The hammer is the mechanism that strikes the firing pin, which ignites the primer charge and the propellant and sends the bullet downrange. It is held in place by the sear.
In firearms, most hammers are pivoted. Another form is a linear hammer which is different as it works similar to a striker. A linear hammer differs to a striker as its found in the weapons receiver whereas a striker is basically a firing pin actuated by the trigger and found within the bolt.
Variations[]
In revolvers[]
In double-action revolvers, the hammer is automatically pulled back and released on the primer charge after the trigger is pulled.
In single-action revolvers, the hammer has to be pulled back manually to turn the cylinder.
In muskets[]
The only type of musket to have a hammer is a caplock: in these weapons, the hammer strikes the percussion cap of the weapon to detonate it. Older types of musket action use components which are similar in shape, but mechanically dissimilar and are not called hammers: a matchlock has a serpentine and a flintlock has a cock, both being a moving clamp to hold the match or flint, while a wheellock has a dog which holds the iron pyrite piece and "dogs" the motion of the wheel as it rotates.
In semi-automatic rifles and automatic rifles[]
The hammer is located inside the receiver and when released, strikes a firing pin that is inside the bolt carrier. The bolt carrier assembly then cycles back, cocking the hammer back in the process. In a semi-automatic rifle, the hammer is caught by a sear and not released until the trigger is pulled again. In an automatic weapon, the hammer is caught by an auto sear, which releases the hammer when the bolt carrier is completely forward and the bolt is in battery, firing the weapon as long as the trigger is held down.