The Probert Encyclopaedia of Warfare

FIRING PIN

A firing pin or striker is the part of a gun or rifle which detonates the cap in the cartridge. The firing pin is a pointed rod actuated by a strong spring, which, when the trigger is squeezed, forces the firing pin forward against the cartridge cap, thus causing detonation. In bolt-action rifles the firing pin and spring are contained in the bolt; when this is drawn back, pushed forward and turned down, the firing pin is automatically drawn back or cocked, ready for firing. In most shot guns and revolvers the firing pin is forced forward by a hammer which is drawn back against a spring to be cocked, and is released by the trigger.
Research Firing Pin