single vs double action in semi auto

[Miss88]

I have a question which may be elementary for a lot of you. When talking about a semi auto handgun, what does single vs double action mean? I understand the difference in revolvers, but I don't with semi auto's.

[JohnK3]

Pretty much the same thing.

Single-action auto means you pull the hammer back before pulling the trigger or the action cocks the hammer before pulling the trigger.

Double-action means you can lower the hammer to half-cock (or, if you're really brave, lower it all the way) then pull the trigger and it will cock the hammer during the trigger pull before dropping it on the firing pin. Then there are striker-fired, which are generally double-action only, being cocked by the pull of the trigger, rather than the action cycling. (There may be some single-action striker-fired autos, but none come immediately to mind.)

DA/SA can fire both ways.

DAO can only fire double-action (trigger pull cocks the hammer)

SA can only fire single-action (cock the hammer, then pull the trigger)

[Bruce FLinch]

Well defined, John

[Miss88]

Originally Posted by JohnK3

Pretty much the same thing.

Single-action auto means you pull the hammer back before pulling the trigger or the action cocks the hammer before pulling the trigger.

Double-action means you can lower the hammer to half-cock (or, if you're really brave, lower it all the way) then pull the trigger and it will cock the hammer during the trigger pull before dropping it on the firing pin. Then there are striker-fired, which are generally double-action only, being cocked by the pull of the trigger, rather than the action cycling. (There may be some single-action striker-fired autos, but none come immediately to mind.)

DA/SA can fire both ways.

DAO can only fire double-action (trigger pull cocks the hammer)

SA can only fire single-action (cock the hammer, then pull the trigger)

So a "double action only" semi auto doesn't have the hammer cocked by the action at all while shooting your way through a mag? Is there any advantage to this? I am looking at some Hi Point firearms from MKS that are double action only but having second thoughts. It seems that this would decrease accuracy, would it not?

[JohnK3]

Originally Posted by Miss88

So a "double action only" semi auto doesn't have the hammer cocked by the action at all while shooting your way through a mag? Is there any advantage to this? I am looking at some Hi Point firearms from MKS that are double action only but having second thoughts. It seems that this would decrease accuracy, would it not?

Theoretically, yes. However, don't forget that one of the fastest IDPA champs around, Jerry Miculek(sp?) uses a revolver, which is DAO for every shot he makes.

The theory behind DAO semi-autos is that a DAO is *supposed* to reduce your liability in a shooting. The theory is that a SA semi-auto might be "accidently" discharged while you have a perp under your sights, while a DAO takes more effort.


THEORY FOLLOWS, MERELY CONJECTURE:
DAO semi-auto liability theory was possibly developed to skew contracts for police departments towards GLOCKs. Since GLOCKs are DAO, and at the time they pretty much owned the DAO market, procurement officers with preference for GLOCKs may have used DAO as a way to guarantee GLOCK would be chosen for a mass-procurement. This would most likely have been a result of excellent marketing by GLOCK salesmen, explaining the rationale behind DAO.

[Pistolenschutze]

Keep in mind too, Miss, that with a traditional DA auto, only the first shot is DA. The others that follow it will fire with the much lighter SA trigger; i.e., the hammer is left cocked by the action of firing the first shot, thus the following rounds are fired with much less pressure and trigger travel to drop the hammer on the next round.

[JohnK3]

Correctemundo, PS.

The "traditional" DA auto is also called a DA/SA for that very reason. A DAO (Double-Action Only) auto never goes into SA, even if you've just fired it.

[Miss88]

OK thanks, that answers my questions. I looked at some other makes and there are a lot of DAO semi auto's out there, so it's not a niche market, pretty much mainstream. Thanks all.

[delta13soultaker]

I personally like it when every trigger pull is the same....either DA or SA. (1911, Glock, DAO revolver etc etc)

I came to that preference from dealing with M9's (Beretta 92) because that first shot was rough and the second too easy. Just seemed unnecessary in a fighting pistol; figured we could do better.

[stash247]

Miss 88, et al:
DAO has TWO faces. Beretta builds a DAO M-92, whick cocks and drops the hammer, full force, every time the trigger is pulled, just like a S&W revolver; Glock, also considered DAO, by most, and Kahr, do not! Both Kahr, and Glock, require slide cycling to 'half cock' the striker, the trigger doing the rest. Consistant pull, when the gun runs, but "no joy" (read this, immediate action drill:"Tap-Rack-Bang") if it does not!
The Beretta, and the S&W 39/59 crowd, will at least, give a full force swat, to the same (dud?) round, if the trigger is pulled again! Same applies to Walther, in the PP, and P, series pistols.
S&W Revolver, action is the same; ie, pull the trigger again, except you get a new round in the breech, every pull of the trigger!
Draw your own conclusions, based on application, ability, budget, and energy requirements.
My personal choices are (1) a compact, 1911 pattern, SA auto, in .45 ACP, with proven (5,000+ rds)reliability, followed by(#2) a S&W 337PD, in .38 Spl, when #1 just won't fit in!