A
semiA semi-automatic, or self-loading firearm is a gun that after being fired, ejects the empty round that has been fired, loads a new cartridge, and cocks itself...
or fully-automatic
firearmA firearm is a device which projects either single or multiple projectiles at high velocity through a controlled explosion. The firing is achieved by the gases produced through rapid, confined burning of a propellant. This process of rapid burning is technically known as deflagration...
which is said to fire from a
closed bolt is one where, when ready to fire, a round is in the
chamberIn firearms, the chamber is that portion of the barrel or firing cylinder in which the cartridge is inserted prior to being fired. Rifles and pistols generally have a single chamber in their barrels, while revolvers have multiple chambers in their cylinder and no chamber in their barrel.The act of...
and the
boltA bolt is a mechanical part of a firearm that blocks the rear of the chamber while the propellant burns.In manually-operated firearms, such as bolt-action, lever-action, and pump-action rifles and shotguns, the bolt is held fixed by its locking lugs during firing, forcing all the expanding gas...
and working parts are forward. When the trigger is pulled the
firing pinA firing pin or striker is part of the firing mechanism used in a firearm or explosive device e.g. an M14 landmine or bomb fuze. Firing pins may take many forms, though the types used in landmines, bombs, grenade fuzes or other single-use devices generally have a sharpened point...
or striker fires the round, the action is cycled by the energy of the shot sending the bolt to the rear which extracts and ejects the empty cartridge case, the bolt then goes forward feeding a fresh round from the
magazineA magazine is an ammunition storage and feeding device within or attached to a repeating firearm. Magazines may be integral to the firearm or removable . The magazine functions by moving the cartridges stored in the magazine into a position where they may be loaded into the chamber by the ...
into the chamber, ready for the next shot.
When
World War IWorld War I , also known as the First World War, the Great War, and the War to End All Wars, was a global military conflict which involved most of the world's great powers, assembled in two opposing alliances: the Triple Entente and the Triple Alliance...
era machine guns were being tried for use on aircraft, the
Lewis gunThe Lewis Gun is a World War I era light machine gun of American design that was perfected and most widely used by the forces of the British Empire. It was first used in combat in World War I, and continued in service with a number of armed forces all the way through to the end of the Korean War...
was found to not be usable with an
interrupter gearAn interrupter gear is a device used on military aircraft and warships in order to allow them to target opponents without damaging themselves....
for forward firing through the propeller, due to its firing cycle starting with an
open boltA semi or fully automatic firearm is said to fire from an open bolt if, when ready to fire, the bolt and working parts are held to the rear. When the trigger is pulled the bolt goes forward, feeding a round from the magazine into the chamber and firing it...
.
A
semiA semi-automatic, or self-loading firearm is a gun that after being fired, ejects the empty round that has been fired, loads a new cartridge, and cocks itself...
or fully-automatic
firearmA firearm is a device which projects either single or multiple projectiles at high velocity through a controlled explosion. The firing is achieved by the gases produced through rapid, confined burning of a propellant. This process of rapid burning is technically known as deflagration...
which is said to fire from a
closed bolt is one where, when ready to fire, a round is in the
chamberIn firearms, the chamber is that portion of the barrel or firing cylinder in which the cartridge is inserted prior to being fired. Rifles and pistols generally have a single chamber in their barrels, while revolvers have multiple chambers in their cylinder and no chamber in their barrel.The act of...
and the
boltA bolt is a mechanical part of a firearm that blocks the rear of the chamber while the propellant burns.In manually-operated firearms, such as bolt-action, lever-action, and pump-action rifles and shotguns, the bolt is held fixed by its locking lugs during firing, forcing all the expanding gas...
and working parts are forward. When the trigger is pulled the
firing pinA firing pin or striker is part of the firing mechanism used in a firearm or explosive device e.g. an M14 landmine or bomb fuze. Firing pins may take many forms, though the types used in landmines, bombs, grenade fuzes or other single-use devices generally have a sharpened point...
or striker fires the round, the action is cycled by the energy of the shot sending the bolt to the rear which extracts and ejects the empty cartridge case, the bolt then goes forward feeding a fresh round from the
magazineA magazine is an ammunition storage and feeding device within or attached to a repeating firearm. Magazines may be integral to the firearm or removable . The magazine functions by moving the cartridges stored in the magazine into a position where they may be loaded into the chamber by the ...
into the chamber, ready for the next shot.
