DA and SA

[brekneb]

Noob here as you can tell from my question.
Okay confused on Double Action and Single Action.

1. As I understand it SA used to refer to revolvers only.--Not the case anymore.
2. The mechanism required you to manually cock the hammer back THEN pull the trigger and that it would not function in any other way? Is that correct? Why is that? Does the sear not engage the hammer automatically?
3. Okay and so as it applies to auto's and revolvers today (or modern side arms). What are the differences between an SA auto and a DA auto? And an SA revolver and DA revolver?
4. Does an SA auto only function with the hammer cocked at any and all times--it's locked back no matter what?--Or am I again misunderstanding something?
5. And does a DA auto just simply mean you can function it in two ways?--That is until the first round is fired?--whereupon no matter what it's DA?
So does that make the trigger pull then a DA or SA pull?
6. So is that in this way with a DA auto you can choose to carry it hammer down or cocked?
7. And the Glock issue . . . Does this not then bring up a third category of "semi double action" since the hammer is held halfway in between hammer down and fully cocked?
:banghead: Argh I am SO confused on this. It seems like it should be pretty simple and straight forward. Tell me if I asked too many questions or if I should have just simply asked; what's the difference between SA and DA. LOL

Thanks if you can make sense of this garbled mess then you're genius.

 

[TallPine]

1. yeah, certainly referred to revolvers only until semi-autos were invented

2. True for SA revolvers, but a semi-auto pistol would be cocked for you after each shot

3. SA auto - trigger releases the hammer[striker] only
DA auto - trigger cocks hammer[striker] and then releases it
SA revolver - works like you said in #1; typically loaded through a "gate" since cylinder does not swing out but you must remove the center pin (axle) to remove cylinder for cleaning etc
DA revolver - trigger cocks hammer and then releases it in a long pull, or you can usually fire as SA. Cylinder typically swings out for reloading.

4. needs a long answer: conditions #1, #2, #3 etc

5. see #2, generally refers to "double action" of trigger. Lots of variation in semi-auto pistols ... some can be fired SA (hammer pre-cocked), DA on first shot only (hammer de-cocked), and then there is DAO which means "double action" only on all shots

6. basically yeah, unless it is DAO (see #5)

7. I dunno much about Glocks, except they don't really have a hammer at all - basically they function about like a SA auto without a safety, at least from the user's perspective

Thanks if you can make sense of this garbled mess then you're genius.

No, but I used to work a gun counter in a HW store. I used to explain this stuff to people, but it's easier when you can show and tell, instead of just tell. You really need to find a helpful gunstore clerk (a rare and endangered species in most areas) or a local gun nut to patiently demonstrate.

 

[Technosavant]

A double action handgun cocks AND fires with the pull of a trigger. For a single action handgun to fire, the firing mechanism (hammer or striker) MUST be cocked before firing. There are also DA/SA guns (see Beretta 92/96) that can fire off the first shot DA (hammer not cocked), but will then function as a SA for the rest of the magazine (the hammer is cocked under recoil and stays that way until it falls on an empty chamber or the user uncocks it).

Glocks are closer to a DA than SA, but they are kinda in between.

Most "modern" revolvers are DA. About the only SA ones out there are for cowboy shooting, collectors/history buffs, and some hunting revolvers.

As for autos, you can't really generalize. SA is by far the minority in terms of current models, and is mainly upheld by the 1911 and Browning High Power (although the Springfield Armory XD also qualifies as an SA; the striker must be cocked to fire). DA/SA and DAO (Double Action Only) are probably the most popular. Very often, autoloaders labelled as "DA" are really DA/SA and are only double action for the first shot.

The determining factor is whether or not the trigger cocks the firing mechanism. If it does, it is a double action. If not, it is single action.

I won't even get into the preference debate.

 

[brekneb]

No, but I used to work a gun counter in a HW store. I used to explain this stuff to people, but it's easier when you can show and tell, instead of just tell. You really need to find a helpful gunstore clerk (a rare and endangered species in most areas) or a local gun nut to patiently demonstrate.

LOL yeah PRECISELY my proble--there are none that are helpful really around me but the people here (you included) have helped and continue to help me immensely.

won't even get into the preference debate.

