Editing Machine gun (section)

== Modern overview ==
{{more citations needed|1=section|date=July 2023}}
[[File:JGSDF Type73 Light Truck 20081025-2.JPG|thumb|left|A vehicle with a [[M2 Browning|Sumitomo M2 heavy machine gun]] mounted at the rear]]
Unlike [[semi-automatic firearm]]s, which require one trigger pull per round fired, a machine gun is designed to continue firing for as long as the trigger is held down.<ref>{{Cite web |title=Machine gun {{!}} History, Description, & Facts {{!}} Britannica |url=https://www.britannica.com/technology/machine-gun |access-date=2023-03-06 |website=www.britannica.com |language=en |archive-date=2020-10-01 |archive-url=https://web.archive.org/web/20201001220302/https://www.britannica.com/technology/machine-gun |url-status=live }}</ref>  Nowadays, the term is restricted to relatively heavy [[crew-served weapon]]s, able to provide continuous or frequent bursts of automatic fire for as long as ammunition feeding is replete. Machine guns are used against [[infantry]], low-flying [[aircraft]], small [[boat]]s and lightly/un[[vehicle armor|armored]] [[land vehicle]]s, and can provide [[suppressive fire]] (either [[direct fire|directly]] or [[indirect fire|indirectly]]) or enforce [[area denial]] over a sector of land with [[grazing fire]]. They are commonly mounted on fast attack vehicles such as [[Technical (vehicle)|technicals]] to provide heavy mobile firepower, armored vehicles such as [[tank]]s for engaging targets too small to justify the use of the primary weaponry or too fast to effectively engage with it, and on aircraft as defensive armament or for strafing ground targets, though on fighter aircraft true machine guns have mostly been supplanted by large-caliber rotary guns.

Some machine guns have in practice sustained fire almost continuously for hours; other automatic weapons overheat after less than a minute of use. Because they become very hot, the great majority of designs fire from an [[open bolt]], to permit air cooling from the [[Breech-loading weapon|breech]] between bursts. They also usually have either a barrel cooling system, slow-heating heavyweight barrel, or removable barrels which allow a hot barrel to be replaced.

Although subdivided into "[[Light machine gun|light]]", "[[Medium machine gun|medium]]", "[[Heavy machine gun|heavy]]" or "[[general-purpose machine gun|general-purpose]]", even the lightest machine guns tend to be substantially larger and heavier than standard infantry arms.<ref>{{Cite book|url=https://www.worldcat.org/oclc/441045309|title=Weapon : a visual history of arms and armour|date=2006|publisher=Dorling Kindersley|others=Richard Holmes|isbn=1-4053-1619-5|location=London|oclc=441045309}}</ref> Medium and heavy machine guns are either mounted on a [[tripod (weapon)|tripod]] or on a vehicle; when carried on foot, the machine gun and associated equipment (tripod, ammunition, spare barrels) require additional crew members.

Light machine guns are designed to provide mobile fire support to a squad and are typically air-cooled weapons fitted with a box magazine or drum and a bipod; they may use full-size rifle rounds, but modern examples often use intermediate rounds. Medium machine guns use full-sized rifle rounds and are designed to be used from fixed positions mounted on a tripod. The heavy machine gun is a term originating in World War I to describe heavyweight medium machine guns and persisted into World War II with Japanese [[Hotchkiss M1914 machine gun|Hotchkiss M1914]] clones; today, however, it is used to refer to automatic weapons with a caliber of at least {{cvt|12.7|mm|in|1}},<ref>{{cite web|url=http://www.marines.mil/Portals/59/MCWP%203-15.1.pdf|title=Machine Guns and Machine Gun Gunnery |publisher=US Marine Corps |access-date=23 December 2017|archive-url=https://web.archive.org/web/20180219042306/http://www.marines.mil/Portals/59/MCWP%203-15.1.pdf|archive-date=19 February 2018|url-status=live}}</ref> but less than {{cvt|20|mm|in|1}}. A general-purpose machine gun is usually a lightweight medium machine gun that can either be used with a bipod and drum in the light machine gun role or a tripod and belt feed in the medium machine gun role.

[[File: A soldier with the Ukrainian Land Forces fires a Degtyaryov-Shpagin Large-Caliber heavy machine gun.jpg|thumb|upright|[[DShK]] in the heavy role]]

Machine guns usually have simple iron sights, though the use of optics is becoming more common. A common aiming system for direct fire is to alternate solid ("ball") rounds and [[tracer ammunition]] rounds (usually one tracer round for every four ball rounds), so shooters can see the trajectory and "walk" the fire into the target, and direct the fire of other [[soldier]]s.

Many [[heavy machine gun]]s, such as the [[M2 Browning machine gun|Browning M2]] [[.50 BMG]] machine gun, are accurate enough to engage targets at great distances. During the [[Vietnam War]], [[Carlos Hathcock]] set the [[Longest recorded sniper kills|record for a long-distance shot]] at {{convert|7382|ft|abbr=on}} with a .50 caliber heavy machine gun he had equipped with a [[telescopic sight]].<ref name="henderson">Henderson, Charles (2005). ''Marine Sniper''. Berkley Caliber. {{ISBN|0-425-10355-2}}.</ref> This led to the introduction of .50 caliber [[anti-materiel rifle|anti-materiel sniper rifles]], such as the [[M82 Barrett rifle|Barrett M82]].

Other automatic weapons are subdivided into several categories based on the size of the bullet used, whether the [[Cartridge (firearms)|cartridge]] is fired from a [[closed bolt]] or an [[open bolt]], and whether the [[Action (firearms)|action]] used is locked or is some form of [[blowback (firearms)|blowback]].

Fully automatic firearms using pistol-caliber ammunition are called [[machine pistol]]s or submachine guns largely on the basis of size; those using shotgun cartridges are almost always referred to as [[automatic shotgun]]s. The term [[personal defense weapon]] (PDW) is sometimes applied to weapons firing dedicated armor-piercing rounds which would otherwise be regarded as machine pistols or SMGs, but it is not particularly strongly defined and has historically been used to describe a range of weapons from ordinary SMGs to compact assault rifles. [[Selective fire|Selective-fire]] rifles firing a full-power rifle cartridge from a closed bolt are called [[automatic rifle]]s or [[battle rifle]]s, while rifles that fire an intermediate cartridge are called [[assault rifle]]s.

Assault rifles are a compromise between the size and weight of a pistol-caliber submachine gun and a full-size battle rifle, firing intermediate cartridges and allowing semi-automatic and burst or full-automatic fire options (selective fire), sometimes with both of the latter presents.