An automatic firearm is an auto-loading

firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China, when bamboo tubes ...

that continuously

chambers Chambers may refer to: Places Canada: *Chambers Township, Ontario United States: *Chambers County, Alabama * Chambers, Arizona, an unincorporated community in Apache County * Chambers, Nebraska * Chambers, West Virginia * Chambers Township, Hol ...

and fires rounds when the

trigger Trigger may refer to: Notable animals and people ;Mononym * Trigger (horse), owned by cowboy star Roy Rogers ;Nickname * Trigger Alpert (1916–2013), American jazz bassist * "Trigger Mike" Coppola (1900–1966), American gangster ;Surname * Bru ...

mechanism is actuated. The

action Action may refer to: * Action (narrative), a literary mode * Action fiction, a type of genre fiction * Action game, a genre of video game Film * Action film, a genre of film * ''Action'' (1921 film), a film by John Ford * ''Action'' (1980 fil ...

of an automatic firearm is capable of harvesting the excess energy released from a previous discharge to feed a new ammunition

round Round or rounds may refer to: Mathematics and science * The contour of a closed curve or surface with no sharp corners, such as an ellipse, circle, rounded rectangle, cant, or sphere * Rounding, the shortening of a number to reduce the number ...

into the

chamber Chamber or the chamber may refer to: In government and organizations * Chamber of commerce, an organization of business owners to promote commercial interests *Legislative chamber, in politics * Debate chamber, the space or room that houses delib ...

, and then ignite the propellant and discharge the projectile (either

bullet A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. Bullets are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax. Bullets are made in various shapes and co ...

shot Shot may refer to: Arts, entertainment, and media * ''Shot'' (album), by The Jesus Lizard *''Shot, Illusion, New God'', an EP by Gruntruck *'' Shot Rev 2.0'', a video album by The Sisters of Mercy * "Shot" (song), by The Rasmus * ''Shot'' (2017 f ...

, or slug) by delivering a hammer or striker impact on the

primer Primer may refer to: Arts, entertainment, and media Films * ''Primer'' (film), a 2004 feature film written and directed by Shane Carruth * ''Primer'' (video), a documentary about the funk band Living Colour Literature * Primer (textbook), a t ...

. If ''both'' the feeding and ignition procedures are automatically cycled, the weapon will be considered "fully automatic" and will fire continuously as long as the trigger is kept depressed and the ammunition feeding (either from a

magazine A magazine is a periodical publication, generally published on a regular schedule (often weekly or monthly), containing a variety of content. They are generally financed by advertising, purchase price, prepaid subscriptions, or by a combinatio ...

or a

belt Belt may refer to: Apparel * Belt (clothing), a leather or fabric band worn around the waist * Championship belt, a type of trophy used primarily in combat sports * Colored belts, such as a black belt or red belt, worn by martial arts practit ...

) remains available. In contrast, a firearm is considered " semi-automatic" if it only automatically cycles to chamber new rounds (i.e.

self-loading 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 follow ...

) but does not automatically fire off the shot unless the user manually resets (usually by releasing) and re-actuates the trigger, so only one round gets discharged with each individual trigger-pull. A burst-fire firearm is an "in-between" of fully and semi-automatic firearms, firing a brief continuous "burst" of multiple rounds with each trigger-pull, but then will require a manual re-actuation of the trigger to fire another burst. Automatic firearms are further defined by the type of cycling principles used, such as

recoil operation Recoil operation is an operating mechanism used to implement locked breech, autoloading firearms. Recoil operated firearms use the energy of recoil to cycle the action, as opposed to gas operation or blowback operation using the pressure of the p ...

, blowback,

blow-forward Blow-forward is a firearm action where the propellant gas pressure and the friction of the bullet traveling down the bore drag the whole gun barrel forward to facilitate the opening of the breech. This forward barrel motion provides most ...

gas operation Gas-operation is a system of operation used to provide energy to operate locked breech, autoloading firearms. In gas-operation, a portion of high-pressure gas from the cartridge being fired is used to power a mechanism to dispose of the spent ...

Rates of fire

Cyclic rate

Self-loading firearms are designed with varying rates of fire due to having different purposes. The speed with which a self-loading firearm can cycle through the functions of: #Fire #Eject #Load #Cock is referred to as its cyclic rate. In fully automatic firearms, the cyclic rate is tailored to the purpose the firearm is intended to serve. Anti-aircraft machine guns often have extremely high rates of fire to maximize the probability of a hit. In infantry support weapons, these rates of fire are often much lower and in some cases, vary with the design of the particular firearm. The

MG 34 The MG 34 (shortened from German: ''Maschinengewehr 34'', or "machine gun 34") is a German recoil-operated air-cooled general-purpose machine gun, first tested in 1929, introduced in 1934, and issued to units in 1936. It introduced an entirely n ...

is a

WWII World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

-era machine gun which falls under the category of a "general purpose machine gun". It was manufactured in several variations: with a cyclic rate as high as 1200 rounds per minute, but also in an infantry model which fired at 900 rounds per minute.

