page_title: Blowback (firearms)
section_title: Lever-delayed
hierarchical_section_title: Blowback (firearms) / Delayed blowback / Lever-delayed
caption_attribution_description: English: A schematic of the FAMAS rifle's Lever delayed blowback system.
context_page_description: 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 spring, 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 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 blow forward, gas operation, and recoil operation.
context_section_description: Lever-delayed blowback utilizes leverage to put the bolt at a mechanical disadvantage, delaying the opening of the breech. When the cartridge pushes against the bolt face, the lever moves the bolt carrier rearward at an accelerated rate relative to the light bolt. Leverage can be applied with a dedicated part or through inclined surfaces interacting with each other. This leverage significantly increases resistance and slows the movement of the lightweight bolt.  The reliable functioning of lever-delayed blowback arms is limited by specific ammunition and arm parameters like bullet weight, propellant charge, barrel length and amount of wear. John Pedersen patented the first known design for a lever-delay system. The mechanism was adapted by Hungarian arms designer Pál Király in the 1930s and used in the Danuvia 39M and 43M submachine guns for the Hungarian Army. After the World War II, Király settled in the Dominican Republic and developed the Cristóbal Carbine  (or Király-Cristóbal Carbine). Other weapons to use this system are the Hogue Avenger and Benelli B76 pistols, the FNAB-43 submachine gun, the TKB-517, VAHAN and FAMAS assault rifles, the Sterling 7.62 and AVB-7.62 battle rifles/light machine guns, and the AA-52 general-purpose machine gun.
caption: A schematic of the lever-delayed blowback mechanism used in the FAMAS assault rifle.
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