Handgun Action Type: The action is the operating mechanism of the handgun. Generally speaking, all the moving parts of a handgun make up its action. Action as it refers to trigger function is broken down into two primary categories: Single Action and Double Action.

 

Single Action Only (SAO)

A SAO trigger performs the single (only) action of releasing the hammer or striker to fire the gun each time the trigger is pressed. If the hammer is not cocked on a SAO gun like a 1911, pressing the trigger will result in no shot being fired.

 

2) Double Action (DA)

DA indicates that pressing the trigger causes two (double) actions at the same time: (1) cocking and (2) releasing the hammer. DA triggers provide the ability to fire the gun whether the hammer is cocked or uncocked.

 

3) Double Action Only (DAO)

DAO guns cannot be fired in SAO mode. DAO guns cannot be manually cocked, since the hammer is only cocked and released by trigger manipulation. The hammer will not be automatically cocked after a shot is fired.

 

4) Double Action/Single Action (DA/SA)

This type of trigger the first shot can be double action or single action, depending on if the trigger is pressed initially for double action or if the hammer is manually cocked back with the thumb for single action, but one press of the trigger does cock and release the hammer if it is not cocked manually.

 

5) Striker-Fired or Partially Cocked Striker (SF)

Striker-Fired guns strictly speaking are neither DAO nor SAO trigger mechanisms. They are striker fired, with their own system, trigger safeties and striker blocks, etc