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Semiautomatic and Automatic

Home > Propellants, Firearms, and Ammunition Development > Evolution of Firearms > Repeating Firearms > Semiautomatic and Automatic
Recoil Operated

Once repeating operation had been achieved, designers sought ways to automate the action; pulling the trigger should be all that is required. Designers knew that chemical energy was already available in the cartridge for faster operation of the firearm. Firearms recoil or kick due to classic physics: for every action there is an equal and opposite reaction. Recoil energy can be redirected to operate the firearm. Semiautomatic and full automatic fire are similar in operation; many semiautomatic designs can be adapted to full automatic capability by military arsenals.

The first inventor credited with using recoil to operate a gun action was Hiram Maxim. Between 1881 and 1883, he experimented with adding levers and springs to an existing Winchester lever-action rifle to harness recoil and cycle the action. He obtained a U.S. Patent in 1884 for a recoil-operated semiautomatic firearm. The design in Maxim’s patent was not for the Winchester conversion used in his experiments, but for a new design. It incorporated a fully locked breech suitable for high-power cartridges and used a long-recoil system.

For low-powered cartridges that reach peak firing pressure quickly, the bolt does not need to be locked for safe pressure control. The bolt mass and the bolt return spring are sufficient to hold the bolt closed briefly during firing. This is common in semiautomatic .22 caliber rimfire arms. Recoil and gas pressure push the bolt open, extract the spent cartridge, cock the firing mechanism, and chamber a fresh cartridge. This type of unlocked recoil-operated action is called blowback.

Some firearms require a locked breech to safely handle cartridges of greater power and longer peak pressure duration. Greater momentum is needed to unlock the bolt so the cycle can continue. This is accomplished by allowing some part of the firearm (usually the barrel) to move rearward with the cartridge. The extra mass of the added moving parts provides the additional momentum needed to unlock the action and provides a slight delay to allow cartridge pressures to fall before the action unlocks.

Depending on how far the parts move, the system is called short recoil or long recoil. When parts move less than 1/2 inch, the action is considered short-recoil (e.g., Colt Model 1911 and Luger Model 1908). When the movement of parts is nearly equal to the length of the cartridge, the term long recoil is applied (e.g., Remington Model 11 and Browning Model A5 shotguns).

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