A trigger is a mechanical component designed to initiate an action, particularly in firearms. Its purpose is to release stored energy or activate a mechanism, transitioning a device from a ready to an active state. It serves as the primary interface between a user and the device’s operation.
Basic Mechanism of a Trigger
A trigger’s operation involves a precise sequence of mechanical events. When pressure is applied, the trigger moves, translating user input into internal mechanical action. This movement causes it to interact with the sear, which retains a hammer or striker under spring tension.
As the trigger moves rearward, it disengages the sear. This releases stored spring energy, allowing the hammer or striker to move forward rapidly. The hammer or striker then impacts a firing pin, striking the primer of a cartridge, igniting the propellant and launching the projectile.
Key Components of a Trigger System
A complete trigger mechanism consists of several interconnected parts. The trigger shoe is the part a user touches, typically a small, flat, or curved lever. The trigger bar connects to the shoe, transferring motion to other components.
In hammer-fired systems, a hammer pivots to strike a firing pin; in striker-fired systems, the striker acts as the firing pin.
Common Trigger Types
Trigger mechanisms are categorized by their operational characteristics. A single-action (SA) trigger releases a pre-cocked hammer or striker. For SA firearms, the hammer or striker must be manually cocked or cocked by the firearm’s cycling action before release. This design results in a lighter, shorter trigger pull, often preferred for precision shooting.
A double-action (DA) trigger performs two actions with a single pull: it cocks the hammer or striker, then releases it to fire. This dual function means DA triggers have a longer, heavier pull than SA triggers. Some firearms feature a double-action/single-action (DA/SA) system: the first shot is double-action, while subsequent shots are single-action as the firearm’s operation automatically recocks the hammer. Striker-fired systems, common in modern pistols, involve a partially cocked striker that the trigger fully cocks and then releases, providing a consistent pull.
Trigger Safety
Trigger mechanisms also play a role in safety. Many trigger systems incorporate safety features to prevent unintentional discharges. Some firearms utilize a manual safety, a separate lever or button that must be disengaged before the trigger functions.
Trigger safeties are integrated directly into the trigger, often appearing as a small lever that must be depressed along with the main trigger for it to move rearward. This design helps prevent firing if dropped or subjected to indirect pressure. Keeping one’s finger off the trigger until firing remains a foundational aspect of safe firearm handling, regardless of specific trigger safety features.