Double action (or double-action) refers to one of two systems in
firearms
A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions).
The first firearms originated in 10th-century China, when bamboo tubes ...
where the
trigger both cocks and releases the
hammer
A hammer is a tool, most often a hand tool, consisting of a weighted "head" fixed to a long handle that is swung to deliver an impact to a small area of an object. This can be, for example, to drive nails into wood, to shape metal (as wi ...
.
*
Double-action only
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 tr ...
(DAO) firearms trigger: The trigger both cocks and releases the hammer. There is no
single-action
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 tra ...
function and the hammer will return to its decocked position after each shot.
**Double Action Kellerman (DAK): A variant of traditional double-action used on certain
SIG Sauer
Several brother companies that design and manufacture firearms use the brand name SIG Sauer . The original company, ''Schweizerische Waggon-Fabrik'' (SWF), later ''Schweizerische Industrie-Gesellschaft'' (SIG), went through several selloffs, ...
semi-automatic pistols. DAK triggers have a long stroke with pull. However, if a user shooting under stress short-strokes the trigger by only releasing it halfway, the trigger will reset, but with a pull. This temporary increased trigger pull is intended to prevent negligent discharges.
*
Traditional double-action
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 ...
– or double-action/single-action (DA/SA) – firearms trigger: The trigger combines the features of both a double-action only and a single-action only trigger.
** With a
revolver
A revolver (also called a wheel gun) is a repeating firearm, repeating handgun that has at least one gun barrel, barrel and uses a revolving cylinder (firearms), cylinder containing multiple chamber (firearms), chambers (each holding a single ...
using this action, the hammer can be cocked first (single action), or the trigger can be pulled and it will cock and release the hammer (double action). Once the gun has fired, the hammer stays in the decocked position until the hammer is re-cocked (single action), or the trigger is pulled again (double action).
** With a
semi-automatic pistol
A semi-automatic pistol is a type of repeating single-chamber handgun ( pistol) that automatically cycles its action to insert the subsequent cartridge into the chamber (self-loading), but requires manual actuation of the trigger to actu ...
using this action, the initial trigger pull will cock and release the hammer (double action). The
blowback from the firing mechanism automatically re-cocks the hammer after the gun is fired, such that each subsequent shot only requires the hammer to be released (single action). A
decocker, if present on the pistol, can be used to return the hammer to its decocked position to prevent negligent discharges.
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