A
semi-automatic, or
self-loading firearmA firearm is a device which projects either single or multiple projectiles at high velocity through a controlled explosion. The firing is achieved by the gases produced through rapid, confined burning of a propellant. This process of rapid burning is technically known as deflagration...
is a gun that after being fired, ejects the empty
roundA cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim ....
that has been fired, loads a new cartridge, and cocks itself. This mechanism is different from a single-action
revolverA revolver is a repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing. As the user cocks the hammer, the cylinder revolves to align the next chamber and round with the hammer and barrel, which gives this type of firearm its name...
, a
pump-actionA pump-action rifle or shotgun is one in which the handgrip can be pumped back and forth in order to eject a spent round of ammunition and to chamber a fresh one. It is much faster than a bolt-action and somewhat faster than a lever-action, as it does not require the trigger hand to be removed from...
firearm, a
bolt-actionThe term bolt action refers to a type of firearm action in which the weapon's bolt is operated manually by the opening and closing of the breech with a small handle, most commonly placed on the right-hand side of the weapon...
firearm, or a
lever-actionLever-action is a type of firearm action which uses a lever located around the trigger guard area to load fresh cartridges into the chamber of the barrel when the lever is worked...
firearm; all of which require the shooter to cock the weapon manually before each shot and eject each empty
roundA cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim ....
afterwards (these are called repeating fireams). For example, to fire ten rounds in a semi-automatic firearm, the trigger would need to be pulled ten times (once for each round fired) without cocking the weapon manually in between shots, in contrast to a
fully automatic firearmAn automatic firearm is a firearm that fires, automatically extracts the used cartridge case from the barrel and ejects it, then loads a new case into the barrel; generally by harnessing the recoil of the cartridge's explosion...
, which can continue to fire as long as the trigger is held or until it runs out of
ammunitionAmmunition, often informally referred to as ammo, is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions...
.
Semi-automatic rifle
The first successful design for a semi-automatic rifle is attributed to German-born gunsmith Ferdinand Ritter von Mannlicher, who unveiled the design in 1885. The Model 85 was followed by the equally innovative Mannlicher Models 91, 93 and 95 semi-automatic rifles. Although Mannlicher earned his reputation with his bolt action rifle designs, he also produced a few semi-automatic pistols, including the
Steyr Mannlicher M1894The M1894 Steyr Mannlicher blow-forward, semi-automatic pistol was an early semi-automatic pistol.-General features:This earliest Steyr Mannlicher pistol, manufactured by FAB.D'ARMES Neuhausen, Switzerland, was designed to be self loading and to use a special rimmed cartridge in 6.5 mm caliber...
, which employed an unusual blow-forward action and held five rounds of 6.5 mm ammunition that were fed into the M1894 by a
stripper clipA stripper clip or charger is a speedloader that holds several cartridges together in a single unit for easier loading of a firearm's magazine. A stripper clip is used only for loading the magazine and is not necessary for the firearm to function...
.
Semi-automatic shotgun
A few years later, American gunsmith
John Moses BrowningJohn Moses Browning , born in Ogden, Utah, was an American firearms designer who developed many varieties of firearms, cartridges, and gun mechanisms, many of which are still in use around the world...
developed the first successful semi-automatic shotgun, the
Browning Auto-5The Browning Automatic 5, most often Auto-5 or simply A-5, is a recoil-operated autoloading shotgun designed by John Browning. It was the first successful autoloading shotgun designed and remained in production until 1998...
, which was first manufactured in 1902 by
Fabrique Nationale de HerstalFabrique Nationale de Herstal, more often abbreviated as Fabrique Nationale or simply FN, is a Belgian manufacturer of firearms. The official company name is FN Herstal. FN is a subsidiary of the Herstal Group. Herstal also owns the U.S. Repeating Arms Company and Browning Arms Company...
and sold in America under the Browning name. The Auto-5 relied on
long recoil operationRecoil operation is an operating mechanism used in locked-breech, autoloading firearms. As the name implies, these actions use the force of recoil to provide energy to cycle the action. Other operating systems are blowback operated, gas operated, gatling, and chain.-Design:which is calculated...
; this design remained the dominant form in semi-automatic shotguns for approximately 50 years. Production of the Auto-5 was finally ceased in 1999.
Blowback semi-automatic
In 1903 and 1905, the Winchester Repeating Arms Company introduced the first semi-automatic rim-fire and center-fire rifles designed especially for the civilian market. The Winchester Model 1903 and Winchester Model 1905 operated on the principle of
delayed blowbackBlowback is a system of operation for self-loading firearms that obtains power from the motion of the cartridge case as it is pushed to the rear by expanding gases created by the ignition of the powder charge....
in order to function semi-automatically. Designed entirely by
T.C. JohnsonThomas Crosley Johnson, American firearms designer. Son of a President of the Yale Safe and Iron Company, Johnson was trained as a industrial engineer and worked for several companies before coming to the Winchester Repeating Arms Company...
