What is a double action only revolver? What visual clues might you have with this type of action?

What Is a Double-Action-Only (DAO) Revolver?

A double-action-only revolver is a revolver that can only be fired by pulling the trigger; there is no single-action mode. In DAO revolvers:

• The trigger both cocks and releases the hammer on every shot. There is no provision for manually cocking the hammer before firing.

• Because the hammer cannot be manually cocked for a lighter single-action shot, DAO revolvers must be fired entirely in double action.

Most DAO revolvers are designed for concealed carry or defensive use, where a consistent long trigger pull is preferred and there is no hammer spur to snag on clothing. Some examples of this design have the hammer spur removed or shrouded, and others feature an internal hammer hidden within the frame.

Note: Removing the hammer spur or shrouding the hammer doesn’t change the internal mechanism — it simply prevents manual cocking and reduces snagging during a draw.

Double-Action vs Double-Action-Only

• In a typical double-action/single-action (DA/SA) revolver, the trigger can be used in double-action mode (cock and release) or, if the hammer is manually cocked, in single­action mode (release only).

• In a double-action-only revolver, the trigger always performs both actions: it cocks the hammer and releases it. There is no single-action function at any time.

This difference is why DAO revolvers are described as having no single-action capability — even if an external hammer is present, the design prevents a manually cocked shot.

Mechanical Comparison: DAO vs Single-Action Designs

Internal Mechanism and Parts Count

A common misconception is that single-action revolvers inherently have fewer parts than DAO/double-action revolvers. While single-action and DAO mechanisms differ, the comparison must be precise:

• In a true single-action revolver, the trigger’s only job is to release a manually cocked hammer. There is no mechanical linkage to cock the hammer, so the internal action is relatively simple.

• In a double-action or double-action-only revolver, the trigger must perform multiple functions — it retracts the hammer, rotates the cylinder, and then releases the hammer on a single pull. This requires additional linkages and spring-loaded components compared to a pure single-action design.

A DAO revolver can still be simpler than a DA/SA design (because it doesn’t include the mechanisms that allow manually cocking the hammer), but it usually has more moving parts than a single-action revolver due to the need to link the trigger to both the cylinder indexing and hammer motion.

Trigger Springs and Mechanism Operation

• Single-action revolvers: The trigger only releases the hammer. The hammer is already cocked manually, so the mechanism is straightforward and the trigger pull is short and light.

• DAO revolvers: The trigger must pull the hammer back and release it, which means it works against the mainspring on each shot. This results in a longer, heavier, and more deliberate trigger pull because the trigger is doing more mechanical work.

Many DAO revolvers are engineered so that the hammer returns to a forward position after each shot, preventing any single-action shot — and ensuring the trigger stroke is always the same.

Why Some DAO Revolvers Lack an External Hammer Spur

Manufacturers often remove the hammer spur or shroud the hammer entirely to improve concealability and reduce snagging when drawing from a holster. However:

• Removing the hammer spur does not change the trigger’s function — it still only fires in double action.

• Some designs hide the hammer entirely inside the frame (internal hammer) to make the profile smoother and more snag-resistant.

These physical variations (exposed vs bobbed vs shrouded hammer) are cosmetic/ergonomic, not functional differences in how the trigger fires the revolver.

Summary (with sources)

Concept	Explanation
Double-Action-Only Definition	Trigger always cocks and releases the hammer; no single-action mode available.
Hammer Variations in DAO	DAO revolvers may have exposed, bobbed, or internal hammers — but none allow manual cocking.
Mechanical Differences vs Single-Action	Single actions have simpler trigger linkage; DA/DAO require trigger linkage to multiple parts.
Trigger Spring/Mechanism Notes	DAO triggers are heavier and longer due to dual function (cock & release).