Effective rate of fire

Continuous fire generates high temperatures in a firearm's barrel and increased temperatures throughout most of its structure. If fired continuously, the components of the firearm will eventually suffer structural failure. All firearms, whether they are semi-automatic, fully automatic, or otherwise, will overheat and fail if fired indefinitely. This issue tends to present itself primarily with fully automatic fire. For example, the MG34 may have a calculated cyclic rate of 1200 rounds per minute, but is likely to overheat and fail in the space of one minute of continuous fire. Semi-automatic firearms may also overheat if continuously fired. Recoil plays a significant role in the time it takes to reacquire one's sight picture, ultimately reducing the effective rate of fire.

Automatic firearm types

Automatic firearms can be divided into six main categories: ;

Automatic rifle An automatic rifle is a type of autoloading rifle that is capable of fully automatic fire. Automatic rifles are generally select-fire weapons capable of firing in semi-automatic and automatic firing modes (some automatic rifles are capable of ...

: The standard type of

service rifle A service rifle (or standard-issue rifle) is a rifle a military issues to regular infantry. In modern militaries, this is typically a versatile and rugged battle rifle, assault rifle, or carbine suitable for use in nearly all environments. Mos ...

s in most modern militaries, usually capable of selective fire. Assault rifles are a specific type of select-fire rifle chambered in an intermediate cartridge and fed via a high-capacity detachable magazine.

Battle rifle A battle rifle is a service rifle chambered to fire a fully powered cartridge. The term "battle rifle" is a retronym created largely out of a need to better differentiate the intermediate cartridge, intermediate-powered assault rifles (e.g. the S ...

s are similar, but chambered in a full-powered cartridge. ;

Automatic shotgun An automatic shotgun is an automatic firearm that fires shotgun shells (thereby making it a shotgun) and uses some of the energy of each shot to automatically cycle the action and load a new round. It will fire repeatedly until the trigger is rel ...

: A type of

combat shotgun A combat shotgun is a shotgun issued by militaries for warfare. The earliest shotguns specifically designed for combat were the trench guns or trench shotguns issued in World War I. While limited in range, the multiple projectiles typically us ...

capable of firing shotgun shells automatically, usually also semi-automatically. ;

Machine gun A machine gun is a fully automatic, rifled autoloading firearm designed for sustained direct fire with rifle cartridges. Other automatic firearms such as automatic shotguns and automatic rifles (including assault rifles and battle rifles) a ...

: A large group of heavier firearms used for suppressive automatic fire of rifle cartridges, usually attached to a mount or supported by a bipod. Depending on size, weight and role, machine guns are divided into

heavy Heavy may refer to: Measures * Heavy (aeronautics), a term used by pilots and air traffic controllers to refer to aircraft capable of 300,000 lbs or more takeoff weight * Heavy, a characterization of objects with substantial weight * Heavy, ...

medium Medium may refer to: Science and technology Aviation *Medium bomber, a class of war plane *Tecma Medium, a French hang glider design Communication * Media (communication), tools used to store and deliver information or data * Medium of ...

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...

machine guns. The ammunition is often

belt-fed upright=1.35, An M60 machine gun belt loaded with 7.62×51mm NATO cartridges, aboard a U.S. Navy">7.62×51mm_NATO.html" ;"title="M60 machine gun belt loaded with 7.62×51mm NATO">M60 machine gun belt loaded with 7.62×51mm NATO cartridges, aboar ...

. ;

Submachine gun A submachine gun (SMG) is a magazine-fed, automatic carbine designed to fire handgun cartridges. The term "submachine gun" was coined by John T. Thompson, the inventor of the Thompson submachine gun, to describe its design concept as an autom ...

: An automatic, short rifle (

carbine A carbine ( or ) is a long gun that has a barrel shortened from its original length. Most modern carbines are rifles that are compact versions of a longer rifle or are rifles chambered for less powerful cartridges. The smaller size and lighte ...

) typically chambered for

pistol A pistol is a handgun, more specifically one with the chamber integral to its gun barrel, though in common usage the two terms are often used interchangeably. The English word was introduced in , when early handguns were produced in Europe, an ...

cartridges. Today seldom used in military contexts due to a rise in the use of body armor, they are commonly used by police forces and

close protection A bodyguard (or close protection officer/operative) is a type of security guard, government law enforcement officer, or servicemember who protects a person or a group of people — usually witnesses, high-ranking public officials or officers, ...

units in many parts of the world. ;

Personal defense weapon Personal defense weapons (PDWs) are a class of firearms intended for self-defense and security rather than warfare and infantry. Most PDWs fire a small-caliber (less than ), centerfire bottleneck cartridge resembling a scaled-down intermedia ...

