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A bolt is the part of a repeating,
breechloading A breechloader is a firearm A firearm is any type of gun A gun is a ranged weapon designed to use a shooting tube ( gun barrel) to launch typically solid projectiles, but can also project pressurized liquid (e.g. water guns/ cannon ...
firearm A firearm is any type of gun A gun is a ranged weapon designed to use a shooting tube ( gun barrel) to launch typically solid projectiles, but can also project pressurized liquid (e.g. water guns/ cannons, spray guns for painting ...
that blocks the rear opening (breech) of the
barrel A barrel or cask is a hollow cylindrical A cylinder (from ) has traditionally been a Solid geometry, three-dimensional solid, one of the most basic of curvilinear geometric shapes. Geometrically, it can be considered as a Prism (geometry) ...
chamber while the
propellant A propellant (or propellent) is a mass Mass is the quantity Quantity is a property that can exist as a multitude or magnitude, which illustrate discontinuity and continuity. Quantities can be compared in terms of "more", "less", or " ...
burns, and moves back and forward to facilitate loading/unloading of
cartridge Cartridge may refer to: Media * Broadcast cartridge, used in radio stations * 8-track tape cartridge, a 1960s-1980s music storage format * Compact Cassette, used with sound recording and reproduction and data storage for early microcomputers * ...
s from the
magazine A magazine is a periodical publication Periodical literature (also called a periodical publication or simply a periodical) is a category of serial Serial may refer to: Arts, entertainment, and media The presentation of works in sequential ...
. The
firing pin #REDIRECT Firing pin #REDIRECT Firing pin , showing the integral firing pin A firing pin or striker is part of the firing mechanism used in a firearm or explosive device, designed to ignite combustions/detonations by delivering an impact (mechani ...
and extractor are often integral parts of the bolt. In most automatic firearms that use
delayed blowback Blowback is a system of operation for self-loading firearm A firearm is any type of gun A gun is a ranged weapon designed to use a shooting tube ( gun barrel) to launch typically solid projectiles, but can also project pressurized li ...
,
recoil Recoil (often called knockback, kickback or simply kick) is the rearward thrust Thrust is a described quantitatively by . When a system expels or in one direction, the accelerated mass will cause a force of equal but opposite directi ...
or
gas operation Gas-operation is a system of operation used to provide energy to operate locked breech Locked breech is the design of a breech-reloading firearm's action (firearms), action. This is important in understanding how a self-reloading firearm work ...
, 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 Direct impingement is a type of gas operation Gas-operation is a system of operation used to provide energy to operate locked breech, autoloading firearm A firearm is any type of gun designed to be readily carried and used by an individ ...
) or a
piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, Hydraulic cylinder, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder ...

piston
system. The
slide Slide or Slides may refer to: Places *Slide, California Fortuna (formerly, Slide, Springville) (Wiyot language, Wiyot: ''Vutsuwitk Da'l'', "ashes stay") is a city on the northeast shore of the Eel River (California), Eel River (approximately fr ...
of a
self-loading pistol A semi-automatic pistol is a type of repeating firearm, repeating single-chamber (firearms), chamber handgun (pistol) that automatically cycles its action (firearm), action to insert the subsequent cartridge (firearms), cartridge into the ch ...
can be considered a bolt, as it contains the same components and serves the same functions.


Description

In
manually operated
manually operated
firearms such as
bolt-action Bolt action is a type of manual firearm action of a typical double-barreled shotgun, with the action open and the extractor visible. The opening lever and the safety catch can also be clearly seen. In firearms A firearm is any type of gu ...
,
lever-action The toggle-link action used in the iconic Winchester Model 1873 rifle, one of the most famous lever-action firearms Lever action is a type of action ACTION is a bus operator in , Australia owned by the . History On 19 July 1926, the ...
, and
pump-action Pump action or slide action is a repeating firearm A repeating firearm, or repeater, is any firearm (either a handgun or long gun) that is capable of being fired repeatedly before having to manually reload new ammunition into the weapon. Un ...
rifles and shotguns, the bolt is held fixed by its locking lugs during firing, forcing all the expanding gas forward, and is manually unlocked and moved to extract the spent casing and chamber another round. In a
self-loading firearm A semi-automatic firearm A firearm is any type of gun A gun is a ranged weapon designed to use a shooting tube ( gun barrel) to launch typically solid projectiles, but can also project pressurized liquid (e.g. water guns/ cannons, ...
(
fully Fully is a Municipalities of Switzerland, municipality in the district of Martigny (district), Martigny in the Cantons of Switzerland, canton of Valais in Switzerland. History Fully is first mentioned in the 11th Century as ''Fuliacum''. Geograph ...
or semi-automatic), the bolt cycles back and forward between each shot, propelled back by
recoil Recoil (often called knockback, kickback or simply kick) is the rearward thrust Thrust is a described quantitatively by . When a system expels or in one direction, the accelerated mass will cause a force of equal but opposite directi ...

