Asemi-automatic firearm, also called aself-loading orautoloading firearm (fully automatic andselective fire firearms are also variations onself-loading firearms), is arepeating firearm whoseaction mechanism automatically loads a following round ofcartridge into thechamber and prepares it for subsequent firing, but requires the shooter to manually actuate thetrigger 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 ofrecoil or high-pressure gas expanding within thebore) to unlock and move thebolt, 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 introducedsemi-automatic shotguns,rifles andpistols.
In military use, the semi-automaticM1911 handgun was adopted by the United States Army in 1911, and subsequently by many other nations. Semi-automatic rifles did not see widespread military adoption until just prior toWorld War II, theM1 Garand being a notable example. Modern service rifles such as theM4 carbine are often selective-fire, capable of semi-automatic and automatic orburst-fire operation. Civilian variants such as theAR-15 are generally semi-automatic only.
The first successful design for asemi-automatic rifle is attributed toAustria-born gunsmithFerdinand Ritter von Mannlicher, who unveiled the design in 1885.[1] The Model 85 was followed by the equally innovative Mannlicher Models 91, 93 and 95 semi-automatic rifles.[2] Although Mannlicher earned his reputation with hisbolt-action rifle designs, he also produced a few semi-automatic pistols, including theSteyr Mannlicher M1894, which employed an unusualblow-forward action and held five rounds of 6.5mm ammunition that were fed into the M1894 by astripper clip.
In 1902, American gunsmithJohn Moses Browning developed the first successfulsemi-automatic shotgun, theBrowning Auto-5, which was first manufactured byFabrique Nationale de Herstal and sold in America under the Browning name. The Auto-5 relied onlong recoil operation; this design remained the dominant form in semi-automatic shotguns for approximately 50 years. Production of the Auto-5 ended in 1998.
In 1903 and 1905, theWinchester Repeating Arms Company introduced the first semi-automaticrimfire andcenterfire rifles designed especially for the civilian market. TheWinchester Model 1903 andWinchester Model 1905 operated on the principle ofblowback in order to function semi-automatically. Designed entirely byT. C. Johnson, the Model 1903 achieved commercial success and continued to be manufactured until 1932 when the Winchester Model 63 replaced it.
By the early 20th century, several manufacturers had introduced semi-automatic .22 sporting rifles, includingWinchester,Remington, Fabrique Nationale andSavage Arms, all using the direct blow-back system of operation. Winchester introduced a medium caliber semi-automatic sporting rifle, theModel 1907 as an upgrade to the Model 1905, utilizing a blowback system of operation, in calibers such as.351 Winchester. Both the Models of 1905 and 1907 saw limited military and police use.
In 1906,Remington Arms introduced theRemington Auto-loading Repeating Rifle. Remington advertised this rifle, renamed the "Model 8" in 1911, as a sporting rifle. This is a locked-breech,long recoil action designed byJohn Browning. 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 a semi-automatic action and relatively powerful rifle cartridges. The Model 81 superseded the Model 8 in 1936 and was offered in.300 Savage as well as the original Remington calibers.
The first semi-automatic rifle adopted and widely issued by a major military power (France) was theFusil Automatique Modele 1917. This is a locked-breech, gas-operated action that is very similar in its mechanical principles to the futureM1 Garand in the United States. The M1917 was fielded during the latter stages ofWorld War I but it did not receive a favorable reception. However, its shortened and improved version, the Model 1918, was much more favourably received during the MoroccanRif War from 1920 to 1926. TheLebel bolt-action rifle remained the standard French infantry rifle until replaced in 1936 by theMAS-36 despite the various semi-automatic rifles designed between 1918 and 1935.
Other nations experimented with self-loading rifles between the two World Wars, including theUnited Kingdom, which had intended to replace the bolt-actionLee–Enfield 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. TheSoviet Union andNazi 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.
In 1937, the AmericanM1 Garand was the first semi-automatic rifle to replace its nation's bolt-action rifle as the standard-issue infantry weapon. Thegas-operated M1 Garand was developed by Canadian-bornJohn Garand for the U.S. government at theSpringfield Armory inSpringfield, Massachusetts. After years of research and testing, the first production model of the M1 Garand was unveiled in 1937. DuringWorld War II, the M1 Garand gave American infantrymen an advantage over their opponents, most of whom were issued slower firing bolt-action rifles.[3]
TheSovietAVS-36,SVT-38 and SVT-40 (originally intended to replace theMosin-Nagant as their standard service rifle), as well as the GermanGewehr 43, were semi-automaticgas-operated rifles issued duringWorld War II. In practice, they did not replace the bolt-action rifle as a standard infantry weapon.
Another gas-operated semi-automatic rifle developed toward the end of World War II was theSKS. Designed bySergei Gavrilovich Simonov in 1945, it came equipped with abayonet and could be loaded with ten rounds, using astripper clip. However, the SKS was quickly replaced by theAK-47, produced at around the same time, but with a 30-round magazine, and select fire capability. The SKS was the first widely issued weapon to use the7.62×39mm cartridge.[citation needed]
There aresemi-automatic pistols,rifles, andshotguns designed and made as semi-automatic only.Selective-fire firearms are capable of both full automatic and semi-automatic modes.
Semi-automatic refers to a firearm that uses the force of recoil or gas to eject the empty case and load a fresh cartridge into the firing chamber for the next shot and which allows repeat shots solely through the action of pulling the trigger. Adouble-action revolver also requires only a trigger pull for each round that is fired but is not considered semi-automatic since the manual action of pulling the trigger is what advances the cylinder, not the energy of the preceding shot.[4]
The usage of the termautomatic may vary according to context. Gun specialists point out that the wordautomatic is sometimes misunderstood to meanfully automatic fire 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. To avoid confusion, it is common to refer to such firearms as an "autoloader" in reference to their loading mechanism.
The term "automatic pistol" almost exclusively refers to a semi-automatic (i.e. not fully automatic) pistol (fully automatic pistols are usually referred to asmachine pistols). 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, to avoid confusion, the term "automatic rifle" is generally, conventionally, and best restricted to a rifle capable of fully automatic fire. Both uses of the term "automatic" can be found; the exact meaning must be determined from context.
The mechanism of semi-automatic (or autoloading) firearms is usually what is known as aclosed-bolt 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 andfiring pin move, striking and firing the cartridge. The bolt then recoils far enough rearward to extract and load a new cartridge from themagazine into the firearm's chamber, ready to fire again once the trigger is pulled.
Anopen-bolt 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 insubmachine guns 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, as thecentre of gravity changes relatively little at the moment the trigger is pulled.
With fully automatic weapons, the open-bolt operation allows air to circulate, cooling the barrel. With semi-automatic firearms, the closed-bolt operation is preferred, as overheating is not as critical, and accuracy is preferred. Some select-fire military weapons use an open bolt in fully automatic mode and a closed bolt when semi-automatic is selected.
Many jurisdictions regulate some or all semi-automatic firearms differently than other types.
Various types of semi-automatic weapons were restricted for civilian use in New Zealand after the 2019Christchurch mosque shootings, in Australia after the 1996Port Arthur massacre, in Norway after the 2011Utøya shooting.[5] In the United States, the 1994–2004Federal Assault Weapons Ban prohibited semi-automatic weapons with certain additional characteristics. As of 2023, severalU.S. states still restrict similar types of semi-automatic weapons.
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