Hammer (firearms)

[3][4] In the development of firearms, the flintlock used flint striking steel to produce sparks and initiate firing by igniting the gunpowder used as a propellant.

Pulling the trigger allowed the cock to rotate forward at a speed sufficient to produce sparks when it struck the steel frizzen.

The cap was placed over an external nipple, which acts as an anvil and conduit to ignite the main propellant charge within the breech.

The caplock was in wide use for almost five decades until the widespread introduction of the self-contained cartridge which contained the projectile, gunpowder, and percussion cap all in a single shell that could be easily loaded from the breech of a firearm.

In single-action revolvers, specifically, there is an ever-present danger of accidentally discharging the weapon if the hammer is struck with a cartridge loaded in the chamber.

[8] There is nothing to prevent the hammer from contacting the firing pin and by default the cartridge, in some models, and so the gun will be discharged unintentionally.

Other models do have an internal safety mechanism that prevents contact between the hammer and the firing pin unless the trigger is actually pulled.

Paul B. Weston, an authority on police weapons, called the external a "fish hook" that tended to snag clothing during a fast draw.

From the top: striker-fired, linear hammer with free-floating firing pin, hammer-fired with free-floating firing pin, and hammer-fired with integral firing pin
Flintlock firing
All caplock mechanisms rely upon a hammer impact.
A Colt Single Action Army at half-cock , showing the external hammer and integral firing pin typical of many revolvers .
A Marlin Model 1894 rifle. The hammer and firing pin are separate components.
The M16 rifle uses an internal hammer.
An external hammer that could easily catch on clothing