of civilian-held firearms.<ref name="ReferenceA"/> This amounts to "120.5 firearms for every 100 residents".<ref name="ReferenceA"/> The world's [[armed forces]] control about 133&nbsp;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&nbsp;million) and [[China]] (27.5&nbsp;million).<ref name="smallarmssurvey.org"/> [[Law enforcement agency|Law enforcement agencies]] control about 23&nbsp;million (about 2 percent) of the global total of small arms.<ref name="smallarmssurvey.org"/>

=== Handguns ===
{{main|Handgun}}
[[Image:Colt Autentica.jpg|thumb|The [[Colt Single Action Army]], a revolver chambered in [[.45 Colt]]]]
[[File:Glock 19 Gen 4 pistol.JPG|thumb|The [[Glock 19]], a pistol chambered in [[9×19mm Parabellum]]]]

A handgun is, as defined generally and in many [[gun laws]], a firearm that can be used with a single hand.<ref name="act60of2000" /><ref name="www5.austlii.edu.au">{{cite web |title=Firearms Act 1996 - Sect 3 Definitions |url=http://www5.austlii.edu.au/au/legis/vic/consol_act/fa1996102/s3.html |website=AustLII |url-status=live |archive-url=https://web.archive.org/web/20200612093619/http://www5.austlii.edu.au/au/legis/vic/consol_act/fa1996102/s3.html |archive-date=2020-06-12 |access-date=2020-03-07}}</ref><ref>{{Cite web |title=U.S.C. Title 18 - Crimes and Criminal Procedure {{!}} Part I - Crimes {{!}} Chapter 44 - Firearms {{!}} Sec. 921 - Definitions |website=GovInfo |url=https://www.govinfo.gov/content/pkg/USCODE-2018-title18/html/USCODE-2018-title18-partI-chap44-sec921.htm |url-status=live |archive-url=https://web.archive.org/web/20201024224614/https://www.govinfo.gov/content/pkg/USCODE-2018-title18/html/USCODE-2018-title18-partI-chap44-sec921.htm |archive-date=2020-10-24 |access-date=2020-09-24}}</ref><ref>{{Cite web |title=Firearms - Guides - Importation & Verification of Firearms - Gun Control Act Definition - Pistol |website=Bureau of Alcohol, Tobacco, Firearms and Explosives |url=https://www.atf.gov/firearms/firearms-guides-importation-verification-firearms-gun-control-act-definition-pistol |url-status=live |archive-url=https://web.archive.org/web/20200920014146/https://www.atf.gov/firearms/firearms-guides-importation-verification-firearms-gun-control-act-definition-pistol |archive-date=2020-09-20 |access-date=2020-09-24}}</ref> They are the smallest of all firearms, and are common as [[Sidearm (weapon)|sidearm]]s, [[concealed carry]] weapons, or as backup weapons for [[self-defense]].

Handguns can be categorized into two broad types: [[pistol]]s, which have a single fixed firing chamber machined into the rear of the barrel, and are often loaded using magazines of varying capacities; [[revolver]]s, which have a number of firing chambers or "charge holes" in a [[Cylinder (firearms)|revolving cylinder]], each one loaded with a single [[Cartridge (firearms)|cartridge]] or charge; and [[derringer]]s, broadly defined as any handgun that is not a traditional pistol nor a revolver.

There are various types of the aforementioned handguns designed for different mechanisms or purposes, such as [[single-shot]], [[Lever action|manual repeating]], [[Semi-automatic pistol|semi-automatic]], or [[Machine pistol|automatic]] pistols; [[single-action]], [[Trigger (firearms)#Double-action only|double-action]], or [[Trigger (firearms)#Double-action/single-action|double-action/single-action]] revolvers; and small, compact handguns for concealed carry such as [[pocket pistol]]s and "[[Saturday night special]]s".

Examples of pistols include [[Glock]]s, [[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 ===
{{main|Long gun}}

A long gun is any firearm with a notably long barrel, typically a length of {{convert|10|to|30|in|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 either the hip or 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 [[musket]]s or [[arquebus]]es depending on caliber and firing mechanism. Since the 19th and 20th centuries, various types of long guns have been created for different purposes.

