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. In military use, the semi-automatic M1911 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 to World War II, the M1 Garand being a notable example. Modern service rifles such as the M4 carbine are often selective-fire, capable of semi-automatic and automatic or burst-fire operation. Civilian variants such as the AR-15 are generally semi-automatic only.
Early history (1885–1945)
The first successful design for a semi-automatic rifle is attributed to Austria-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 M1894, which employed an unusual blow-forward action and held five rounds of 6.5mm ammunition that were fed into the M1894 by a stripper clip.
Semi-automatic shotgun
In 1902, American gunsmith John Moses Browning developed the first successful semi-automatic shotgun, the Browning Auto-5, which was first manufactured by Fabrique Nationale de Herstal and sold in America under the Browning name. The Auto-5 relied on long recoil operation; this design remained the dominant form in semi-automatic shotguns for approximately 50 years. Production of the Auto-5 ended in 1998.
Blowback semi-automatic In 1903 and 1905, the Winchester Repeating Arms Company introduced the first semi-automatic rimfire and centerfire rifles designed especially for the civilian market. The Winchester Model 1903 and Winchester Model 1905 operated on the principle of blowback in order to function semi-automatically. Designed entirely by T. 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, including Winchester, Remington, Fabrique Nationale and Savage Arms, 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 blowback system of operation, in calibers such as .351 Winchester. Both the Models of 1905 and 1907 saw limited military and police use.
Notable early semi-automatic rifles In 1906, Remington Arms introduced the Remington 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 by John 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 the Fusil Automatique Modele 1917. This is a locked-breech, gas-operated action that is very similar in its mechanical principles to the future M1 Garand in the United States. The M1917 was fielded during the latter stages of World 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 Moroccan Rif War from 1920 to 1926. The Lebel bolt-action rifle remained the standard French infantry rifle until replaced in 1936 by the MAS-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 the United Kingdom, which had intended to replace the bolt-action Lee–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. The Soviet Union and Nazi 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.
Notable gas-operated rifles
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