doubleactiononly

Double-action-only, often abbreviated as DAO, refers to a firearm action in which every trigger pull cocks and then releases the hammer or striker to fire a shot, with no option to manually cock the hammer for a lighter, single-action shot. In true DAO designs, there is no accessible mechanism to thumb-cock the hammer, and the trigger must perform both actions on each successive pull.

In operation, the trigger pull in a DAO system is typically longer and heavier than in single-action or DA/SA configurations. The hammer or firing pin is moved to the ready position solely by the trigger, and after each shot the mechanism resets for another full trigger pull. This creates a consistent, repeatable trigger feel from shot to shot, which some shooters value for safety and predictability.

DAO designs are found on both revolvers and semi-automatic pistols. On revolvers, the absence of a manually cockable hammer means every trigger pull also indexes the cylinder and cocks the hammer. On pistols, the DAO trigger path is the only path to firing, as opposed to DA/SA or modern striker-fired systems, which may offer lighter, shorter first pulls or separate conditions for first and subsequent shots.

Advantages of DAO include a uniform trigger pull that can reduce accidental discharge for some users and a straightforward mechanism with fewer manual adjustments. Disadvantages often cited are a heavier, longer first-shot trigger and potentially slower follow-up shots compared to firearms with a cockable or lighter first trigger. The choice between DAO and other action types depends on training, preference, and intended use.