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A trigger is a mechanism that actuates the firing of a weapon. Firearms, spear guns and crossbows generally have a finger operated trigger.
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[编辑] 功用
Firearms utilize triggers to initiate the firing of a cartridge in the firing chamber of the weapon. This is accomplished by actuating a striking device through a combination of spring and kinetic energy operating through a firing pin to strike and ignite the primer. There are two primary types of striking mechanisms, hammers and strikers. Hammers are spring-tensioned masses of metal that pivot on a pin when released and strike a firing pin to discharge a cartridge. Strikers are, essentially, spring-loaded firing pins that travel on an axis in-line with the cartridge eliminating the need for a separate hammer. The connection between the trigger and the hammer is generally referred to as the sear surface. Variable mechanisms will have this surface directly on the trigger and hammer or have separate sears or other connecting parts.
[编辑] 機制
There are numerous types of trigger mechanisms. They are categorized according to which functions the trigger is to perform. In addition to releasing the hammer or the striker, a trigger may cock the hammer or striker, rotate a revolver's cylinder, deactivate passive safeties, select between semi-automatic and full-automatic fire (Steyr AUG), or pre-set a 'set trigger.' Most modern firearms utilize the trigger to deactivate passive safeties but this does not change how they are identified.
[编辑] Single action (SA)
A single-action trigger performs the single action of releasing the hammer or striker. Examples of the SA trigger operated firearms are the Colt Peacemaker revolver and Mauser 98 rifle. Single-action semi-automatic pistols require that the hammer be cocked before the first round is fired. Once the first round is fired the automatic movement of the slide cocks the hammer for each subsequent shot. The pistol, once cocked, can be fired by pulling the trigger once for each shot until the magazine is empty. The M1911 is a single-action pistol that functions in this manner.
[编辑] Single set trigger
A Set Trigger allows a shooter to have a greatly reduced trigger pull weight while maintaining a degree of safety in the field. There are two types: Single Set and Double Set. A Single Set Trigger is usually one trigger that may be fired with a conventional amount of trigger pull weight or may be 'set' by usually pushing forward on the trigger. This takes up the creep in the trigger and allows the shooter to enjoy a much lighter trigger pull.
[编辑] Double set trigger
As above, a double set trigger accomplishes the same thing, but uses two triggers: one sets the trigger and the other fires the weapon. Set triggers are most likely to be seen on customized weapons and competition rifles where a light trigger pull is beneficial to accuracy.
[编辑] Double action (DA)
Invented by Robert Adams, a double-action trigger performs the two functions of cocking and then releasing the hammer or striker. When this term is applied to revolvers, the trigger also rotates the cylinder. Though this is technically a third action, it is correct to refer to the mechanism as double-action. More confusingly, revolvers with a double-action trigger mechanism almost always retain the single action functionality. The hammer may be cocked and the trigger pulled. A typical DA revolver is the Smith and Wesson model 19 revolver.
[编辑] Double action only (DAO)
Double action only is similar to a DA revolver trigger mechanism however there is no single action function. For semi-automatic pistols with a traditional hammer, the hammer will return to its decocked position after each shot. For striker-fired pistols such as the Taurus 24/7, the striker will remain in the rest position through the entire reloading c
