Automatic firearm in the context of Action (firearms)

A SWAT (Special Weapons and Tactics) team is a generic term for a police tactical unit within the United States, though the term has also been used by other nations.

SWAT units are generally trained, equipped, and deployed to resolve "high-risk situations", often those regular police units are not trained or equipped to handle, such as shootouts, standoffs, raids, hostage-takings, and terrorism. SWAT units are equipped with specialized weapons and equipment not normally issued to regular police units, such as automatic firearms, high-caliber sniper rifles, stun grenades, body armor, ballistic shields, night-vision devices, and armored vehicles, among others. SWAT units are often trained in special tactics such as close-quarters combat, door breaching, crisis negotiation, and de-escalation.

A submachine gun (SMG) or sub-gun 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 automatic firearm with notably less firepower than a machine gun (hence the prefix "sub-"). As a machine gun must fire rifle cartridges to be classified as such, submachine guns are not considered machine guns.

In the 20th century, the submachine gun was developed during World War I (1914–1918) as a close quarter offensive weapon, mainly for trench raiding. At its peak during World War II (1939–1945), millions of submachine guns were made for assault troops and auxiliaries whose doctrines emphasized close-quarter suppressive fire. New submachine gun designs appeared frequently during the Cold War, especially among special forces, commandos and mechanized infantrymen. Submachine gun usage for frontline combat decreased in the 1980s and 1990s.

A machine gun (MG) is a fully automatic and rifled firearm designed for sustained direct fire. Automatic firearms of 20 mm (0.79 in) caliber or more are classified as autocannons rather than machine guns.

As a class of military kinetic projectile weapons, machine guns are designed to be mainly used as infantry support weapons and generally used when attached to a bipod or tripod, a fixed mount or a heavy weapons platform for stability against recoil. Many machine guns also use belt feeding and open bolt operation, features not normally found on other infantry firearms.

An autocannon, automatic cannon, machine cannon or anti-tank machine gun, is a fully automatic gun that is capable of rapid-firing large-caliber (20 mm/0.79 in or more) armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bullets) fired by a machine gun. Autocannons have a longer effective range and greater terminal performance than machine guns, due to the use of larger/heavier munitions (most often in the range of 20–60 mm (0.79–2.36 in), but bigger calibers also exist), but are usually smaller than tank guns, howitzers, field guns, or other artillery. When used on its own, the word "autocannon" typically indicates a non-rotary weapon with a single barrel. When multiple rotating barrels are involved, such a weapon is referred to as a "rotary autocannon" or "rotary cannon". If it uses a single barrel with a rotating cylinder with multiple chambers, it is known as a "revolver autocannon" or "revolver cannon"; both of these systems are commonly used as aircraft guns and anti-aircraft guns.

Autocannons are heavy weapons that are unsuitable for use by infantry. Due to the heavy weight and recoil, they are typically installed on fixed mounts, wheeled carriages, ground combat vehicles, aircraft, or watercraft, and are almost always crew-served, or even remote-operated with automatic target recognition/acquisition (e.g. sentry guns and naval CIWS). As such, ammunition is typically fed from a belt system to reduce reloading pauses or for a faster rate of fire, but magazines remain an option. Common types of ammunition, among a wide variety, include HEIAP, HEDP and more specialised armour-piercing (AP) munitions, mainly composite rigid (APCR) and discarding sabot (APDS) rounds.

An intermediate cartridge is a rifle/carbine cartridge that has significantly greater power than a pistol cartridge but still has a reduced muzzle energy compared to fully powered cartridges (such as the .303 British, 7.62×54mmR, 7.65×53mm Mauser, 7.92×57mm Mauser, 7.7×58mm Arisaka, .30-06 Springfield, or 7.62×51mm NATO), and therefore is regarded as being "intermediate" between traditional rifle and handgun cartridges.

As their recoil is significantly reduced compared to full-power cartridges, fully automatic rifles firing intermediate cartridges are relatively easy to control. However, even though they are less powerful than a traditional full-power cartridge, the external ballistics are still sufficient for an effective range of 300–600 metres (330–660 yd), which covers most typical infantry engagement situations in modern warfare. This allowed for the development of the assault rifle, a type of versatile selective fire small arms that is lighter and more compact than traditional battle rifles that fire full-power cartridges.

A shooting range, firing range, gun range or shooting ground is a specialized facility, venue, or field designed specifically for firearm usage qualifications, training, practice, or competitions. Some shooting ranges are operated by military or law enforcement agencies, though the majority of ranges are privately owned by civilians and sporting clubs and cater mostly to recreational shooters. Each facility is typically overseen by one or more supervisory personnel, known as a Range Officer (RO), or sometimes a range master in the United States. Supervisory personnel are responsible for ensuring that all safety rules and relevant laws are followed at all times.

