Handgun Information: Single Action vs. Dual Action
Traditional handguns, either revolvers or semiautomatics, have actions that must follow sequentially for the gun to fire. Some guns are called single-action firearms because the shooter must do each act separately from another (single-action only, or SAO). An older "cowboy" pistol is an example of this.
Some handguns, though, work via a different mechanism where one action by the shooter performs multiple actions by the firearm. These are called dual- or double-action firearms (dual-action only, or DAO).
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How single action works
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On a revolver, the cocking mechanism (to which the hammer is attached) is manually pulled back until the gun is "cocked." It is then held in place by a safety device until the trigger is pulled, which releases the hammer and allows it to move forward and strike the firing pin, which in turn strikes the primer on the cartridge, firing the bullet.
On a semiautomatic pistol, the hammer is usually pulled back initially when the slide is manually moved toward the rear of the gun, which also moves the first round from the magazine to the firing chamber. From that time on, each time a round is fired, the slide moves back automatically, which again sets the hammer and makes the firearm ready for the next trigger pull.
Good points/bad points
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Because the trigger is only required to do one action, the amount of energy required to pull it is often must less than a DAO pistol, which means the firearm stays on target easier. With two separate actions needed to fire, many people think the firearm is safer. It is virtually impossible to fire an uncocked gun if someone is startled and grabs it while pulling the trigger
Under stress, many people have difficulty with fine motor control, which can lead to an inability to properly handle the multiple movements needed with a SAO firearm. Without significant practice, they can be slower to put into action than a DAO, which needs only one movement. And with a SAO semi-auto such as a Colt 1911-1A, many people carry it "cocked and locked," or ready to fire without needing to cock it again. Even with a safety device used, this is perceived by some as dangerous as it only takes a small amount of pressure on the trigger to fire.
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How dual action works
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A DAO pistol, either revolver or semi-auto, works by a single pull of the trigger, which both cocks the hammer and releases it to strike the firing pin. Each pull of the trigger works the same way. Some DAO semi-autos such as the Kel-tec models have no hammer that can be cocked, but instead they use a striker system to ignite the primer.
Good points/bad points
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DAO firearms are popular because they have less manipulation to practice and master. They are often called Ph.D. guns (Pull Here, Dummy), or "the original point and click interface." They are quick to learn and to put into action.
Many people consider DAO guns fundamentally unsafe because there usually is no traditional safety on one. The manufacturers claim that they are safe because they are designed to require a much greater amount of pressure and strength to pull the trigger. This, as a result, can make the DAO pistol less accurate with beginning shooters because the effort to pull the trigger can force the muzzle off target.
Other Styles
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Some popular revolvers are made to be either single action or dual action, depending upon the shooter's preference at that moment. If single action is desired, the hammer is merely manually pulled back.
There are some semiautomatic handguns models such as Sig Sauer that are labeled DA/SA, which means that the first shot must be dual action, but instead of returning the gun to the uncocked state of a standard DAO, it leaves it cocked and the second and subsequent shots are fired as a single-action handgun. The Sig provides for an "uncocker" on the side to return the pistol to a safe state when there are more rounds left in the magazine after firing. This action returns it to a DA mode.
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References
Resources
- Photo Credit gun image by dinostock from Fotolia.com