, the Winchester Model 1903 achieved commercial success and continued to be manufactured to 1932 when the Winchester Model 63 replaced it.
By the early 20th century, several manufacturers had introduced semi-automatic .22 sporting rifles, including
WinchesterThe Winchester Repeating Arms Company was a prominent American maker of repeating firearms during the late nineteenth and early twentieth century.-Predecessors:...
,
RemingtonRemington Arms is a major American manufacturer of rifles, shotguns, other firearms, revolvers and ammunition. They also license the Remington name to hunting apparel, Arctic Cat ATV's, and other hunting and shooting products manufactured by other companies. It was founded in 1816 by Eliphalet...
, Fabrique Nationale and
Savage ArmsThe Savage Arms Company is a firearms manufacturing company based in Westfield, Massachusetts. The company makes a variety of rimfire and centerfire rifles, as well as marketing the Stevens single-shot rifles and shotguns...
, all using the direct blow-back system of operation. Winchester introduced a medium caliber semi-automatic sporting rifle, the model 1907 as an upgrade to the Model 1905, utilizing a delayed blowback system of operation, in calibers such as
.351 WinchesterThe .351 Winchester Self-Loading is an American rifle cartridge.Winchester introduced the .351SL in the Winchester Model 1907 self-loading rifle as a replacement for the Winchester Model 1905 and the .35SL...
. Both the Models of 1905 and 1907 saw limited military and police use.
Recoil Operated Rifles
In 1906, Remington Arms introduced the "Remington Auto-loading Repeating Rifle," also designed by Browning. Remington advertised this rifle, renamed the "Model 8" in 1911, as a sporting rifle. This is a locked breech, recoil operated action. The rifle was offered in .25, .30, .32, and .35 caliber models, and gained popularity among civilians as well as some law enforcement officials who appreciated the combination of semi-automatic action and relatively powerful rifle cartridges. The Model 81 superseded the Model 8 in 1936 and was offered in
.300 Savage.300 Savage cartridge is a rimless, .30 caliber rifle cartridge developed by the Savage Arms Company in 1920 which was designed to replace the less powerful .303 Savage in the their popular Savage Model 99 lever-action rifle...
as well as the original Remington calibers.
The first semi-automatic rifle adopted and used by a major military power (France) was the Fusil Automatique Modele 1917. This too is a locked breech, recoil operated action.It was the first general issue self-loading rifle and contained features that were seminal in its field. A number of features first found on the M1917 would later find their way into many later, more widely known, more widely produced designs. The M1917 was used in the latter stages of WWI and the Moroccan Rif war 1921-1926. Following World War I, the French military converted many of the M1917 to manual operation. The Lebel bolt action rifle remained the standard French infantry rifle until replaced in 1936 by the MAS.
Other nations experimented with self-loading rifles between the two World Wars, including Britain, which had intended to replace the bolt-action
Lee-EnfieldThe Lee-Enfield bolt-action, magazine-fed, repeating rifle was the main firearm used by the military forces of the British Empire/Commonwealth during the first half of the 20th century. It was the British Army's standard rifle from its official adoption in 1895 until 1957...
with a self-loader, possibly chambered for sub-caliber ammunition, but discarded that plan as the imminence of the Second World War and the emphasis shifted from replacing every rifle with a new design to speeding-up re-armament with existing weapons. The Soviet Union and Germany would both issue successful self-loading and selective-fire rifles on a large scale during the course of the war, but not in sufficient numbers to replace their standard bolt-action rifles.
Gas Operated Rifles
There was much experimentation between the World Wars in gas operated semi-automatic rifles, largely for military application.
The U.S. M1 Garand is generally recognised as the first semi-automatic rifle to replace its nation's bolt action rifle as the standard issue infantry rifle. The gas-operated M1 Garand was developed by Canadian-born
John GarandJohn Cantius Garand was a designer of firearms best known for creating the first successful semi-automatic rifle to be put into active military service, the M1 Garand....
for
Springfield ArmoryThe Springfield Armory was the primary center for the manufacture of U.S. military small arms and the site of many important technological advances in gun manufacture. Many different models produced at the armory from 1794 to 1968 were referred to as "Springfield rifles"...
, which was owned by the US government. After years of research and testing, the first production model of the M1 Garand was unveiled in 1937. During
World War IIWorld War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...
, the M1 Garand gave American infantrymen an overall advantage over their German opponents, of whom most were still issued the Mauser 98 bolt-action rifle.
