Some info"
Set trigger[edit]
A set trigger allows a shooter to have a greatly reduced trigger pull (the resistance of the trigger) while maintaining a degree of safety in the field compared to having a conventional, very light trigger. There are two types: single set and double set. Set triggers are most likely to be seen on customized weapons and competition rifles where a light trigger pull is beneficial to accuracy.
Single set trigger[edit]
A single set trigger is usually one trigger that may be fired with a conventional amount of trigger pull weight or may be "set" – usually by pushing forward on the trigger, or by pushing forward on a small lever attached to the rear of the trigger. This takes up the trigger slack (or "take-up") in the trigger and allows for a much lighter trigger pull. This is colloquially known as a
hair trigger.
Double set trigger[edit]
A double set trigger achieves the same result, but uses two triggers: one sets the trigger and the other fires the weapon. Double set triggers can be further classified by phase.
[6] A double set, single phase trigger can only be operated by first pulling the set trigger, and then pulling the firing trigger. A double set, double phase trigger can be operated as a standard trigger if the set trigger is not pulled, or as a set trigger by first pulling the set trigger. Double set, double phase triggers offer the versatility of both a standard trigger and a set trigger.
Pre-set (striker or hammer)[edit]
Pre-set strikers and hammers apply only to semi-automatic handguns. Upon firing a cartridge or loading the chamber, the hammer or striker will rest in a partially cocked position. The trigger serves the function of completing the cocking cycle and then releasing the striker or hammer. While technically two actions, it differs from a double-action trigger in that the trigger is not capable of fully cocking the striker or hammer. It differs from single-action in that if the striker or hammer were to release, it would generally not be capable of igniting the primer. Examples of pre-set strikers are the
Glock,
Smith & Wesson M&P,
Springfield Armory XD-S variant (only),
Kahr Arms,
FN FNS series and
Ruger SR series pistols. This type of trigger mechanism is sometimes referred to as a Striker Fired Action or SFA. Examples of pre-set hammers are the
Kel-Tec P-32 and
Ruger LCP pistols.
Pre-set hybrid[edit]
Pre-set hybrid triggers are similar to a DA/SA trigger in reverse. The first pull of the trigger is pre-set. If the striker or hammer fail to discharge the cartridge, the trigger may be pulled again and will operate as a double-action only (DAO) until the cartridge discharges or the
malfunction is cleared. This allows the operator to attempt a second time to fire a cartridge after a misfire malfunction, as opposed to a single-action, in which the only thing to do if a round fails to fire is to rack the slide, clearing the round and recocking the hammer. While this can be advantageous in that many rounds will fire on being struck a second time, and it is faster to pull the trigger a second time than to cycle the action, if the round fails to fire on the second strike, the user will be forced to clear the round anyway, thus using up even more time than if they had simply done so in the first place. The
Taurus PT 24/7 Pro pistol (not to be confused with the first-generation