No, certainly not heh heh


So still a little confused on some things:

1. Why does SA describe the trigger action in an auto and yet also refers to “non-modern” design revolver’s action? (The cock hammer/pull trigger thing?)
Basically why does the term refer to both? Seems confusing--seems like it’s saying a SA trigger pull on an auto is no different than the SA trigger pull on a revolver. Or is there no difference?

2. More specifically on SA autos then.
Is an SA auto SA no matter what? (Hammer always cocked and you can never lower it)

3. Okay with a DA auto you have the option (first round only of course) to carry it hammer cocked (SA) or hammer down (DA) but no matter what, of course, after that first round it’ll be firing in SA correct?

4. I wouldn’t think so but there are no revolver designs which automatically cock the hammer back right?
So unless you manually cock the thing a revolver will always fire in a long heavy DA pull?

5. Then a DAO means you can never cock the hammer back--it's always down?--So what is the mechanism that causes this (or lack thereof)

6. So is there such a thing as SAO auto?

7. And one last thing; striker/hammer are they one in the same--just separate terminology?
Thanks again. I owe huge here.

 

[GunnySkox]

1. Why does SA describe the trigger action in an auto and yet also refers to “non-modern” design revolver’s action? (The cock hammer/pull trigger thing?)
Basically why does the term refer to both? Seems confusing--seems like it’s saying a SA trigger pull on an auto is no different than the SA trigger pull on a revolver. Or is there no difference?

The trigger pull will probably be different because Autos and Revolvers are just built fundamentally differently, I expect.

However, "Single Action" just refers to the fact that the trigger on those guns does one thing, and one thing only: release the hammer. On a Single-Action revolver, you have to cock the hammer again before you can fire again. On a single-action auto, the movement of the slide backward just does that step for you, the hammer still has to be cocked back before the trigger will do anything.

2. More specifically on SA autos then.
Is an SA auto SA no matter what? (Hammer always cocked and you can never lower it)

Whether a gun is cocked or not and whether its single action aren't really...

If a gun is Single Action Only (in that its trigger does nothing but drop the hammer, ever), it's usually written SAO (most 1911s and Browning Hi-Powers are SAO. The hammer has to be cocked for the trigger to have any effect on anything).

Some guns (SAOs or SA/DAs) have decockers, which will drop the hammer safely, even if the chamber is loaded. On some other guns (e.g., my 1911), you have to pull the trigger and "ride" the hammer down to have it loaded and uncocked (as I understand it, this can be dangerous if the gun isn't designed for that. I'm pretty sure most SAO guns aren't intended to be carried/operated/left hammer down on a loaded chamber).

3. Okay with a DA auto you have the option (first round only of course) to carry it hammer cocked (SA) or hammer down (DA) but no matter what, of course, after that first round it’ll be firing in SA correct?

Yes, as long as the auto is operating properly, the slide should cock the hammer back after every shot, except in the case of Double Action Only (DAO) guns, which always require the double-action pull to cock and fire the gun.

4. I wouldn’t think so but there are no revolver designs which automatically cock the hammer back right?

There's one "autorevolver" design which does cock the hammer back for you, but it's not really within the scope of this "Basic" answering.

So unless you manually cock the thing a revolver will always fire in a long heavy DA pull?

Yeah.

5. Then a DAO means you can never cock the hammer back--it's always down?--So what is the mechanism that causes this (or lack thereof)

Yeah. I dunno what the mechanism is, but the hammer usually just rides the slide back down to its resting position.

6. So is there such a thing as SAO auto?

Yeah, I mentioned a couple above (1911, BHP), and I'm sure there're lots of others.

7. And one last thing; striker/hammer are they one in the same--just separate terminology?
Thanks again. I owe huge here.

Striker-fired guns and hammer fired guns operate on the same basic principle (whack a primer with a somewhat pointy pin to make it go bang), but differ on how they perform the whacking. I'm sure you can imagine how a hammer works, but I'll leave it to someone more knowledgeable than me to tell you everything you ever wanted to know about strikers.

~GnSx

 

[Lupinus]

Basically-

A double action on the trigger pull does two actions, the first being cocking the firing mechanism and the second being releasing it.

A single action only releases the firing mechanism because the firing mechanism is either cocked by the action where the slide does it on firing in the case of an auto loader or manually by the user in the case of a SA revolver.