Shooting ranges can be indoor or outdoor, and may be restricted to certain types of firearm that can be used such as handguns or long guns, or they can specialize in certain Olympic disciplines such as trap/skeet shooting or 10 m air pistol/rifle. Most indoor ranges restrict the use of high-power calibers, rifles, or fully automatic firearms.

A machine pistol is a handgun that is capable of fully automatic fire, including stockless handgun-style submachine guns.

The Austrians introduced the world's first machine pistol, the Steyr Repetierpistole M1912/P16, during World War I. The Germans also experimented with machine pistols, by converting various types of semi-automatic pistols to full-auto, leading to the development of the first practical submachine guns. During World War II, machine pistol development was widely disregarded in favor of submachine gun mass-production. After the war, machine pistol development was limited and only a handful of manufacturers would develop new designs, with varying degrees of success. This concept would eventually lead to the development of the personal defense weapon or PDW.

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 released or ammunition runs out. Automatic shotguns have a very limited range, but provide tremendous firepower at close range.

The M4 carbine (officially Carbine, Caliber 5.56 mm, M4) is an assault rifle developed in the United States during the 1980s. It is a shortened version of the M16A2 assault rifle. The M4 is extensively used by the US military, which decided to largely replace the M16 rifle in US Army (starting 2010) and US Marine Corps (starting 2016) combat units as the primary infantry weapon and service rifle. The M4 has been adopted by over 60 countries worldwide, and has been described as "one of the defining firearms of the 21st century".

Since its adoption in 1994, the M4 has undergone over 90 modifications to improve the weapon's adaptability, ergonomics and modularity, including: the M4A1, which possesses a thicker barrel and a replacement of the burst-fire control group with a fully automatic one; the SOPMOD, an accessory kit containing optical attachments; and the underbarrel weapons such as M203 and M320 grenade launchers to the Masterkey and M26-MASS shotguns.

A rotary cannon, rotary autocannon, gatling cannon, or gatling autocannon, is any large-caliber multiple-barreled automatic firearm that uses a Gatling-type rotating barrel assembly to deliver a sustained saturational direct fire at much greater rates of fire than single-barreled autocannons of the same caliber. The loading, firing and ejection functions are performed simultaneously in different barrels as the whole assembly rotates, and the rotation also permits the barrels some time to cool. Rotary cannons, external or self-driven are used in aircraft over reciprocating bolt autocannons which are more prone to jamming in high g environments. The rotating barrels on nearly all modern Gatling-type guns are powered by an external force such as an electric motor, although internally powered gas-operated versions have also been developed.

The cyclic multi-barrel design synchronizes the firing/reloading sequence. Each barrel fires a single cartridge when it reaches a certain position in the rotation, after which the spent casing is ejected at a different position and then a new round is loaded at another position. During the cycle, the barrel has more time to dissipate some heat away to the surrounding air.

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 burst-fire as well). Automatic rifles are distinguished from semi-automatic rifles in their ability to fire more than one shot in succession once the trigger is pulled. Most automatic rifles are further subcategorized as battle rifles or assault rifles.

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.

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.

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 to fifty or more rounds on autocannons, with a single pull of the trigger. This firing mode is commonly used in submachine guns and assault rifles. Other types of firearms, such as machine pistols, including the Heckler & Koch VP70 and Beretta 93R also have a burst mode.

The burst mode is normally employed as an intermediate fire mode between semi-automatic and fully automatic, although some firearms lack a "full auto" capability and use a burst mode instead. For instance, the M16A4 (the standard-issue service rifle of the USMC) has, in addition to the semi-automatic mode, a three-round burst mode, which replaced the fully automatic mode of the previous M16A1 and M16A3 models. The reason for this replacement was the massive waste of ammunition and very poor performance of soldiers who fired their rifles in fully automatic mode during the Vietnam War.

A submachine gun (SMG) or sub-gun 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 automatic firearm with notably less firepower than a machine gun (hence the prefix "sub-"). As a machine gun must fire rifle cartridges to be classified as such, submachine guns are not considered machine guns.

In the 20th century, the submachine gun was developed during World War I (1914–1918) as a close-quarter offensive weapon, mainly for trench raiding. At its peak during World War II (1939–1945), millions of submachine guns were made for assault troops and auxiliaries whose doctrines emphasized close-quarter suppressive fire. New submachine gun designs appeared frequently during the Cold War, especially among special forces, commandos and mechanized infantrymen. Submachine gun usage for frontline combat decreased in the 1980s and 1990s.

A designated marksman rifle (DMR) is a modern scoped high-precision rifle used by infantry in the designated marksman (DM) role. It generally fills the engagement range gap between a service rifle and a dedicated sniper rifle, at around 300–600 metres (330–660 yd).

DMRs are distinguished from sniper rifles in that they are semi-automatic to provide higher rates of fire (with some also having selective fire to switch to burst or automatic) and have larger magazine capacities (10, 20, or 30 rounds depending on the firearm and operational requirements) to allow rapid engagement of multiple targets.