==== Rifles ====
{{main|Rifle}}
[[File:Bastogne War Museum Mosin-Nagant Model 1944 27-02-2021 11-13-43.jpg|thumb|The [[Mosin–Nagant]], a rifle chambered in [[7.62×54mmR]]]]

A rifle is a long gun that has [[rifling]]s (spiral grooves) machined into the [[Gauge (firearms)|bore]] (inner) surface of its barrel, imparting a gyroscopically stabilizing spin to the [[bullet]]s 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 rifle]]s, 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 rifle]]s and [[carbine]]s, to classifications per the rifle's function and purpose as in [[semi-automatic rifle]]s, [[automatic rifle]]s and [[sniper rifle]]s, to differences in the rifle's action as in [[single-shot]], [[break-action]], [[bolt-action]], and [[lever-action]] rifles.

Examples of rifles of various types include the [[Henry rifle]], [[Winchester rifle]], [[Lee–Enfield]], [[Gewehr 98]], [[M1 Garand]], [[MAS-36 rifle]], [[AKM]], [[Ruger 10/22]], [[Heckler & Koch G3]], [[Remington Model 700]], and [[Heckler & Koch HK417]].

==== Shotguns ====
{{main|Shotgun}}
[[File:Mossberg 500a 1.jpg|thumb|The [[Mossberg 500]], a shotgun chambered in [[12-gauge]]]]

A shotgun is a long gun that has a predominantly [[smoothbore]] barrel—meaning it lacks rifling—designed to fire a number of [[Shot (pellet)|shot pellets]] in each discharge. These shot pellet sizes commonly range between 2&nbsp;mm #9 birdshot and 8.4&nbsp;mm #00 (double-aught) buckshot, and produce a cluster of impact points with considerably less range and accuracy, since [[Shotgun shell#Spread|shot spreads]] during flight. Shotguns are also capable of firing single solid projectiles called [[Shotgun slug|slugs]], or specialty (often "[[Non-lethal weapon|less lethal]]") munitions such as [[Bean bag round|bean bags]] or [[tear gas]] to function as a [[riot gun]] or [[breaching round]]s to function as a [[door breaching]] shotgun. Shotgun munitions, regardless of type, are packed into [[shotgun shell]]s (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 shotgun|semi-automatic]], and [[automatic shotgun|automatic]] variants; and both being popular with militaries, 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 shotgun]]s often only used for breaching or [[close-quarters combat]] and sometimes limited to underbarrel attachments such as the [[M26 Modular Accessory Shotgun System]]. Shotguns are still popular with civilians for the suitability of their shot spread in hunting, [[clay pigeon shooting]], and home defense.

[[Double-barreled shotgun]]s 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]], [[Browning Auto-5]], [[Ithaca 37]], [[Remington Model 870]], [[Mossberg 500]], [[Benelli M4]], [[Franchi SPAS-12]], [[Atchisson AA-12]], and [[Knight's Armament Company Masterkey]].

==== Carbines ====
{{main|Carbine}}
[[File:M1 Carbine Mk I - USA - Armémuseum noBG croped.jpg|thumb|The [[M1 carbine]], a uniquely-designed carbine, chambered in [[.30 carbine]]]]
[[File:Coltm4a1.jpeg|thumb|The [[M4 carbine]], a carbine derivative of the [[M16 rifle]], chambered in [[5.56×45mm NATO]]]]

A carbine is a long gun, usually a rifle, that has had its barrel shortened from its original length or is of a certain size smaller than standard rifles, but is still large enough to be considered a long gun. How considerable the difference is between a rifle and a carbine varies; for example, the standard [[Heckler & Koch G36]]'s barrel has a length of 480&nbsp;mm (18.9&nbsp;in), the G36K carbine variant's barrel is 318&nbsp;mm (12.5&nbsp;in), and the G36C compact variant's barrel is 228&nbsp;mm (9.0&nbsp;in). Some carbines are also redesigned compared to their rifle counterparts, such as the aforementioned G36/G36K and G36C, or the [[AK-74]] and [[AKS-74U]]. However, some carbines, such as the [[M1 carbine]], are not a variant of any existing design and are their own firearm model. Carbines are regardless very similar to rifles and often have the same actions (single-shot, lever-action, bolt-action, semi-automatic, automatic, etc.). This similarity has given carbines the alternate name of ''short barreled rifle'' (SBR), though this more accurately describes a full-size rifle with a shortened carbine-style barrel for close-quarters use.