A DA/SA generally fires the first shot DA and remaining shots SA. This way it can be carried without it being cocked and have a heavier pull, making it less likely to accidentally fire.

As for trigger pull DA has a heavier and longer trigger pull because it has more things to do. Some people prefer the SA for the lighter and shorter trigger pull which makes for faster follow up shots.

 

[Lupinus]

More specific to your questions

2. The mechanism required you to manually cock the hammer back THEN pull the trigger and that it would not function in any other way? Is that correct? Why is that? Does the sear not engage the hammer automatically?

In the case of a revolver it was used before they figured out DA would be my guess, today though the only SA revolvers are really for cowboy shooting or collecting....or people who just prefer single action I know a guy that wont carry anything other then a single action revolver.. Today it is used in autos for its shorter and lighter trigger pull. As for actual production I don't know of any current revolvers in production (aside from replicas/cowboy shooting) that are single action only, though if I'm not mistaken can be fired single action if you so choose.

3. Okay and so as it applies to auto's and revolvers today (or modern side arms). What are the differences between an SA auto and a DA auto? And an SA revolver and DA revolver?

Same for both, the hammer is cocked by something other then the trigger if it is SA, or by the trigger pull if a DA. In a revolver your thumb in an auto by the slide.

4. Does an SA auto only function with the hammer cocked at any and all times--it's locked back no matter what?--Or am I again misunderstanding something?

Most SA gun have some sort of decocker.

1. Why does SA describe the trigger action in an auto and yet also refers to “non-modern” design revolver’s action? (The cock hammer/pull trigger thing?)
Basically why does the term refer to both? Seems confusing--seems like it’s saying a SA trigger pull on an auto is no different than the SA trigger pull on a revolver. Or is there no difference?

Because on a revolver there is nothing to cock it for you, if it isn't done by the trigger pull you do it with your thumb. On an auto though there is the slide which moves back each time the gun is fired, convenient and capable of cocking it for you. Revolvers just have nothing to cock it other then the trigger pull.

3. Okay with a DA auto you have the option (first round only of course) to carry it hammer cocked (SA) or hammer down (DA) but no matter what, of course, after that first round it’ll be firing in SA correct?

Might not be understanding correctly but here goes. No, in a double action auto the slide coming back just doesn't cock it it only ejects the fired case and loads a new cartridge.

4. I wouldn't think so but there are no revolver designs which automatically cock the hammer back right?
So unless you manually cock the thing a revolver will always fire in a long heavy DA pull?

As far as I know

5. Then a DAO means you can never cock the hammer back--it's always down?--So what is the mechanism that causes this (or lack thereof)

The opposite. In a DAO the hammer would be up and pulled down by the trigger pull them coming back up at the end of the pull. The mechanism that causes it to come down is internal and part of the trigger pull.

6. So is there such a thing as SAO auto?

Yes there is. These are guns that always have the hammer/striker cocked when there is a round in the chamber. The first being when you pull the slide to chamber a round it cocks, the rest are done by the action of the gun.

7. And one last thing; striker/hammer are they one in the same--just separate terminology?
Thanks again. I owe huge here.

They do the same thing in different ways. A hammer you can look at and get the idea. Hammer snaps up and the firing pin goes through a hole and hits the primer. Some the hammer is flat and hits something that looks like a little button which in turn hits the primer.

A striker is internal so unless you take a gun apart to look at it is more tricky to figure out.

http://www.utdallas.edu/~roddy/Links/Mauser/mauser.html
That is one of my pistols a Mauser Model 34 which uses a striker (not mine on the page, but I have the same model....nice gun but a pain in the butt...taking apart is a pain and to take out the magazine the release it under the mag and hooks it in there....pain in the butt but a fun little gun reguardless lol). Basically when the action goes back and pulls the striker which is caught in the process by a little mechanism. When you pull the trigger the "catch" lowers and a spring drives the striker forward. On the striker is the firing pin which in turn hits the primer.

Not sure of advantages/disadvantages to hammer vs. striker or vice versa though.

