Trigger (firearms)

{

"text": "A trigger is a mechanism used to actuate a ranged weapon or device. This includes firearms, airguns, crossbows, and spearguns. The term also describes switches that initiate other tools, such as power tools or traps.

At its core, a trigger allows a small amount of energy to release a much larger amount of energy. While people often use the word to describe the visible trigger blade, it technically refers to the entire trigger group. This group contains all the internal parts that work together to start the firing process.\n\nTo understand how a firearm fires, we must look at the internal chain of events. The process begins when a user applies force to the trigger. This force moves the trigger to release a component called the sear. The sear is the interface that holds the hammer or striker under tension.

Once the sear is disengaged, the stored elastic energy in a mainspring is released. This energy is transmitted through an intermediate mechanism to a striking device. This device then hits the cartridge primer, which contains shock-sensitive compounds like lead styphnate. The resulting spark ignites the propellant powder, discharging the projectile.\n\nThere are two primary types of striking mechanisms used in this process. The first is a hammer, which is a pivoting metallic component. When released, it swings forward like a mallet hitting a chisel to strike a firing pin. The second type is a striker, which is essentially a firing pin loaded directly to a spring. A striker eliminates the need for a separate hammer because it moves forward along its own axis. Both methods rely on the sudden transfer of kinetic energy to ignite the cartridge.\n\nWhen a person pulls a trigger, they experience three distinct mechanical stages. The first stage is known as takeup, or pretravel. This is the movement of the trigger before the sear begins to move.

The second stage is the break. This occurs when the sear reaches its release point and the felt resistance suddenly decreases. The third stage is overtravel. This is the residual movement of the trigger after the sear has already released. Overtravel can be important for accuracy, especially in firearms with long barrels or heavy trigger weights.\n\nTriggers are often categorized by how they feel during these stages. Single-stage triggers, or direct triggers, have no discernible resistance during the takeup. They only encounter resistance at the very end, often called \"the wall.\" These are popular for hunting. Two-stage triggers, or pressure triggers, are common in competition rifles. These have a light resistance during takeup, followed by a much heavier resistance during the break. This allows a shooter to \"ease into\" the pull to maintain accuracy.\n\nThe amount of force required to overcome the sear during the break is called the trigger weight. This weight is measured using various units, such as newtons in SI units or pounds and ounces in US customary units. A slow, heavy trigger break is sometimes called a \"creep,\" which is often viewed as an unfavorable feature. Conversely, some shooters prefer a \"crisp\" break, which features a heavier weight and very little movement.

Controlling these forces is vital for preventing unwanted shakes at the instant of firing.\n\nTriggers are also classified by their \"action," or the number of functions they perform. A single-action (SA) trigger performs only one task: releasing the hammer or striker. In these systems, the user must cock the weapon through a separate action. This design was common in 19th-century revolvers like the Colt Model 1873 Single Action Army. In contrast, a double-action (DAO) trigger must both cock and release the hammer in one continuous motion. This requires more force because the trigger must perform two jobs for every single shot.\n\nModern firearms often use hybrid designs known as DA/SA. These pistols function in double-action mode for the first shot, allowing the weapon to be carried safely with a lowered hammer. After the first shot, the slide automatically recocks the hammer, and subsequent shots are fired in single-action mode. This evolution began in the late 1930s with models like the Walther P38. These systems combine the safety of a double-action start with the lighter pull of a single-action finish.",

"media": [

"File:Trigger mechanism bf 1923.jpg",

"File:Thompson submachine gun Firecontrols.jpg",

"File:MG 34 trigger RCR Museum noBG.jpg"

]

}