The Russian Tokarev (SVT 38 and SVT 40 with more than 1 Millions produced) and German G43 semi-automatic gas operated rifles were issued in World War II in relatively small numbers and did not replace the bolt action rifle as a standard infantry weapon.
Another famous gas operated semi automatic rifle developed toward the end of WWII was the
SKSThe SKS is a Soviet 7.62x39mm caliber semi-automatic carbine, designed in 1945 by Sergei Gavrilovich Simonov. SKS is an acronym for Samozaryadniy Karabin sistemi Simonova , 1945 , or SKS 45...
. Designed by
Sergei Gavrilovich SimonovSergei Gavrilovich Simonov was a Soviet weapons designer; he is one of the fathers of the modern assault rifle.Mostly known for the Samozaryadnyi Karabin sistemi Simonova , 1945 , or SKS carbine, he also pioneered the assault and semi-automatic rifle field in the 1920s and 1930s,...
in 1945, it came equipped with a
bayonetA bayonet is a knife-, dagger-, sword-, or spike-shaped weapon designed to fit on, over or underneath the muzzle of a rifle barrel or similar weapon, effectively turning the gun into a spear. It is a close quarter battle combat or last-resort weapon.-History: The origins of the bayonet are...
and could hold ten rounds fed by a stripper clip. It didn't see very much combat, since it was quickly replaced by the
AK-47The AK-47 is a selective fire, gas operated 7.62mm assault rifle developed in the Soviet Union by Mikhail Kalashnikov in the 1940s. Six decades later, the AK-47 and its variants and derivatives remain in service throughout the world...
. It was the first weapon chambered to use the cartridge
7.62x39mmThe 7.62x39mm rifle cartridge was designed during World War II and first used in the SKS carbine by the Soviet Union.The cartridge was likely influenced by a variety of foreign developments, especially the pre-war German GeCo, 7.75x39mm experimental round, and possibly by the late-war German...
, which had a medium amount of recoil.
Semi-automatic weapons
There are semi-automatic pistols,
rifleA semi-automatic rifle is a type of rifle that fires a single bullet each time the trigger is pulled, automatically ejects the spent cartridge, chambers a fresh cartridge from its magazine, and is immediately ready to fire another shot...
s, and
shotgunA semi-automatic shotgun is a form of shotgun that is able to fire a cartridge after every trigger squeeze, without any manual chambering of another round being required...
s designed and made as semi-automatic only.
Selective fireA selective fire firearm fires semiautomatically and at least one automatic mode by means of a selector depending on the weapons design. Some selective fire weapons utilize burst fire mechanisms to limit the maximum or total number of shots fired automatically in this mode...
firearms are capable of both full automatic and semi-automatic modes.
Semi-automatic
Semi-automatic refers to a firearms which uses the force of recoil or gas to eject the empty catridge casing and load a cartridge in the firing chamber for the next shot and which allows repeat shots solely through the action of pulling the trigger. A double-action revolver also requires only a trigger pull for each round that is fired but is not considered semi-automatic since the firing chambers of a revolver are manually loaded, not self loaded.
Fully Automatic compared to Semi-automatic
The usage of the term
automatic may vary according to context. Gun specialists point out that the word
automatic is sometimes misunderstood to mean
fully automatic fireAn automatic firearm is a firearm that fires, automatically extracts the used cartridge case from the barrel and ejects it, then loads a new case into the barrel; generally by harnessing the recoil of the cartridge's explosion...
when used to refer to a self-loading, semi-automatic firearm not capable of fully automatic fire. In this case,
automatic refers to the loading mechanism, not the firing capability.
The term "automatic pistol" almost exclusively refers to a semi-automatic (i.e. not fully automatic) pistol. With handguns, the term "automatic" is commonly used to distinguish semi-automatic pistols from revolvers. The term "auto-loader" may also be used to describe a semi-automatic handgun. However, the term "automatic rifle" may mean a rifle capable of fully automatic fire. Both uses of the term "automatic" can be found, and the exact meaning must be determined from context.
Semi-automatic
The mechanism of semi-automatic (or auto-loading) firearms is usually what is known as a
closed boltA semi or fully-automatic firearm which is said to fire from a closed bolt is one where, when ready to fire, a round is in the chamber and the bolt and working parts are forward...
firing system. In a closed-bolt system, a round must first be chambered manually before the weapon can fire. When the trigger is pulled, only the hammer and
firing pinA firing pin or striker is part of the firing mechanism used in a firearm or explosive device e.g. an M14 landmine or bomb fuze. Firing pins may take many forms, though the types used in landmines, bombs, grenade fuzes or other single-use devices generally have a sharpened point...
move, striking and firing the cartridge. The bolt then recoils far enough rearward to extract and load a new cartridge from the
magazineA magazine is an ammunition storage and feeding device within or attached to a repeating firearm. Magazines may be integral to the firearm or removable . The magazine functions by moving the cartridges stored in the magazine into a position where they may be loaded into the chamber by the ...
into the firearm's chamber, ready to fire again once the trigger is pulled.