My apologies in advance for any misunderstandings....its 3:30 in the morning here lol

 

[brekneb]

My apologies in advance for any misunderstandings....its 3:30 in the morning here lol

Nope, it’s not the time of day it’s my writing cuz I don’t really know what I’m talking about so it’s hard to write it correctly

Yes there is. These are guns that always have the hammer/striker cocked when there is a round in the chamber. The first being when you pull the slide to chamber a round it cocks, the rest are done by the action of the gun.

Ahhh I think I got it then. This may be the last area of concern before I feel I know everything I should about DA/SA
So basically what is meant by SAO (as it applies to autos) is that there is no external mechanism to drop the hammer safely? So that if you want to carry it Condition No. 1 you pretty much have to carry it hammer cocked? And that the only physically possible way to drop it would be to dry fire it? Or . . . Ride the hammer down on a live chamber?--I said physically possible not safely possible! LOL
I think that’s it.
I cannot express to any of you how much I appreciate all this. Thanks for helping a desperate noob out.

 

[Technosavant]

So basically what is meant by SAO (as it applies to autos) is that there is no external mechanism to drop the hammer safely? So that if you want to carry it Condition No. 1 you pretty much have to carry it hammer cocked? And that the only physically possible way to drop it would be to dry fire it? Or . . . Ride the hammer down on a live chamber?--I said physically possible not safely possible!

Usually they are referred to as SA, not SAO (a gun which also functions as a DA at any time falls under the DA category). And you are pretty much correct that, for mose single actions, you have to ride that hammer down if there is a round in the chamber. Not the best idea, and you still must cock it before firing (not that great an idea either). That is why single actions tend to have safeties.

 

[brekneb]

The opposite. In a DAO the hammer would be up and pulled down by the trigger pull them coming back up at the end of the pull. The mechanism that causes it to come down is internal and part of the trigger pull.

Wut? DAO means opposite? I thought what you're describing would be SA? Now me really
confused.

 

[Archangel]

(note: text in red applies only to semi-automatics. all other text applies to both semi-autos and revolvers)

Single action (SA) - Pulling the trigger does only one (single) thing - releases the hammer from the sear, allowing the hammer to fall and fire the gun. Pulling the trigger while the hammer is already down does nothing. Before the gun can be fired again, the hammer must be cocked again. On an auto, the cycling of the slide cocks the hammer. On a revolver, the hammer must be cocked manually. An SA gun can only fire SA, so it is in essence Single Action Only or SAO, though you generally don't see that term used. SA autos almost always, if not always, include some sort of manual safety, so that they may be carried "cocked and locked" (hammer back, safetly on).

Double action (DA)- The hammer starts down. Pulling the trigger does 2 things (hence "double action") 1. Cocks the hammer 2. Releases the hammer. Optionally, the hammer may be cocked manually, at which point the gun operates as a single action. Again, on an auto, the slide cycling will cock the hammer. The first shot will be DA, and following shots will be SA. Therefore DA autos are sometimes referred to as being DA/SA. Such (auto) guns usually include a decocker to safely lower the hammer without firing the gun. They may or may not include a manual safety. If they do, sometimes the safety will allow for cocked and locked carry, and sometimes the safety will double as a de-cocker, making C&L carry impossible.

Double Action Only (DAO) - Functions like a DA, but without the option of cocking the gun manually. Every shot will be double action. On autos, even though the slide cycling does move the hammer back, there is no mechanism to hold it back, so it follows the slide back forward, just like decocking a DA/SA after every shot. Generally does not incluse a manual safety.

Striker fired - Some designs eliminate the hammer entirely. Instead of relying on the hammer's force striking a firing pin, some designs operate the firing pin (striker) directly. The Springfield XD design is single action (the striker must be pre-cocked, pulling the trigger releases it). The Walther P99 is a DA/SA striker. The Glock is sort of an action and a half. Pulling the trigger moves the striker to the rear and then releases it, but it must be reset before another trigger pull has any effect. In all these cases, the slide cycling will reset or re-cock the striker. Then there is the Taurus 12/7, which is a DAO striker fired gun...

 

[brekneb]

Wow, thanks Archangel and thanks everybody.
Yeah the whole generic generalization/description of things it's really friggin' hard to understand! It's all very intricate and KEYWORD HERE: over-lapping!
I think over-lapping more than anything else. Causes much-confusion. And even the pros who've been in it all their lives still ain't got it straight or got it all let alone noobers.
So yes thanks and thanks again.