Thehammer is a part of a firearm that is used to strike thepercussion cap/primer, or a separatefiring pin,[1] to ignite thepropellant and fire the projectile. It is so called because it resembles ahammer in both form and function. The hammer itself is a metal piece that forcefully rotates about a pivot point.[2]
The termtumbler can refer to a part of the hammer or a part mechanically attached to the pivot-point of the hammer, depending on the particular firearm under discussion (seehalf-cock). According to one source the term tumbler is synonymous with hammer.[3][4]
In the development of firearms, theflintlock usedflint striking steel to produce sparks and initiate firing by igniting thegunpowder used as a propellant. The flint was fixed to a swinging arm called thecock. Prior to firing, the cock was held rearward under spring tension. Pulling thetrigger allowed the cock to rotate forward at a speed sufficient to produce sparks when it struck the steelfrizzen. This ignited a small priming charge in the externalflash pan, which in turn ignited the propellent charge in thebreech through a connecting vent hole. The identification of percussion sensitivefulminates provided an alternative to spark ignition of the propellant. Thepercussion lock (also caplock) was adapted from the flintlock firing mechanism, with thecock being modified to strike a small cup-like cap containing percussive material. The cap was placed over an externalnipple, which acts as an anvil and conduit to ignite the main propellant charge within the breech. In this use, thecock has come to be termed ahammer.[5]
Samuel Colt'sColt Paterson revolver of 1836 used percussion caps. The hammer and other components of the firing mechanism are mounted between the sides that form the frame. While not unique, percussion and flint-locks more typically use aside-lock firing mechanism, with the components mounted either side of the mounting plate.
The caplock was in wide use for almost five decades until the widespread introduction of theself-contained cartridge which contained the projectile, gunpowder, and percussion cap all in a single shell that could be easily loaded from thebreech of a firearm.[5] The introduction of such a technology led to the implementation of thefiring pin and hammer system that is even now still used in certain designs. Whereas the percussion cap in the caplock mechanism was external, the percussion cap in a self-contained cartridge is inside the breech. It is therefore necessary to use afiring pin (a thin rod) to strike the primer through a small penetration in the breech and cause firing.[6]
An external hammer is one that can be accessed by the operator during use. This allows the hammer to be manuallycocked or eased (uncocked) without firing. The hammer is designed with aspur (extension) to facilitate manual operation. An internal hammer cannot be accessed manually during operation. Pistols and shotguns in particular, which have an internal hammer may be referred to as beinghammerless.[7]
Astriker is a type of firing pin operated by the direct action of a spring rather than by a hammer striking the firing pin. Striker-operated firearms lack a hammer.
There are some notable drawbacks to the external hammer system compared to other modern, internal designs. Insingle-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 thetrigger is actually pulled.[8] Even so, many single-action revolver owners choose to carry their revolver with the hammer resting on an empty chamber to minimize the risk of accidental discharge. Additionally, for those who carry their firearm as a personal defense weapon, there is the ever-present worry that an external hammer may catch on a loose article of clothing in an emergency situation, because the hammer protrudes at an angle from the rear of the weapon, and as the owner moves to quickly draw their weapon, the hammer may snag on clothing and cause the loss of seconds in a dangerous situation. Paul B. Weston, an authority on police weapons, called the external a "fish hook" that tended to snag clothing during a fast draw.[9]
A linear hammer is similar to but differs from astriker in that the hammer is a separate component from the firing pin.[10] When released, a linear hammer, under spring pressure, slides along the bore axis rather than pivoting around a pin placed perpendicular to the bore, as with the more common rotating hammer. The hammer then impacts the rear of the firing pin. Designs such as the AmericanM50 Reising, SwissRexim-Favor, ItalianSpectre M4, Czechvz. 58 and the ChineseQBZ-95 utilize a linear hammer.[11]
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