Basic Information
Dual Action refers to a firearm - normally a revolver or self loader pistol - on which the trigger operates in both single action and double action modes. Normally the first shot is double action, and subsequent shots are single action until the weapon is de-cocked or the hammer falls on an empty chamber.
This enables the weapon to be carried (relatively) safely with a round in the chamber and for the user to bring it rapidly into play at the cost of reduced accuracy for the first shot. This system circumvents the inherent weaknesses of both trigger systems to some degree and is increasingly standard in modern handguns. Since the double action trigger cannot cycle the bolt to chamber the first round the user must hand-cock his weapon first and then use a de-cocking lever to lower the hammer until he is ready to fire.
Dual action triggers are rarely found on long arms - most of which can only be cocked by cycling the bolt - but some submachinegun designers have experimented with them, particularly for weapons aimed at the bodyguard market who require to square the circle between being as free as possible from the risk of negligent discharges and yet being able to open fire at extremely short notice.