Trigger Actions
When I look at firearms online, I see lots of terms like SA, DA/SA, DAO and so on. What do they mean?
What is a Striker Fired/Pre-set action?
Striker fired pistols do not use hammers. The striker or firing pin is held back against a spring and then released to fire the weapon when the trigger is pulled. Examples of this would included the Glock Safe Action Pistol, the Sig Sauer P320, and the Springfield XD, H&K VP series. Striker fired pistols were patented by John Browning in 1899 and have been around ever since. That said the striker fired pistol for wide defense use was popularized after the introduction of the Glock 17 which was designed for the Austrian Military. Striker fired pistols make ideal defensive pistols due to their consistent trigger pull.
What is Double Action?
A double action (DA) works by cocking the hammer back then releasing it to fire the weapon. Commonly double actions have a heavy trigger pull. Many commonly take around 12lbs of force to pull the trigger back and release it.
What is Single Action?
A single action (SA) is when the trigger pull drops a cocked hammer. It is usually lighter than a double action because you are not coking the hammer at the same time. Hammer fired pistols carried in single action typically have a manual safety that needs to be released to fire. Examples of this would include in pistol based on the M-1911 .45 Auto Colt Pistol (.45 ACP) introduced to the Army by John Browning in 1911.
What is DA/SA?
DA/SA refers to Double Action/Single action. What this means is the first shot requires a long hard trigger pull to cock the hammer and fire, then the hammer remains cocked for the next round and fires using a much lighter trigger pull. For many a DA/SA is harder to master than a Striker Fired pistol. Many DA/SA firearms have a decocking lever that moves the hammer safely from Single Action back to Double Action.
What is DAO?
DAO means Double Action Only. This type of pistol only has a long heavy trigger put that will cock the hammer and drop it as it fires. Each round requires this same long trigger pull.
Defensive revolvers are typically fired as DAO however there for many such as a Smith and Wesson 686 the hammer can be cocked and fired as a single action also. There are specifically DAO revolvers that often have a “concealed” hammer that does not have a hammer spur you can cock.
–Castle
