Automatic rifle
An automatic rifle is a selective-fire infantry weapon capable of both semiautomatic and fully automatic modes, chambered in rifle cartridges such as .30-06 or 6.8mm, and designed to be carried and operated by a single soldier to provide mobile suppressive fire and enhance squad-level firepower during assaults.[1] The archetype of this weapon class is the M1918 Browning Automatic Rifle (BAR), a gas-operated, air-cooled, magazine-fed design patented by John M. Browning in 1917 and adopted by the U.S. Army in May 1918 for World War I service.[2][3] Weighing approximately 16 pounds empty with a 20-round detachable magazine and a 24-inch barrel, the BAR fired at rates up to 650 rounds per minute and proved instrumental in neutralizing enemy positions during key offensives like the Battle of St. Mihiel and the Meuse-Argonne campaign.[1][4] Its versatility allowed adaptation for light machine gun roles in World War II and the Korean War, where variants like the M1918A2 incorporated a bipod, flash suppressor, and dual automatic fire rates (300–450 or 500–650 rounds per minute), though it was gradually phased out by the 1960s in favor of newer designs like the M14 and M16 rifles.[2][1] In the post-Vietnam era, the role of the automatic rifle evolved within U.S. military doctrine to emphasize squad automatic weapons (SAWs), with the M249—chambered in 5.56mm NATO and belt-fed for sustained fire—serving as the primary automatic rifle in infantry squads since 1984, offering light machine gun capabilities while maintaining portability at around 17 pounds.[5] This weapon provides suppressive fire to support maneuver elements, with an effective range of up to 800 meters and a cyclic rate of 850 rounds per minute.[5] As of 2025, the U.S. Army is transitioning to the Next Generation Squad Weapon program, where the M250 Automatic Rifle—a lightweight, belt-fed, 6.8x51mm select-fire light machine gun weighing 13 pounds—replaces the M249 to improve lethality, accuracy, and range against modern body armor, featuring ambidextrous controls, a collapsible stock, M-LOK mounting, and a quick-detach suppressor.[6][7] Automatic rifles distinguish themselves from heavier belt-fed machine guns by their emphasis on individual portability and from assault rifles by often using full-power cartridges for greater range and penetration, though the lines have blurred with intermediate-caliber designs in contemporary forces.[6] Globally, similar weapons include the British L86 light support weapon and historical examples like the German MG 13, underscoring the automatic rifle's enduring role in enabling infantry to achieve fire superiority in close-quarters and maneuver warfare.[2]Definition and Classification
Core Definition
An automatic rifle is a type of autoloading rifle designed to be fired from the shoulder, capable of selective fire in either semiautomatic mode—where each trigger pull discharges one round—or fully automatic mode, where holding the trigger results in continuous fire until the magazine is depleted or the trigger is released. This distinguishes it from single-shot rifles, which require manual reloading after each round, and strictly semiautomatic rifles, which cannot sustain bursts of fire. Typically chambered in rifle-caliber ammunition, such as intermediate cartridges like 5.56×45mm NATO or full-power rounds like .30-06 Springfield, automatic rifles provide infantry with portable, high-volume firepower while maintaining the maneuverability of a standard rifle.[8] The core functionality relies on an ammunition feeding system, typically using detachable magazines or belts, that automatically cycles the action to chamber subsequent rounds, enabling sustained automatic fire for suppressive roles in combat. This capability sets automatic rifles apart from lighter automatic weapons like submachine guns, which use pistol cartridges, and crew-served machine guns that typically require fixed mounts or vehicle installation for sustained fire. Modern examples often incorporate ergonomic features for shoulder firing without external support, emphasizing mobility for individual or squad use.[5] Key components include the barrel, which guides and stabilizes the projectile; the receiver, housing the firing mechanism and serving as the rifle's structural frame; the bolt carrier group, which handles loading, locking, firing, and extraction of rounds; the fire control selector, allowing the shooter to switch between firing modes; and the magazine, a detachable box that stores and feeds ammunition into the chamber.[8] These elements work in concert to ensure reliable operation under varied conditions. The term "automatic rifle" originated in early 20th-century military nomenclature, first applied to designs like John Browning's prototype in 1917, initially termed the "Browning Machine Rifle" before standardization as the M1918 Browning Automatic Rifle (BAR), adopted by the U.S. Army in 1918 for its blend of rifle portability and automatic capability.[8]Distinctions from Related Firearms
Automatic rifles are distinguished from other firearms primarily by their selective-fire capability, which allows switching between semi-automatic and fully automatic modes, use of rifle-caliber ammunition, and design as individual infantry weapons for controlled bursts rather than sustained fire. In modern military usage, the lines between automatic rifles and light machine guns or squad automatic weapons have blurred, with weapons like the M249 SAW serving in the automatic rifle role while providing light machine gun capabilities.[5] In contrast, semi-automatic rifles lack full-automatic capability, firing only one round per trigger pull despite using similar rifle cartridges and serving individual users.[9] Assault rifles, a post-World War II subset, also feature selective fire but are chambered in intermediate cartridges for lighter weight and higher controllability during automatic fire.[10] Battle rifles share selective-fire mechanisms and individual use but employ full-power rifle cartridges, resulting in heavier designs suited for longer-range engagements.[11] Machine guns, while capable of full-automatic fire, are built for prolonged, sustained bursts, often belt-fed, and typically crew-served rather than handheld by a single soldier.[12] Submachine guns fire full-automatic but use pistol-caliber ammunition, limiting their range and penetration for close-quarters roles.[13]| Firearm Type | Fire Mode | Caliber Type | Intended Use |
|---|---|---|---|
| Automatic Rifle | Selective (semi/full-auto) | Rifle cartridge | Individual infantry, controlled bursts |
| Semi-Automatic Rifle | Semi-automatic only | Rifle cartridge | Individual, precision fire |
| Assault Rifle | Selective (semi/full-auto) | Intermediate cartridge | Individual, versatile combat |
| Battle Rifle | Selective (semi/full-auto) | Full-power rifle cartridge | Individual, long-range support |
| Machine Gun | Full-automatic (sustained) | Rifle or heavier | Typically crew-served, suppressive fire |
| Submachine Gun | Full-automatic | Pistol cartridge | Close-quarters, individual |