My dad has a S&W SD40 that i took apart and cleaned. I thought they have a DA trigger. After in put the side back on and pull the trigger the hammer releases...but then i pull the trigger again the hammer doesn't fall. Am i miss remembering?
It is basically a single action with a long heavy pull. When a round is chambered it partially cocks it and the trigger pull fully cocks and then releases the firing pin. It results in a better than double-action only trigger but worse than a single-action trigger.
The reciprocating action partially cocks the striker. Few striker fired guns allow a second strike on the same cartridge. Many makers call their striker fired guns "double action" or "double action only". To me this is a serious misnomer. The term double action refers to a mechanism that can be fired two different ways; manually cocking (with your thumb) or trigger cocking (think Smith and Wesson revolver). They have used a term familiar to shooters to describe the "feel" of the trigger, when technically it is incorrect.
Striker fired pistols are considered DAO. Like the Glock. Personally, I prefer striker fired pistols for self defense use.
And I think the term DAO is a misnomer. Double Action is TWO actions. DAO is ONE action. It is an attempt to simplify the naming process like calling all Armalite pattern rifles "AR-15's"
