singleaction

Single-action refers to a firearms mechanism in which the trigger performs only one action: releasing the hammer (or striker) that has already been cocked. This is commonly contrasted with double-action systems, where the trigger performs both the cocking and the releasing of the hammer in a single trigger pull. Some firearms are described as single-action only, meaning the hammer must be cocked before each shot and the trigger cannot cock it on demand.

In revolvers, single-action operation requires manually cocking the hammer before each shot. Cocking the hammer rotates the cylinder and align a cartridge; pulling the trigger then releases the hammer to fire. The trigger pull in single-action revolvers is typically light and crisp, but the shooter must perform a separate action for every shot.

In semi-automatic pistols, single-action typically means the hammer is cocked either manually or by cycling the action, after which the trigger only releases the hammer. The first shot may require cocking, while subsequent shots fire as long as the hammer remains cocked. Some pistols are designated single-action only (SAO), with triggers that can only release a pre-cocked hammer and cannot cock it on pull.

Historical and notable examples include the Colt Single Action Army, also known as the Peacemaker, a late 19th-century revolver emblematic of the American West. Other SA systems include older revolvers and certain competition pistols that favor a light, crisp trigger.

In practice, single-action designs offer a light, precise trigger at the cost of requiring manual effort to prepare each shot, making them popular in historical reenactment, cowboy action shooting, and certain precision applications, while many modern service pistols utilize double-action or striker-fired mechanisms for different ergonomics and fire-control characteristics.