When
World War IWorld War I , also known as the First World War, the Great War, and the War to End All Wars, was a global military conflict which involved most of the world's great powers, assembled in two opposing alliances: the Triple Entente and the Triple Alliance...
era machine guns were being tried for use on aircraft, the
Lewis gunThe Lewis Gun is a World War I era light machine gun of American design that was perfected and most widely used by the forces of the British Empire. It was first used in combat in World War I, and continued in service with a number of armed forces all the way through to the end of the Korean War...
was found to not be usable with an
interrupter gearAn interrupter gear is a device used on military aircraft and warships in order to allow them to target opponents without damaging themselves....
for forward firing through the propeller, due to its firing cycle starting with an
open boltA semi or fully automatic firearm is said to fire from an open bolt if, when ready to fire, the bolt and working parts are held to the rear. When the trigger is pulled the bolt goes forward, feeding a round from the magazine into the chamber and firing it...
. The Maxim style arms used by both the
AlliesThe Triple Entente was the name given to the loose alignment between the United Kingdom, France, and Russia after the signing of the Anglo-Russian Entente in 1907...
, as the
Vickers machine gunThe Vickers machine gun or Vickers gun is a name primarily used to refer to the water-cooled .303 inch machine gun produced by Vickers Limited, originally for the British Army. The machine gun typically required a six- to eight-man team to operate: one to fire, one to feed the ammunition, and the...
and
Central PowersThe Central Powers was one of the two sides that participated in World War I, the other being the Entente Powers.-Member states:...
, as both the
LMG 08 and
LMG 08/15 Spandau gunThe Maschinengewehr 08, or MG08, was the German Army's standard machine gun in World War I and is an almost direct copy of Hiram S. Maxim's original 1884 Maxim Gun. It was produced in a number of variants during the war. The MG 08 remained in service until the outbreak of World War II due to a...
, and
Parabellum LMG 14 gun, all fired with a cycle starting with a closed bolt, and since the bullet firing from the gun started the firing cycle, it was much easier to set the interrupter to only trigger the gun when the propeller's blade was not in front of the gun.
Pros
- More accurate for the first round and for semi automatic fire:
- No movement of working parts to inhibit accuracy.
- Round sits consistently in the chamber.
- The action remaining closed the majority of the time prevents foreign debris from entering the gun.
- Potentially shorter delay between operator pulling the trigger and round being fired (also known as lock time).
- Action can be locked forward to further reduce noise in a suppressed
A suppressor, sound suppressor, sound moderator, or silencer, is a device either attached to or part of the barrel of a firearm to reduce the amount of noise and flash generated by firing the weapon...
weapon.
- Can carry an additional round in the chamber, increasing ammunition capacity beyond the magazine
A magazine is an ammunition storage and feeding device within or attached to a repeating firearm. Magazines may be integral to the firearm or removable . The magazine functions by moving the cartridges stored in the magazine into a position where they may be loaded into the chamber by the ...
's limit.
Cons
- More complicated and expensive to manufacture.
- Less heat dissipation
In physics, dissipation embodies the concept of a dynamical system where important mechanical modes, such as waves or oscillations, lose energy over time, typically due to the action of friction or turbulence. The lost energy is converted into heat, raising the temperature of the system...
from closed chamber. (Increased danger of cooking offCooking off refers to ammunition exploding prematurely due to heat in the surrounding environment. It can also refer to a technique used when throwing grenades to achieve a controlled, predictable explosion.-Artillery:...
)