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Bolt (firearms)
A bolt is the part of a repeating, breechloading firearm that blocks the rear opening (breech) of the barrel chamber while the propellant burns, and moves back and forward to facilitate loading/unloading of cartridges from the magazine. The firing pin and extractor are often integral parts of the bolt. The terms "breechblock" and "bolt" are often used interchangeably or without a clear distinction, though usually, a bolt is a type of breechblock that has a nominally circular cross-section. In most automatic firearms that use delayed blowback, recoil or gas operation, the bolt itself is housed within the larger bolt carrier group (BCG), which contains additional parts that receives rearward push from a gas tube ( direct impingement) or a piston system. The slide of a self-loading pistol can be considered a bolt carrier, as it contains the same components and serves the same functions. Description In manually operated firearms such as bolt-action, lever-action, and pump-a ...
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Pistol Slide
The slide on the majority of fully/semi-automatic pistols is the upper part that reciprocates ("slides") with recoil during the gun's operating cycle. It serves as the bolt carrier group (BCG) and partly as the receiver, and generally houses the firing pin/ striker, the extractor and frequently also the barrel, and provides a mounting platform for iron and optical sights. Through the principles of short recoil or simple blowback operations, the slide is moved backwards with each shot by the energy of expanding gasses caused by the combusting propellant (often a nitrocellulose-based smokeless powder, very rarely black powder). Because the slide is spring-loaded, once at the rearmost position, the spring tension will push it back towards the front. Generally, this slide movement cycle serves three functions: the extractor will empty the chamber by pulling out the spent casing from the previous shot (which then gets removed out of the gun by the ejector), the slide inertia ...
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Rotating Bolt
Rotating bolt is a method of locking the breech (or rear barrel) of a firearm closed for firing. Johann Nicolaus von Dreyse developed the first rotating bolt firearm, the " Dreyse needle gun", in 1836. The Dreyse locked using the bolt handle rather than lugs on the bolt head like the Mauser M 98 or M16. The first rotating bolt rifle with two lugs on the bolt head was the Lebel Model 1886 rifle. The concept has been implemented on most firearms chambered for high powered cartridges since the 20th century. Design Ferdinand Ritter von Mannlicher, who had earlier developed a non-rotating bolt straight-pull rifle, developed the Steyr-Mannlicher M1895, a straight-pull rifle with a rotating bolt, which was issued to the Austro-Hungarian Army. Mannlicher then developed the M1893 auto rifle which had a screw delayed bolt and later the Mannlicher M1900 operated by a gas piston. This was an inspiration for later gas operated, semi-automatic and selective fire firearms (such as the ...
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Telescoping Bolt
A telescoping bolt (also known as an overhung bolt) is a firearm bolt which telescopes over, that is, wraps around and past, the breech end of the barrel. This feature reduces the required length of a weapon such as a submachine gun significantly, and it allows rifle designs to be balanced around the pistol grip in a way that gives "pointability" similar to a pistol's. While it would be simpler and easier to shorten the bolt to fit completely behind the breech, the bolt must have a certain amount of mass in order to operate reliably with a given caliber. The telescoping bolt moves some of that mass forward of the bolt face, resulting in a bolt which may be longer overall, but is shorter behind the bolt face. Though technically a different, distinct concept, nearly all telescoping bolt submachine guns use a magazine located in the pistol grip used to hold and fire the weapon. However, there are blowback firearms with the magazine located in the grip that do not use a telescopin ...
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Spring (device)
A spring is an elastic object that stores mechanical energy. In everyday use the term often refers to coil springs, but there are many different spring designs. Modern springs are typically manufactured from spring steel, although some non-metallic objects like the bow are also springs. When a conventional spring, without stiffness variability features, is compressed or stretched from its resting position, it exerts an opposing force approximately proportional to its change in length (this approximation breaks down for larger deflections). The ''rate'' or ''spring constant'' of a spring is the change in the force it exerts, divided by the change in deflection of the spring. That is, it is the gradient of the force versus deflection curve. An extension or compression spring's rate is expressed in units of force divided by distance, for example or N/m or lbf/in. A torsion spring is a spring that works by twisting; when it is twisted about its axis by an angle, it produc ...
