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.
Trigger mechanism in a bolt action rifle: (A) trigger, (B) sear, (C) striker spring, (D) striker.
Thompson submachine gun trigger
The double-crescent trigger on the MG 34, which enabled select fire capability without using a selector switch. Pressing the upper segment of the trigger produced semi-automatic fire, while holding the lower segment of the trigger produced fully automatic fire.
A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and used by an individual. The term is legally defined further in different countries.
The Colt Single Action Army, a revolver chambered in .45 Colt
The Glock 19, a pistol chambered in 9×19mm Parabellum
The Mosin–Nagant, a rifle chambered in 7.62×54mmR
The M4 carbine, a carbine derivative of the M16 rifle, chambered in 5.56×45mm NATO
