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  1. #1
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    Default DAO vs DA/SA vs SA/DA???

    I posted this in another thread, but it was suggested that it warrants its own thread, so here goes:

    Ok, I haven't really found a clear-cut answer to my question, so I'll piggy-back it onto this thread (I received a partial answer in another thread but didn't want to derail from the original topic too far). What is the difference between SAO, DAO, DA/SA, and SA/DA triggers in a semi-auto pistol? I'm going to be new to semi autos in the near future, and am just looking to get more informed about the multitude of options available.

    I understand the difference between SA and DA when discussing revolvers, but when the action becomes combined on a semi it confuses me a bit. It was my understanding that when the slide moves backward after firing, it ejects the spent shell and re-cocks the hammer, and then when it moves forward it chambers the next round so it is ready to fire again.

    This is why, I thought, the de-cocker (sp?) that some models have, would bring the hammer to a rest and render the pistol not live until it was re-cocked. It was always my impression that semi autos were single action triggers, and the slide simply re-cocked the hammer, providing the second action.

    If it is a DA trigger, then the slide re-cocking the hammer really isn't necessary is it?
    - I support Israel; "If guns kill people my pencil causes bad spelling."

  2. #2
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    Default Re: DAO vs DA/SA vs SA/DA???

    DA/SA is like a Beretta 92F M9: the first shot is a long, double-action pull. After the slide cycles, the hammer is left cocked back in single-action mode and works as an SA for subsequent shots. Some people don't like the change in pull.

    ETA: Similar thread here: http://forum.pafoa.org/concealed-ope...sa-vs-dao.html
    Last edited by angus; March 4th, 2009 at 12:30 PM.

  3. #3
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    Default Re: DAO vs DA/SA vs SA/DA???

    That's the thread I had initially posted in, and another member suggested the topic warranted its own thread. Thanks!
    - I support Israel; "If guns kill people my pencil causes bad spelling."

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    Default Re: DAO vs DA/SA vs SA/DA???

    Quote Originally Posted by imp81318 View Post
    That's the thread I had initially posted in, and another member suggested the topic warranted its own thread. Thanks!
    D'oh! Sorry! I just noticed that. I'm an idiot.

  5. #5
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    Default Re: DAO vs DA/SA vs SA/DA???

    Speaking of semi-autos:

    SA (Colt 1911), the shooter physically operates the slide to chamber a round and cock the hammer. When the trigger is pulled the gun fires and the recoil ejects the spent round and chambers a new round and cocks the hammer. The shooter only has to pull the trigger to release the hammer. Typically a light trigger pull to release.

    DAO (gun with no decocker or safety), shooter physically operates the slide to chamber a round. This action does not cock the hammer. Shooter must pull the trigger to cock and release the hammer. The recoil ejects the spent round and chambers the next round. It does not cock the hammer and the shooter must again pull the trigger to cock and release the hammer. Basically it acts like a revolver that rotates the cylinder automatically rather than by the action of pulling the trigger. Typically a heavier, longer trigger pull to release.

    DA/SA (decocker models), the shooter physically operates the slide to chamber a round and cock the hammer. The decocker (manually operated by the shooter) releases the hammer (not allowing it to hit the firing pin). The shooter then must pull the trigger to cock and release the hammer. After the first and subsequent shots, the recoil ejects the spent round and chambers the new round and cocks the hammer. The shooter only has to pull the trigger to release the hammer. Typically a heavier, long trigger pull for first shot then a lighter trigger pull. There are probably decocker models that are DAO also (a bit redundant IMO).

    DA/SA (safety models), the shooter physically operates the slide to chamber a round and cock the hammer. In some guns the safety releases the hammer (not allowing it to hit the firing pin) and in others it blocks the hammer. In many cases it also either blocks the trigger or disconnects it. The shooter then must move the safety into the fire position and pull the trigger to release the hammer or to cock and release the hammer. After the first and subsequent shots, the recoil ejects the spent round and chambers the new round and cocks the hammer. The shooter only has to pull the trigger to release the hammer. Typically a heavier, long trigger pull for first shot then a lighter trigger pull. There are probably safety models that are DAO also (again a bit redundant I would think, like putting a safety on a DA revolver)

    SA/DA, I'm not sure about this. I'm sure if something was made that operated like this one of our members will identify it.

    This is just the basics, and I'm sure I probably left something out. That is what is good about the forum, the others will fill in any information I might have overlooked.
    Ron
    USAF Ret E-8
    NRA Endowment Member

  6. #6
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    Default Re: DAO vs DA/SA vs SA/DA???

    Thanks alot Xringshooter! That certainly clears it up quite a bit! FYI, here is a response I got from another member in a thread about a Taurus I was looking at:

    Quote Originally Posted by stephpd View Post
    SA/DA. This is an unusual trigger. Every shot is Single Action unless you have a misfire. Then it turns into a Double Action and give you a second (third) try to fire the round. Many guns are just the opposite. Double Action for the first shot and Single Action for every other shot. Problem is that it's the first shot that's most important.
    Apparently, Taurus is one of the few that uses a SA/DA trigger.