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Gas Operation
Gas-operation is a system of operation used to provide energy to operate locked breech, autoloading firearms. In gas-operation, a portion of high-pressure gas from the cartridge being fired is used to power a mechanism to dispose of the spent case and insert a new cartridge into the chamber. Energy from the gas is harnessed through either a port in the barrel or a trap at the muzzle. This high-pressure gas impinges on a surface such as a piston head to provide motion for unlocking of the action, extraction of the spent case, ejection, cocking of the hammer or striker, chambering of a fresh cartridge, and locking of the action. History The first mention of using a gas piston in a single-shot breech-loading rifle comes from 1856, by the German Edward Lindner who patented his invention in the United States and Britain. In 1866, Englishman William Curtis filed the first patent on a gas-operated repeating rifle, but subsequently failed to develop that idea further. Between 1 ...
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Blowback (firearms)
Blowback is a system of operation for self-loading firearms that obtains energy from the motion of the cartridge case as it is pushed to the rear by expanding gas created by the ignition of the propellant charge. Several blowback systems exist within this broad principle of operation, each distinguished by the methods used to control bolt movement. In most actions that use blowback operation, the breech is not locked mechanically at the time of firing: the inertia of the bolt and recoil , relative to the weight of the bullet, delay opening of the breech until the bullet has left the barrel. A few locked breech designs use a form of blowback (example: primer actuation) to perform the unlocking function. The blowback principle may be considered a simplified form of gas operation, since the cartridge case behaves like a piston driven by the powder gases. Other operating principles for self-loading firearms include delayed blowback, blow forward, gas operation, and recoil operat ...
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Recoil
Recoil (often called knockback, kickback or simply kick) is the rearward thrust generated when a gun is being discharged. In technical terms, the recoil is a result of conservation of momentum, as according to Newton's third law the force required to accelerate something will evoke an equal but opposite reactional force, which means the forward momentum gained by the projectile and exhaust gases (ejectae) will be mathematically balanced out by an equal and opposite momentum exerted back upon the gun. In hand-held small arms, the recoil momentum will be eventually transferred to the ground, but will do so through the body of the shooter hence resulting in a noticeable impulse commonly referred to as a "kick". In heavier mounted guns, such as heavy machine guns or artillery pieces, recoil momentum is transferred to the Earth's surface through the platform on which the weapon is mounted. In order to bring the rearward moving gun to a halt, the momentum acquired by the gu ...
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Automatic Firearm
An automatic firearm is an auto-loading 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 ignite the propellant and discharge 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 magazine or a belt) remains available. In contrast, a firearm is considered " semi-automatic" if it only automatically cycles to chamber new rounds (i.e. 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 rou ...
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Semi-automatic Firearm
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 (self-loading) 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, allow it to "reset", before pulling the trigger again to fire off the next round. As a resul ...
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Self-loading Firearm
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 (self-loading) 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, allow it to "reset", before pulling the trigger again to fire off the next round. As a result, ...
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Pump-action
Pump action or slide action is a repeating firearm action that is operated manually by moving a sliding handguard on the gun's forestock. When shooting, the sliding forend is pulled rearward to eject any expended cartridge and typically to cock the hammer/ striker, and then pushed forward to load (''chamber'') a new cartridge into the chamber. Most pump-action firearms use an integral tubular magazine, although some do use detachable box magazines. Pump-action is typically associated with shotguns, although it has been used in rifles and other firearms as well. Because the forend is manipulated usually with the support hand, a pump-action gun 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 the trigger while reloading. Also because the action is cycled in a linear fashion, it creates less torque that can tilt and throw the gun off aim when repeat-firing rapidly. History The first slide acti ...
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