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 unit]]s alongside [[submachine gun]]s, 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 ([[Military logistics|logistical]] personnel, [[airborne forces]], [[military engineers]], [[Officer (armed forces)|officers]], etc.), though since the turn of the millennium these have been superseded to a degree in some roles by [[personal defense weapon]]s. 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]], and [[Kel-Tec SUB-2000]].

==== Assault rifles ====
{{main|Assault rifle}}
[[File:Kalaschnikow AK 107 noBG.png|thumb|The [[AK-107]], an assault rifle chambered in [[5.45×39mm]]]]

An assault rifle is commonly defined as a [[selective fire|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 (firearms)|magazine]].<ref name="BritanicaDef">{{cite encyclopedia |title=Assault rifle |encyclopedia=Encyclopædia Britannica |url=https://www.britannica.com/EBchecked/topic/39165/assault-rifle |access-date=2023-06-20 |date=3 July 2010 |archive-url=https://web.archive.org/web/20121124070604/https://www.britannica.com/EBchecked/topic/39165/assault-rifle |archive-date=24 November 2012 |url-status=live}}</ref><ref name="autogenerated1">C. Taylor, ''The Fighting Rifle: A Complete Study of the Rifle in Combat'', {{ISBN|0-87947-308-8}}</ref><ref name="autogenerated2">F.A. Moyer ''Special Forces Foreign Weapons Handbook'', {{ISBN|0-87364-009-8}}</ref><ref name="autogenerated4">R.J. Scroggie, F.A. Moyer ''Special Forces Combat Firing Techniques'', {{ISBN|0-87364-010-1}}</ref><ref name="Musgave, Daniel D. 1967">Musgave, Daniel D., and Thomas B. Nelson, ''The World's Assault Rifles'', vol. II, The Goetz Company, Washington, D.C. (1967): 1</ref> Assault rifles are also usually smaller than full-sized rifles such as [[battle rifle]]s.

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 rifle]]s 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 [[Chamber (firearms)|breech]] instead of behind it.

Examples of assault rifles include the [[Kalashnikov rifle]]s of Soviet and Russian origin (such as the [[AK-47]], [[AKM]], and [[AK-74]]), as well as the American [[M4 carbine]] and [[M16 rifle]].

==== Battle rifles ====
{{main|Battle rifle}}
[[File:FN FAL compilation.jpg|thumb|The [[FN FAL]], a battle rifle chambered in [[7.62×51mm NATO]]]]

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]]). The term originated as a [[retronym]] to differentiate older full-powered rifles of these configurations like the [[M1 Garand]], from newer assault rifles using [[intermediate cartridge]]s like the [[Heckler & Koch HK33]], 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 [[FG 42]], [[Gewehr 43]], [[FN FAL]], [[Howa Type 64]], and [[Desert Tech MDR]].

==== Sniper rifles ====
{{main|Sniper rifle}}
[[File:G22 ohne Schalldaempfer.jpg|thumb|upright=1.2|The [[Accuracy International Arctic Warfare]], a sniper rifle chambered in [[7.62×51mm NATO]] and [[.308 Winchester]]]]
[[File:M107 1.jpg|thumb|The [[Barrett M82]], an anti-materiel rifle chambered in [[.50 BMG]]]]

A sniper rifle is, per widespread definition, a high-powered precision rifle, often [[bolt-action]] or semi-automatic, with an [[effective range]] farther than that of a standard rifle. 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 [[Type 97 sniper rifle]], 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 rifle]]s, large-caliber rifles designed to destroy enemy [[materiel]] such as vehicles, supplies, or hardware; [[anti-tank rifle]]s, anti-materiel rifles that were designed specifically to combat early [[armoured fighting vehicle]]s, but are now largely obsolete due to advances in [[vehicle armour]]; [[scout rifle]]s, a broad class of rifles generally summed up as short, lightweight, portable sniper rifles; and [[designated marksman rifle]]s, semi-automatic high-precision rifles, usually chambered in intermediate or full-power cartridges, that fill the range gap between sniper rifles and regular rifles and are designed for [[designated marksmen]] in squads.