    I think, from a safety stance, I like the SA only because unless you cock the hammer, there is no way for it to go off.

    (BTW, you just got my first rep point...)
    Last edited by imp81318; March 4th, 2009 at 02:24 PM.
    - I support Israel; "If guns kill people my pencil causes bad spelling."

  7. #7
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    Default Re: DAO vs DA/SA vs SA/DA???

    Good point about the second pull ability for a misfire, I forgot about that one. See, I told you a forum member would add if something was forgotten.

    You said "I think, from a safety stance, I like the SA only because unless you cock the hammer, there is no way for it to go off."

    Welllll, a SA like a Colt 1911 (one without a firing pin block) can go off if there is one in the chamber as a sufficient blow to the rear of the gun could send the firing pin into the primer. The 1911 is actual safer when the the gun is loaded, one in the chamber, the hammer cocked and the slide safety on (cocked and locked). This is called Condition One carry and if the gun does not have a firing pin block it is the safest way to carry unless you carry without a round in the chamber. Why would you do that? In a tense situation you would have to remember to rack the slide to get it ready and what if you were already injured and couldn't rack the slide, all you would have then is a very short club.

    Oh, and thank you for the rep.

    When I carry a 45 it is cocked and locked and several of my 45 carry holsters have the strap the goes between the hammer and the back of the slide giving one more safety piece. Unsnap, unholster, slide safety off, pull trigger, boom.
    Last edited by Xringshooter; March 4th, 2009 at 05:37 PM. Reason: additional info added
    Ron
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    Default Re: DAO vs DA/SA vs SA/DA???

    Not sure what you would classify the trigger on my HK USP compact. When you rack the slide and load the gun, the hammer is back. The gun allows you to put the safety on in this condition so you only have a SA trigger pull. You can also use the decocker and put the safety on with the hammer down. This makes the first pull DA and the rest SA.
    Carlos Norman Hathcock II, the original American Sniper

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    Default Re: DAO vs DA/SA vs SA/DA???

    There are also striker fired actions like Glocks. These hold the striker in sort of a half cocked position until you pull the trigger. Glocks were imported first in the 80s and ATF classified them as DA semi autos as there was no other class to put them in. I believe they still classify Glock type actions as DA.

  10. #10
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    Default Re: DAO vs DA/SA vs SA/DA???

    I'll give the best explanation I can regarding trigger types with semi-auto pistols:

    DAO (Double-Action Only): The firing pin/hammer is unlocked prior to firing. The pull of the trigger both cocks the firing pin/hammer and then drops it, firing the chambered cartridge. After firing, the firing pin/hammer is returned to "decocked" position; same as you would find in DA revolvers. For this reason, most DAO semi-suto pistols are NOT equipped with a manual safety.

    DA/SA: The firing pin/hammer is uncocked prior to firing. The pull of the trigger both cocks the firing pin/hammer and then drops it, firing the chambered cartridge. After firing, the firing pin/hammer remains cocked, resulting in a shorter, lighter trigger pull for subsequent follow-up shots. Many pistols in this group are equipped with a manual safety and/or "decock" lever; that when activated (set to "Safe"), returns the firing pin/hammer to "uncocked", and thus returning the trigger to the longer, firmer double-action (DA) pull.

    SA: The hammer/firing pin is cocked whenever a loaded cartridge is in the chamber. These pistols are carried "cocked and locked," meaning the firing pin/hammer is cocked with the manual safety on "Safe". This is typically found in the case of 1911-style pistols. However, Springfield "XD"-series pistols typically don't have a manual safety; however are equipped with both a 1911-style grip safety, as well as a Glock-style trigger safety that makes carrying the pistol as safe as would be with a 1911 with grip and manual safeties.

    SA/DA: Found in Taurus' model pistols, this set-up maintains a "cocked" firing pin whenever the chamber is loaded. However, if the primer of the chambered cartridge fails to ignite upon firing, the trigger releases to a heaver double-action (DA) pull, allowing the shooter an opportunity to re-attempt firing the same cartridge before manually racking the slide to eject the malfunctioning round and chamber a fresh one. Newer SA/DA Taurus pistols also have a "decocker" incorporated into the manual safety, either allowing "cocked and locked" carry when the manual safety is set to "Safe", or "uncocked and locked" carry when the manual safety is pushed upwards past the "Safe" position to decock the firing pin. (On models with decocker safeties, a red "Firing Pin Status" incidator will appear at the back of the slide to denote a "cocked" status.)

    I hope I got all that right. If I'm wrong, somebody feel free to correct me.

    Hope that makes it understandable.

    -38SnubFan

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