An
open boltA semi or fully automatic firearm is said to fire from an open bolt if, when ready to fire, the bolt and working parts are held to the rear. When the trigger is pulled the bolt goes forward, feeding a round from the magazine into the chamber and firing it...
mechanism is a common characteristic of fully automatic firearms. With this system, pulling the trigger releases the bolt from a cocked, rearward position, pushing a cartridge from the magazine into the chamber, firing the gun. The bolt retracts to the rearward position, ready to strip the next cartridge from the magazine. The open-bolt system is often used in
submachine gunA submachine gun is a firearm that combines the automatic fire of a machine gun with the cartridge of a pistol, and is usually between the two in weight and size...
s and other weapons with a high rate of fire. It is rarely used in semi-automatic-only firearms, which can fire only one shot with each pull of the trigger. The closed-bolt system is generally more accurate; since the center of gravity changes relatively little at the moment the trigger is pulled.
With full automatic weapons, open bolt operation allows air to circulate cooling the barrel; with semi-automatic firearms, the closed bolt operation is preferred as over-heating is not as critical, and accuracy is preferred in semi-automatic operation. Some select fire military weapons use open bolt in full automatic mode and closed bolt when semi-automatic is selected.
Problems
Semi-automatic firearms, though effective in combat, are also prone to many problems. The most notable of these problems is the
slamfireA slamfire is a premature, unintended discharge of a firearm that occurs as a round is being loaded into the chamber. Slamfires are most common in military firearms that have a free-floating firing pin, as opposed to a spring-loaded one. In the action of a typical semi-automatic weapon, the energy...
. This occurs when the bolt is released but the force of it closing is powerful enough to detonate the
primerPrimer can refer to:*Primer , a 1995 music album by the musical group Rockapella*Primer , a 2004 feature film written and directed by Shane Carruth...
. This may happen multiple times with a single magazine.
Like all auto loading firearms, most semi-automatics are also prone to jamming, on the feeding cycle when the cartridge gets stuck while entering the firing chamber or on the ejection cycle when the fired casing gets stuck while exiting the chamber.
See also
- AK-47
The AK-47 is a selective fire, gas operated 7.62mm assault rifle developed in the Soviet Union by Mikhail Kalashnikov in the 1940s. Six decades later, the AK-47 and its variants and derivatives remain in service throughout the world...
- AR-15
AR-15 is the common name for the widely owned semi-automatic rifle that is derived from the selective fire M16-series assault rifle, currently in use by the United States military....
- Assault weapons
- Military-Style Semi-Automatic
Military-style semi-automatic is a term in New Zealand firearms law with a similar meaning to that of assault weapon in the United States. The category was introduced after the 1990 Aramoana massacre, in which firearms fitting this definition were used....
- M110 Semi-Automatic Sniper System
- Pistol Slide
The slide is the part on the majority of semi-automatic pistols that moves during the operating cycle and generally houses the firing pin or striker, extractor, and serves as the bolt...
- M1 Garand
The M1 Garand was the first semi-automatic rifle to be generally issued to the infantry of any nation. Called "The Greatest Battle Implement Ever Devised" by General George S...
- M1911
The M1911 is a single-action, semi-automatic, magazine-fed, recoil-operated handgun chambered for the .45 ACP cartridge. It was designed by John M. Browning, and was the standard-issue side arm for the United States armed forces from 1911 to 1985, and is still carried by some U.S. forces. It was...
- Saiga-12
The Saiga-12 is a Kalashnikov-pattern 12 gauge combat shotgun available in a wide range of configurations. Like the Kalashnikov rifle variants, it is a rotating bolt, gas-operated gun that feeds from a box magazine...
- Selective fire
A selective fire firearm fires semiautomatically and at least one automatic mode by means of a selector depending on the weapons design. Some selective fire weapons utilize burst fire mechanisms to limit the maximum or total number of shots fired automatically in this mode...
- Semi-automatic pistol
- Semi-automatic rifle
A semi-automatic rifle is a type of rifle that fires a single bullet each time the trigger is pulled, automatically ejects the spent cartridge, chambers a fresh cartridge from its magazine, and is immediately ready to fire another shot...
- Semi-automatic shotgun
A semi-automatic shotgun is a form of shotgun that is able to fire a cartridge after every trigger squeeze, without any manual chambering of another round being required...
- SKS
The SKS is a Soviet 7.62x39mm caliber semi-automatic carbine, designed in 1945 by Sergei Gavrilovich Simonov. SKS is an acronym for Samozaryadniy Karabin sistemi Simonova , 1945 , or SKS 45...
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