Examples of sniper and scout rifles include the [[M40 rifle]], [[Heckler & Koch PSG1]], [[Walther WA 2000]], [[Accuracy International AWM]], [[M24 Sniper Weapon System]], [[Steyr Scout]], [[Sako TRG]], and [[CheyTac Intervention]]. Examples of anti-materiel and anti-tank rifles include the [[Mauser Tankgewehr M1918]], [[Boys anti-tank rifle]], [[PTRS-41]], [[Barrett M82]], [[Gepárd anti-materiel rifle]], and [[McMillan TAC-50]]. Examples of designated marksman rifles include the [[SVD (rifle)|SVD]], [[SR-25]], [[Dragunov SVU]], [[Marine Scout Sniper Rifle]], [[Mk 14 Enhanced Battle Rifle]], and [[M110 Semi-Automatic Sniper System]].

==== Automatic rifles ====
{{main|Automatic rifle}}
[[File:AVS-36 AM.068386 (2) (cropped).jpg|thumb|The [[AVS-36]], an automatic rifle chambered in [[7.62×54mmR]]]]

An automatic rifle is a magazine-fed rifle that is capable of automatic fire. 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. They usually have smaller magazine capacities than [[machine gun]]s; the French [[Chauchat]] had a 20-round box 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 gun]]s. Automatic rifles are sometimes confused with machine guns or vice versa, or are defined as such by law; the [[National Firearms Act]] and [[Firearm Owners Protection Act]] define a "machine gun" in [[United States Code]] ''Title 26, Subtitle E, Chapter 53, Subchapter B, Part 1, § 5845'' 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]] that require certain licenses and are greatly regulated.

Examples of automatic rifles include the [[Cei-Rigotti]], [[Lewis gun]], [[Fedorov Avtomat]], and [[M1918 Browning automatic rifle]].

==== Machine guns ====
{{main|Machine gun}}
[[File:M60 machine gun.jpg|thumb|The [[M60 machine gun|M60]], a general-purpose machine gun chambered in [[7.62×51mm NATO]]]]

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 vehicle]]s 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 weapon]]s 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 gun]]s, individual-served machine guns of an [[intermediate cartridge]] that are usually magazine-fed; [[medium machine gun]]s, 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 gun]]s, machine guns that are too large and heavy to be carried and are thus [[Weapon mount|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]].

==== Submachine guns ====
{{main|Submachine gun}}
[[File:Heckler & Koch MP5-1.jpg|thumb|The [[Heckler & Koch MP5]], a submachine gun chambered in [[9×19mm Parabellum]]]]

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 "[[wiktionary:sub-|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 pistol]]s, 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 [[Overpenetrating|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 ====
{{main|Personal defense weapon}}
[[File:BundeswehrMP7.JPG|thumb|The [[Heckler & Koch MP7]], a personal defense weapon chambered in [[HK 4.6×30mm]]]]

A personal defense weapon is, in simplest terms, a submachine gun that is designed to fire ammunition with ballistic performance that is similar to (but not actually a type of) rifle cartridges, often called "sub-intermediate" cartridges. In this way, it combines the high automatic rate of fire, reliable low recoil, and lightweight compact maneuverability of submachine guns with the versatility, penetration, and effective range of rifles, effectively making them an "in-between" of submachine guns and carbines.

Personal defense weapons were developed to provide [[Rear (military)|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 [[skirmisher]]s and [[Infiltration tactics|infiltrator]]s 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). Thus, per their name, personal defense weapons allow these personnel to effectively defend themselves from enemies and repel attacks themselves or at least until support can arrive. They are not intended for civilian self-defense due to their nature as automatic firearms (which are usually prohibited from civilian purchase), though some semi-automatic PDWs exist for the civilian market, albeit often with longer barrels.

Examples of personal defense weapons include the [[FN P90]], [[Heckler & Koch MP7]], [[AAC Honey Badger]], and [[ST Kinetics CPW]].