: A new breed of automatic firearms that combines the light weight and size of the submachine gun with the medium power caliber ammunition of the rifle, thus in practice creating a submachine gun with body armor penetration capability. ;

Machine pistol A machine pistol is an autoloading pistol capable of fully automatic fire. The term can also be used to describe a stockless handgun-style submachine gun. The term is a calque of ''Maschinenpistole'', the German word for submachine guns. Machine ...

: A

handgun A handgun is a short- barrelled gun, typically a firearm, that is designed to be usable with only one hand. It is distinguished from a long gun (i.e. rifle, shotgun or machine gun, etc.), which needs to be held by both hands and also braced ...

-style firearm, capable of fully automatic or

burst fire In automatic firearms, burst mode or burst-fire is a firing mode enabling the shooter to fire a predetermined number of rounds, usually two or three rounds on hand held weapons and 50-100+ on anti-aircraft weapons and autocannons, with a single ...

. They are sometimes equipped with a foldable shoulder stock, to promote accuracy during automatic fire, creating similarities to their submachine gun counterparts. Some machine pistols are shaped similarly to semi-automatics (e.g., the

Glock 18 Glock is a brand of polymer- framed, short recoil-operated, locked-breech semi-automatic pistols designed and produced by Austrian manufacturer Glock Ges.m.b.H. The firearm entered Austrian military and police service by 1982 after it was the ...

Beretta 93R The Beretta 93R is an Italian selective-fire machine pistol, designed and manufactured by Beretta in the late 1970s for police and military use, that is derived from their semi-automatic Beretta 92. The "R" stands for ''Raffica'', which is It ...

). As with SMGs, machine pistols fire pistol caliber cartridges (such as the 9mm,

.40 The .40 S&W is a rimless pistol cartridge developed jointly by American firearms manufacturers Smith & Wesson and Winchester in 1990. The .40 S&W was developed as a law enforcement cartridge designed to duplicate performance of the Federal B ...

.45 ACP The .45 ACP ( Automatic Colt Pistol) or .45 Auto (11.43×23mm) is a rimless straight-walled handgun cartridge designed by John Moses Browning in 1904, for use in his prototype Colt semi-automatic pistol. After successful military trials, it ...

etc.).

Burst mode

Burst Automatic is an Automatic Fire mode, it is typically used to limit the number of rounds fired, due to the inaccuracy of fully automatic fire. In the US M16/M4 platforms, the burst mode fires three rounds per trigger reset. The rifle will not fire again until the trigger is released and pulled again. There are suggestions that fully automatic fire has no genuine benefit and has been restricted or banned in combat due to being a waste of ammunition. The M4 carbine is now the main combat rifle of the US armed forces and has been available until recently in semi-automatic and burst mode of three rounds only.

Regulation

Automatic weapons tend to be restricted to

military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...

and

police The police are a constituted body of persons empowered by a state, with the aim to enforce the law, to ensure the safety, health and possessions of citizens, and to prevent crime and civil disorder. Their lawful powers include arrest and t ...

organizations in most developed countries that permit the use of semi-automatic firearms. Where automatic weapons are permitted, restrictions and regulations on their possession and use may be much more severe than for other firearms. In the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, taxes and strict regulations affect the manufacture and sale of fully automatic firearms under the

National Firearms Act The National Firearms Act (NFA), 73rd Congress, Sess. 2, ch. 757, was enacted on June 26, 1934, and currently codified and amended as . The law is an Act of Congress in the United States that, in general, imposes an excise tax on the manufact ...

of 1934 and the closing of the "machine gun" registry by the Firearm Owners Protection Act of 1986 (only previously registered automatic weapons may be purchased). A prospective user must go through an application process administered by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), which requires a federal tax payment of $200 and a thorough criminal

background check A background check is a process a person or company uses to verify that an individual is who they claim to be, and this provides an opportunity to check and confirm the validity of someone's criminal record, education, employment history, and oth ...

. The tax payment buys a

revenue stamp A revenue stamp, tax stamp, duty stamp or fiscal stamp is a (usually) adhesive label used to designate collected taxes or fees on documents, tobacco, alcoholic drinks, drugs and medicines, playing cards, hunting licenses, firearm registration, ...

, which is the legal document allowing possession of an automatic firearm. The use of a

gun trust The National Firearms Act (NFA), 73rd Congress, Sess. 2, ch. 757, was enacted on June 26, 1934, and currently codified and amended as . The law is an Act of Congress in the United States that, in general, imposes an excise tax on the manufactu ...

to register with the ATF has become an increasingly popular method of acquisition and ownership of automatic firearms.

Similar weapons

Other similar weapons not usually referred to as automatic firearms include the following: *

Autocannon An autocannon, automatic cannon or machine cannon is a fully automatic gun that is capable of rapid-firing large-caliber ( or more) armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bull ...

, which are 15 mm or greater in bore diameter and thus considered cannons, not small arms. * Gatling guns, multiple-barrel designs, often used with external power supplies to generate rates of fire higher than automatic firearms.

References

{{Reflist Firearm actions *