Semi-automatic self-loading pistol

A semi-automatic pistol is a type of pistol that is semiautomatic, meaning it uses the energy of the fired cartridge to cycle the action of the firearm and advance the next available cartridge into position for firing. One cartridge is fired each time the trigger of a semi-automatic pistol is pulled; the pistol's "disconnector" ensures this behavior.

Additional terms sometimes used as synonyms for a semi-automatic pistol are automatic pistol, self-loading pistol, autopistol, and autoloading pistol.

A semi-automatic pistol harnesses the energy of one shot to reload the chamber for the next. After a round is fired, the spent casing is ejected and a new round from the magazine is loaded into the chamber, allowing another shot to be fired as soon as the trigger is pulled again. Most pistols use recoil operation to do this, but some pistols use blowback or gas operation.

Most types of semi-automatic pistols rely on a removable magazine to store ammunition before it is fired, usually inserted inside the grip.

Typically, the first round is manually loaded into the chamber by pulling back and releasing the slide mechanism. This is called racking the slide or racking the gun. After the trigger is pulled and the round is fired, the recoil operation of the handgun automatically extracts and ejects the shell casing and reloads the chamber. This mode of operation generally allows for faster reloading and storing a larger number of cartridges than a revolver.

Some modern semi-automatic pistols are double action only (DAO); that is, once a round is chambered, each trigger pull cocks the hammer, striker, or firing pin, and additionally releases the same to fire a cartridge in one continuous motion. Each pull of the trigger on a DAO semi-automatic pistol requires the same amount of pressure. The Kel-Tec P-32 is an example of a DAO action. DAO semi-automatic pistols are most generally recommended only in the smaller, self-defense, concealable pistols, rather than in target or hunting pistols. A notable exception is Glock-brand pistols which optimize preset triggers (similar to DAO), but the striker is partially cocked back as the slide closes. This allows for significantly shorter trigger pulls than DAO. The trigger spring can be replaced with a lighter one and paired with a low-strength sear connector resulting in lightened trigger pulls to improve a shooter's accuracy (like models G34 and G35).

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