recoil
(
recoil operation Recoil operation is an operating mechanism used to implement locked breech Locked breech is the design of a breech-reloading firearm's action (firearms), action. This is important in understanding how a self-reloading firearm works. In the simple ...
) or the expanding gas ( blowback and
gas operation Gas-operation is a system of operation used to provide energy to operate locked breech Locked breech is the design of a breech-reloading firearm's action (firearms), action. This is important in understanding how a self-reloading firearm work ...
) and forward by a
spring Spring(s) may refer to: Common uses * Spring (season) Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of th ...
. When it moves back, the extractor pulls the spent casing of the previous shot from the chamber, and once the case is clear out of the chamber, the ejector kicks the case out of the firearm. When the bolt moves forward, it picks up a new cartridge from the
magazine A magazine is a periodical publication Periodical literature (also called a periodical publication or simply a periodical) is a category of serial Serial may refer to: Arts, entertainment, and media The presentation of works in sequential ...
and pushes it into the chamber. A telescoping bolt is a bolt that wraps around the breech end of the barrel. This bolt design is often used to reduce overall weapon length without sacrificing barrel length or bolt weight. A turn bolt refers to a firearm component that where the whole bolt without using a bolt carrier turns to lock/unlock. This is mostly used to describe manually operated bolt action firearms, but also on some automatic firearms. The most common locking mechanism on rifles is a
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 The Dreyse needle-gun was a ground-breaking 19th- ...

rotating bolt
, which can be classified as a rigid type of bolt lock. Semi-rigid bolt locks have their locking elements movably mounted on either the bolt, barrel or breech housing and using a bolt carrier. Examples of semi-rigid bolt locks are
roller-locked In firearms operating systems, the term roller locked refers to locking the bolt with rollers. Notable examples of firearms using this method are the MG 42 The MG 42 (shortened from German: ''Maschinengewehr 42'', or "machine gun 42") is a 7.92 ...
bolts, or ball bearings as on
Heym SR 30 The Heym SR 30 is a straight-pull rifle produced in Germany Germany (german: Deutschland, ), officially the Federal Republic of Germany, is a country in . It is the in Europe after , and the most populous . Germany is situated between the ...
or
Anschütz 1827 Fortner Anschütz 1827 Fortner is a straight-pull Bolt action is a type of manual firearm action of a typical double-barreled shotgun, with the action open and the extractor visible. The opening lever and the safety catch can also be clearly seen. ...
(both
straight-pull rifles Bolt action is a type of manual firearm action that is operated by directly manipulating the bolt (firearms), bolt via a cocking handle, bolt handle, which is most commonly placed on the right-hand side of the weapon (as most users are right-ha ...
).


Closed bolt vs. open bolt

In a closed bolt firearm, the bolt is in its foremost position upon firing. This is opposed to an open bolt firearm where the bolt is held rearward and pulling the trigger releases it to slam forward and fire the cartridge.


Gallery

File:Rugersrcarrier.jpg,
AR-15 An AR-15 style rifle is a lightweight semi-automatic rifle A semi-automatic rifle is a rifle that fires one Cartridge (firearms), round each pull of the Trigger (firearms), trigger. For comparison, a bolt-action rifle requires the user to c ...

AR-15
bolt carriers File:AK74 bolt.jpg,
AK-74 The AK-74 (Russian Russian refers to anything related to Russia, including: *Russians (русские, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (россияне ...
bolt and firing pin. File:K31 culasse open.jpg,
K31 The Karabiner Modell 1931 (K. 31/Kar. 31/Mq. 31) is a magazine A magazine is a periodical publication Periodical literature (also called a periodical publication or simply a periodical) is a category of serial Serial may refer to: Arts, ...
bolt disassembled File:Stgw, Verschluss, Feder.JPG, Automatic rifle bolt (top) from a
SIG SG 510 The SIG SG 510 or Sturmgewehr 57 is a selective fire battle rifle designed by Schweizerische Industrie Gesellschaft (now Swiss Arms, SAN Swiss Arms) of Switzerland. It uses a Blowback (arms)#Roller delayed, roller-delayed blowback system similar t ...
battle rifle File:MWSS-274 Marines qualify with heavy weapons 130520-M-OT671-037.jpg,
U.S. Marine The United States Marine Corps (USMC), also referred to as the United States Marines, is the Marines, maritime land force military branch, service branch of the United States Armed Forces responsible for conducting expeditionary warfare, expedi ...
s assemble the bolt group of the
Browning M2 The M2 machine gun or Browning .50 caliber machine gun is a heavy machine gun A heavy machine gun or HMG is a ammunition belt, belt-fed machine gun that fires full-powered rifle cartridge, full-powered/magnum cartridges and is designed to be ...

Browning M2
File:Desert Eagle beside a box of Speer 325 Grain HP.jpg, Slide locked back on a
Desert Eagle The Desert Eagle (colloquially, sometimes Deagle) is a Gas-operated reloading, gas-operated, semi-automatic pistol known for chambering the .50 Action Express, the largest centerfire cartridge of any magazine-fed, self-loading pistol. Magnum Res ...
pistol, showing the gas-operated rotating bolt mechanism


See also

*
Breechblock A breechblock (or breech block) is the part of the firearm action of a typical double-barreled shotgun, with the action open and the extractor visible. The opening lever and the safety catch can also be clearly seen. In firearms A firearm is ...
*
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 The Dreyse needle-gun was a ground-breaking 19th- ...

Rotating bolt
*
Telescoping bolt A telescoping bolt (also known as an overhung bolt) is a firearm bolt Bolt or bolts may refer to: Implements and technology * Bolt (fastener) A bolt is a form of threaded fastener with an external male thread requiring a matching pre-formed f ...
*
Action (firearms) In firearms A firearm is any type of gun A gun is a designed to use a shooting tube () to launch typically solid s, but can also project pressurized (e.g. s/s, s for or , , and technically also s), (e.g. ) or even s (e.g. ). Sol ...


References


Full Auto
describes the function of the bolt in detail Firearm components {{firearms-stub bg:Затвор (оръжие) fr:Culasse (arme) it:Otturatore (armi) ru:Затвор (деталь оружия)