Through the principles of short recoil or simple blowback operations, the slide is moved backwards with each shot by the energy of expanding gasses caused by the combusting propellant (often a nitrocellulose-based smokeless powder, very rarely black powder). Because the slide is spring-loaded, once at the rearmost position, the spring tension will push it back towards the front. Generally, this slide movement cycle serves three functions: the extractor will empty the chamber by pulling out the spent casing from the previous shot (which then gets removed out of the gun by the ejector), the slide inertia will cock the hammer/striker to prepare for the next shot, and the bolt will push a new cartridge from the magazine into the chamber when the slide comes back forward. This action cycle will be repeated for continued firing as long as ammunitions are replete, and that there are no failure to extract/eject (which causes stovepiping and double-feeding), failure to feed or out-of-battery malfunctions occurring.
Fully/semi-automatic air pistols' slides operate with similar principles as firearms, except they utilize pneumatic energy from compressed gas (usually air, CO2, propane or refrigerants) instead of burning propellants. Because air pistols typically have much lower muzzle energy than firearms, there is less recoil that can be used to operate the slide. However, because airgun pellets/shots have no casings that needed to be extracted (unlike firearm cartridges), a very brief slide movement is sufficient to cycle the action and load the subsequent shot, so only a small amount of energy is needed to move the slide.
On most modern designs, once the magazine is empty, a slide stop will catch and lock the slide at its rearmost position, and will only be released to move back forward after the slide release is depressed.
Having the slide automatically loading the chamber and cocking the hammer/striker with each prior shot is essential for the function of double-action/single-action pistols. Hammerless and striker-fired pistols, lacking external hammer that can be directly manipulated, need to have the whole slide manually pulled back to cock the hammer/striker if the gun is not already cocked for firing.
Single-shot firearms are firearms that hold only a single round of ammunition, and must be reloaded manually after every shot. The history of firearms began with single-shot designs, then multi-barreled designs appeared, and eventually many centuries passed before multi-shot repeater designs became commonplace.
In firearms terminology, an action is the functional mechanism of a breech-loading firearm that handles the ammunition cartridges, or the method by which that mechanism works. Actions are technically not present on muzzleloaders, as all those are single-shot firearms with a closed off breech with the powder and projectile manually loaded from the muzzle. Instead, the muzzleloader ignition mechanism is referred to as the lock.
A semi-automatic firearm, also called a self-loading or autoloading firearm, is a repeating firearm whose action mechanism automatically loads a following round of cartridge into the chamber (self-loading) and prepares it for subsequent firing, but requires the shooter to manually actuate the trigger in order to discharge each shot. Typically, this involves the weapon's action utilizing the excess energy released during the preceding shot to unlock and move the bolt, extracting and ejecting the spent cartridge case from the chamber, re-cocking the firing mechanism, and loading a new cartridge into the firing chamber, all without input from the user. To fire again, however, the user must actively release the trigger, allow it to "reset", before pulling the trigger again to fire off the next round. As a result, each trigger-pull only discharges a single round from a semi-automatic weapon, as opposed to a fully automatic weapon, which will shoot continuously as long as the ammunition is replete and the trigger is kept depressed.
A semi-automatic pistol is a type of repeating single-chamber handgun (pistol) that automatically cycles its action to insert the subsequent cartridge into the chamber (self-loading), but requires manual actuation of the trigger to actually discharge the following shot. As a result, only one round of ammunition is fired each time the trigger is pulled, as the pistol's fire control group disconnects the trigger mechanism from the firing pin/striker until the trigger has been released and reset.
A repeating rifle is a single-barreled rifle capable of repeated discharges between each ammunition reloads. This is typically achieved by having multiple cartridges stored in a magazine and then fed individually into the chamber by a reciprocating bolt, via either a manual or automatic action mechanism, while the act of chambering the round typically also recocks the hammer/striker for the following shot. In common usage, the term "repeating rifle" most often refers specifically to manual repeating rifles, as opposed to self-loading rifles, which use the recoil and/or blowback of the previous shot to cycle the action and load the next round, even though all self-loading firearms are technically a subcategory of repeating firearms.
