Automatic firearm

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A M2 Browning machine gun, surrounded by ejected cartridge cases

An automatic firearm or fully automatic firearm (to avoid confusion with semi-automatic firearms) is an autoloading firearm that continuously chambers and fires rounds when the trigger mechanism is actuated. The action of an automatic firearm is capable of harvesting the excess energy released from a previous discharge to feed a new ammunition round into the chamber, and then igniting the propellant and discharging the projectile (either bullet, shot, or slug) by delivering a hammer or striker impact on the primer.

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

self-loading) 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.[1] 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

gas operation
.

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:

  1. Fire
  2. Eject
  3. Load
  4. 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

WWII-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.[2]

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.[3]

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.[4]

Automatic firearm types

A United States Army soldier laying automatic suppressive fire with an M60 machine gun during the Vietnam War

Automatic firearms can be divided into six main categories:

Automatic rifle
The standard type of service rifles 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 rifles are similar, but chambered in a full-powered cartridge.[5]
Automatic shotgun
A type of combat shotgun capable of firing shotgun shells automatically, usually also semi-automatically.[5]
Machine gun
A large group of heavier firearms used for
belt-fed.[5]
Submachine gun
An automatic, short rifle (
close protection units in many parts of the world.[5]
Personal defense weapon
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.[5]
Machine pistol
A
.40, .45 ACP etc.).[5]

Burst mode

Burst mode is an automatic fire mode that limits the number of rounds fired with each trigger pull, most often to three rounds. After the burst is fired, the firearm will not fire again until the trigger is released and pulled again. Burst mode was implemented into firearms due to the inaccuracy of fully automatic fire in combat, and due to suggestions that fully automatic fire has no genuine benefit. Additionally, many militaries have restricted automatic fire in combat due to the ammunition wasted.[6]

Regulation

See also: Gun Control Act of 1968

Possession of automatic firearms tends to be restricted to members of

gun trust to register with the ATF has become an increasingly popular method of acquisition and ownership of automatic firearms.[why?
]

Similar weapons

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

  • Autocannon, 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.

See also

References

  1. ^ a b Carter, Gregg Lee (2012). Guns in American Society: An Encyclopedia of History, Politics, Culture, and the Law. ABC-CLIO. p. 53.
    ISBN 978-0-313-38670-1
    .
  2. ^ "Maschinengewehr Modell 34 (MG34) General Purpose Machine Gun (GPMG)". militaryfactory.com. Retrieved 3 March 2017.
  3. ^ "M240B - Machine Gun". armystudyguide.com. Archived from the original on 18 February 2017. Retrieved 3 March 2017.
  4. ^ "Maintaining a Sustained Rate or Fire". thefirearmblog.com. 3 August 2012. Retrieved 3 March 2017.
  5. ^
    ISBN 978-1-4402-2482-9
    .
  6. ^ "Full Auto: Battlefield Necessity or A Waste of Ammo?". military.com. Retrieved 3 March 2017.
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