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Semi-automatic rifle
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A semi-automatic rifle is a type of rifle that fires a single bullet each time the trigger is pulled. They may be operated by a number of mechanisms, all of which derive their power from the explosion of the powder in the cartridge that also fires the bullet.
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Encyclopedia
A semi-automatic rifle is a type of rifle that fires a single bullet each time the trigger is pulled. They may be operated by a number of mechanisms, all of which derive their power from the explosion of the powder in the cartridge that also fires the bullet. Historically, the self-loading design was the successor to the repeating rifle, which stored a number of cartridges within the weapon, but required manual action to load a fresh cartridge before each shot. Automatically loading the next round more easily allows for rapid fire. These rifles are also commonly known as self-loading rifles ('SLR') or auto-loading rifles.
A semi-automatic rifle is distinguished from a fully automatic rifle or machine gun in that it can only fire once each time the trigger is pulled. In some contexts, the term "automatic rifle" may refer to a semi-automatic/SLR rifle, not a fully automatic rifle.
Military-style semiautomatic rifle
Many semi-automatic-only versions (also known as "sporting" or "civilian" versions) of fully automatic assault rifles are available, and their external appearance can be nearly identical to their automatic counterparts. However, modern semi-automatic rifles are designed so that they cannot be converted easily to fully automatic fire. In the U.S., BATF regulations require that semi-automatic rifles be manufactured so that they cannot accept parts or modifications that would allow them to be capable of fully automatic fire.
Controversy
While some people believe military-style semiautomatic rifles are commonly used by criminals, a 2001 Justice Department study revealed that fewer than 2% of State and Federal inmates used, carried, or possessed a military-style semiautomatic gun or a fully automatic gun during their current offense . Semi-automatic rifles are mistakenly believed by many people to be capable of fully automatic fire or easily convertible to have that functionality. These perceptions have attracted the attention of gun control advocates, who have introduced and passed legislation restricting the sale, importation, ownership, and manufacture of semi-automatic rifles. In the United States, semi-automatic rifles with a military-style appearance were prohibited from manufacture or importation by the Federal Assault Weapons Ban, which was enacted in 1994 and expired in 2004. Certain U.S. states such as California, Massachusetts, New Jersey and New York have restrictive laws regarding to the ownership and sale of semi-automatic rifles.
Mechanisms
Blowback
In "blowback" operation, the bolt is not actually locked at the moment of firing. To prevent violent recoil, in most firearms using this mechanism the opening of the bolt is delayed in some way. In many small arms, the round is fired while the bolt is still travelling forward, and the bolt does not open until this forward momentum is overcome. Other methods involve delaying the opening until two rollers have been forced back into recesses in the receiver in which the bolt is carried.
Gas operated
In a gas-operated mechanism, a portion of the gases propelling the bullet from the barrel are extracted and used to operate a piston. The motion of this piston in turn unlocks and operates the bolt, which performs extraction of the spent cartridge and via spring action readies the next round. Almost all modern military rifles use mechanisms of this type.
Recoil operated
In some small caliber weapons, the bolt is not restrained but is relatively heavy and held against the breech by a spring. The gas pressure in the cartridge and the weapon recoil acts to push the bolt back, but owing to inertia this action does not significantly cause loss of gas pressure until after the bullet has left the barrel. Subsequent action is similar to that of the gas operated mechanism. This type of action is simple and inexpensive to manufacture, but is limited in the power it can handle, so it is seen on small caliber weapons such as machine pistols and submachine guns.
Types of semi-automatic rifles, by country and/or designer
Commercial semi-automatic rifles
Military semi-automatic rifles (and commercial derivatives)
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