Pump action or slide action is a repeating firearm action that is operated manually by moving a sliding handguard on the gun's forestock. When shooting, the sliding forend is pulled rearward to eject any expended cartridge and typically to cock the hammer/striker, and then pushed forward to load (chamber) a new cartridge into the chamber. Most pump-action firearms use an integral tubular magazine, although some do use detachable box magazines. Pump-action is typically associated with shotguns, although it has been used in rifles and other firearms as well.
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.
A breechblock is the part of the firearm action that closes the breech of a breech loading weapon before or at the moment of firing. It seals the breech and contains the pressure generated by the ignited propellant. Retracting the breechblock allows the chamber to be loaded with a cartridge.
An automatic revolver also known as semi-automatic revolver, is a revolver that uses the energy of firing for cocking the hammer and revolving the cylinder, rather than using manual operations to perform these actions. Despite the name "automatic", such revolvers are actually semi-automatic as the gun will not continue shooting and the shooter still needs to manually actuate the trigger to discharge each shot.
Gas-operation is a system of operation used to provide energy to operate locked breech, autoloading firearms. In gas-operation, a portion of high-pressure gas from the cartridge being fired is used to power a mechanism to dispose of the spent case and insert a new cartridge into the chamber. Energy from the gas is harnessed through either a port in the barrel or a trap at the muzzle. This high-pressure gas impinges on a surface such as a piston head to provide motion for unlocking of the action, extraction of the spent case, ejection, cocking of the hammer or striker, chambering of a fresh cartridge, and locking of the action.
A bolt is the part of a repeating, breechloading firearm that blocks the rear opening (breech) of the barrel chamber while the propellant burns, and moves back and forward to facilitate loading/unloading of cartridges from the magazine. The firing pin and extractor are often integral parts of the bolt. The terms "breechblock" and "bolt" are often used interchangeably or without a clear distinction, though usually, a bolt is a type of breechblock that has a nominally circular cross-section.
In breechloading firearms, an extractor is an action component that serves to remove spent casings of previously fired cartridges from the chamber, in order to vacate the chamber for loading a fresh round of ammunition.
A trigger is a mechanism that actuates the function of a ranged weapon such as a firearm, airgun, crossbow, or speargun. The word may also be used to describe a switch that initiates the operation of other non-shooting devices such as a trap, a power tool or a quick release. A small amount of energy applied to the trigger leads to the release of much more energy.
Limp wristing is a phenomenon commonly encountered by semi-automatic pistol shooters, where the shooter's grip is not firm enough and the wrist is not held firm/straight enough to keep the frame of the firearm from traveling rearward while the bolt or slide of the pistol cycles. This condition often results in a failure to complete the operating cycle, properly termed a malfunction, but commonly termed a "jam". Rifles and shotguns, if fired without the stock in the shoulder, may also be prone to limp wristing. Of the important variables involved in this type of malfunction, bullet and gas momentum, slide and barrel mass, recoil spring pre-load and spring rate, and shooting hand and arm mass are much more important than the compliance (limpness) of the wrist.
A muzzle booster or recoil booster is a device fixed to the muzzle of a firearm, intended to harness the energy of the escaping propellant to augment the force of recoil on portions of the firearm. In spite of its name, a muzzle booster does not increase muzzle force or velocity but instead is usually used to improve the reliability and/or rate of fire of a recoil operated firearm.
The following are terms related to firearms and ammunition topics.
A firearm malfunction is the failure of a firearm to operate as intended for causes other than user error. Malfunctions range from temporary and relatively safe situations, such as a casing that did not eject, to potentially dangerous occurrences that may permanently damage the gun and cause injury or death. Improper handling of certain types of malfunctions can be very dangerous. Following gun safety rules can prevent firearm malfunctions, and limit the damage inflicted by them if they do occur. Proper cleaning and maintenance of a firearm play a big role in preventing malfunctions.
In firearms, a safety or safety catch is a mechanism used to help prevent the accidental discharge of a firearm, helping to ensure safer handling.
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.
A repeating firearm, or repeater, is any firearm that is capable of being fired repeatedly before having to manually reload new ammunition into the weapon.
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