Recoil operation

Recoil operation is an operating mechanism used to implement locked-breech, autoloading firearms. Recoil operated firearms use the energy of recoil to cycle the action.


  • 1 History
  • 2 Design
  • 3 Categories
    • 3.1 Long recoil
    • 3.2 Short recoil
    • 3.3 Inertia
      • 3.3.1 Muzzle booster
      • 3.3.2 Automatic revolvers
  • 4 Other autoloading systems
  • 5 See also
  • 6 References
  • 7 Bibliography
  • 8 External links


The earliest mention of recoil used to assist the loading of firearms is sometimes claimed to be in 1663 when an Englishman called Palmer proposed to employ either it or gases tapped along a barrel to do so. However no one has been able to verify this claim in recent times although there is another automatic gun that dates from the same year but its type and method of operation are unknown. Recoil-operation, if it was invented in 1663, would then lay dormant until the 19th century, when a number of inventors started to patent designs featuring recoil operation, this was due to the fact that the integrated disposable cartridge (both bullet and propellant in one easily interchangeable unit) made these designs viable. The earliest mention of recoil operation in the British patent literature is a patent by Joseph Whitworth filed in 1855 which proposed to use recoil to partially open the breech of a rifle, the breech then being manually pulled the rest of the way back by hand. Around this time an American by the name of Regulus Pilon is sometimes stated to have patented in Britain a gun that used a limited form of recoil operation though in fact there are three patents related to firearms by this man in the British patent literature around the 1850s to the 1860s all of them refer to a means of dampening recoil in firearms, which wasn't a new idea at the time, rather than true recoil operation. The next to mention recoil operation in the British patent literature is by Alexander Blakely in 1862, who clearly describes using the recoil of a fired cannon to open the breech. In 1864 in the aftermath of the Second Schleswig War Denmark started a program intended to develop a gun that used the recoil of a fired shot to reload the firearm though a working model wouldn't be produced until 1888. After Blakely and the Danish program came the patent by a Swedish captain called D. H. Friberg in the 1870s which introduced both flapper-locking and the fully automatic recoil operated machine gun. Furthermore, in 1875 a means of cocking a rifle through recoil was patented through the patent agent Frank Wirth by a German called Otto Emmerich. Finally came Maxim's 1883 automatic recoil operated machine gun which introduced the modern age of automatic machine guns.


The same forces that cause the ejecta of a firearm (the projectile(s), propellant gas, wad, sabot, etc.) to move down the barrel also cause all or a portion of the firearm to move in the opposite direction. The result is required by the conservation of momentum such that the ejecta momentum and recoiling momentum are equal. These momenta are calculated by:

Ejecta mass × ejecta velocity = recoiling mass × recoil velocity

In non-recoil-operated firearms, it is generally the entire firearm that recoils. However, in recoil-operated firearms, only a portion of the firearm recoils while inertia holds another portion motionless relative to a mass such as the ground, a ship's gun mount, or a human holding the firearm. The moving and the motionless masses are coupled by a spring that absorbs the recoil energy as it is compressed by the movement and then expands providing energy for the rest of the operating cycle.

Since there is a minimum momentum required to operate a recoil-operated firearm's action, the cartridge must generate sufficient recoil to provide that momentum. The... more

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