Autoloading - Semiautomatic Pistols
Semiautomatic pistols are typically magazine-fed repeating firearms that require a separate pull of the trigger to fire each shot. The energy of discharge performs some of the firing cycle functions such as extraction, ejection, cocking, and loading.
These pistols are magazine fed; a box type magazine is loaded with cartridges and placed into the magazine well, which is usually located in the pistol grip. Magazines are generally single or double stacked. The double-stacked type can hold a larger number of cartridges.
With the magazine in place, the slide is pulled to the rear and released.
- cocks the firearm,
- strips a cartridge from the magazine,
- inserts the cartridge into the chamber,
- locks the breech.
Most semiautomatic pistols have one of three major actions:
There are other variations of these basic semiautomatic systems, such as retarded or delayed blowback. This module covers the three major actions.
The blowback system is comprised of an unlocked breech that relies on the mass (weight) of the breechblock and the strength of the return spring to prevent the breech from opening and the cartridge case from being exposed during its period of peak pressure.
Low-pressure cartridges are generally used in blowback action pistols; however, there are several pistols that use high-pressure cartridges. These pistol systems tend to be heavier because the slide must be large enough to hold the firearm in battery until peak pressure is reduced. An internal striker or an external hammer is typically present. A visual check should determine the type of firing mechanism.
The recoil action is a locked breech system that relies on the recoil of the firearm at discharge to unlock the breech. The time required for the breech to unlock allows for the reduction of peak pressure within the chamber. High-pressure cartridges are generally used in recoil-action pistols. An internal striker or an external hammer is typically present. A visual check should determine the type of firing mechanism.
The gas-operated system is a locked breech system in which gas is bled from the barrel to move a piston rearward, unlocking the breech and cycling the firearm. The gas port is located near the muzzle and peak pressure is reduced before the gas is bled off. High-pressure cartridges are generally used in gas-operated action pistols. An external hammer is typically present.
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