I'm quite familiar with how the standard S&W SA/DA pistols function and the mechanical interaction between the disconnector, sear, and hammer along with the safety levers. I'm not entirely sure how the DAO pistols function given the hammer follows the slide into battery. I have a 4586 but I haven't disassembled it and studied its guts. I'm tempted to but perhaps someone knows of a site where the DAO action for the S&W is detailed preferably with illustrations or photos. Anyone that has completely disassembled the sear-hammer mechanism on a S&W knows why I'm leary to do so as getting them back together is a minor PITA and a MAJOR PITA if its a decocker model.

Took my 5946 all the way down. Only thing different was no spring installed in the firming pin safety. I threw one in figured I had misplaced it.
Wouldn’t let slide back on. Removed spring all returned to normal. Conferred with two other armorers . They concurred it was not installed. All other dis/ assembly was normal.

The main difference in the DA models is in the design of the hammer. On the DA only hammer, there is only one notch for the drawbar....the throw notch. (there is no pickup notch)

There is also a very distinct "capture" type notch in the hammer for the sear, where the sear rests after slide cycling, waiting for the next trigger/drawbar cycle.

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Ret. LE, FA Instr, S&W Armorer

Cool! When you had it apart, did you see how the hammer is retarded from striking the firing pin when it follows the slide into battery after firing and cycling? What keeps the pistol from slam firing the entire magazine after the first pull?

After firing, the slide cycles the hammer back, and it follows the slide forward to the point where the sear lands in the capture notch in the hammer. The hammer then stands/waits on the sear in this notch until the next trigger pull moves the drawbar forward again to pick it up for the next cycle. You can see this very pronounced capture notch in the "DA ONLY" hammer in the photo.

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Ret. LE, FA Instr, S&W Armorer

I guess I need to break down my 4586 to understand how the sear catches it on the slide going into battery after firing but doesn't impede the hammer when the trigger is pulled.

No "double-strike" capability in these DAO models either. That's because if the hammer is all the way down, as it is when dry fired, (or mis-fires) the hammer and drawbar are out of position and the drawbar can't pick the hammer up when the trigger is pulled.

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Ret. LE, FA Instr, S&W Armorer

I'll go out on a limb and opine that the 3914DAO and CS DAO guns have double strike, but none of the others.

From the recently posted pictures of the CPD 457D, it has the same hammer as the 3953 and other DAO guns. From which I'm working on the premise that it doesn't have second strike.

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Can open, worms everywhere.

The 3914 and the CS series pistols you mention, along with other similar models, do not contain the same internals as the true DAO (double action only) pistols. Their internals, frames and slides of the ones you mention are the same mechanically as the other SA/DA pistols.....minus the hammer spur. There is no manual safety/decocking lever on the true DAO slides.....no need for one, their hammers don't and won't stay back. No SA notch available to sit on.

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Ret. LE, FA Instr, S&W Armorer

I would love to see a similar picture of the 3914DAO hammer...

Since it doesn’t stop in a “partly-cocked” position like the true DAO guns, what stops it from potentially going full auto? The firing pin safety?

(IIRC, the 3914DAO was a special modded version for NYPD, is DAO, and has restrike...)

Here's a photo of the 3913, 3914 etc hammer. What stops the gun from "potentially going full auto" is the SA cocking notch. After the first round is fired DA by the user, the gun cycles and the hammer (spurless) is held in the SA position on the sear.
In order shooter to fire the gun again with a DA pull, the user would have to de-cock the hammer using the manual safety.

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Ret. LE, FA Instr, S&W Armorer

Yes, I understand that. Question was on the 3914DAO, which presumably doesn’t have the SA cocking notch, doesn’t have a SA mode, and returns to decocked by itself each shot.

Perhaps you're referring to the 3953, 3954?

The 3913 and 3914 don't function the way you describe.

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Ret. LE, FA Instr, S&W Armorer

Ok, let me ask this... Are you aware that there is a 3914DAO model that is different than the 3913 or 3914? Note that I am not saying “3914 DAO”, I am saying “3914DAO”, which is a distinct model. A forum search will show other threads on this pistol.

The 3914DAO is DA every pull, and doesn’t precock. You have the full DA pull every shot. It is like a 3914 without SA capability.

And so I’m wondering how they avoid full-auto or slamfires on this specific model.

No sir, I'm not aware of that model. Never seen one. I'll look it up, thanks.

Perhaps someone who has one wouldn't mind showing the internals, including the hammer design.

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Ret. LE, FA Instr, S&W Armorer

there are and where some guns 3914dao, made for nypd, that would have the double strike action if needed. i missed one on gb, not long ago. no i do not have one, but would like one. be safe....dan

I am definitely not going to take my 3914DAO apart to look at the hammer.

What I can tell you is that I converted a 457 to DAO by taking a donor hammer and filing off the SA notch. The gun worked fine in DA mode and there were no slam fires or full auto to be found.

Everything else was the same as it came from the factory, including the disconector.

My guess is that S&W did the same thing as well. The trigger pull on the 457 version was hard on my forearms when I fired more than a box of range ammo, so I converted it back.

The weather hasn't been good enough for me to get out to the range since I acquired the 3914DAO, so I can't tell you much about that.

Essentially, if fires as if it was firing the first round in a TDA gun all the time.

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Can open, worms everywhere.

I had a CZ v45, a 25acp hammer-fired DAO pocket pistol. It didn’t have any kind of SA or precock notch, nor a firing pin safety of any kind. It just let the hammer follow the slide home.

While it didn’t slamfire, it did put a little dent in the next-up primer. So clearly the firing pin spring was crucial.

Where you bidding on the one about 3-4 weeks ago?

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Can open, worms everywhere.

There is a reason why the 3914DAO (and the CS "D" models) with 2nd strike capability and lacking only the SA hammer notch to differentiate them from the TDA (DA/SA) models, do NOT slam-fire or go full auto.

First, a few words about the S&W firing pins:

As installed in the 1st, 2nd, and 3rd gen pistols, the rear of the firing pin (the part struck by the hammer) protrudes from the safety body only about 1/16".

However, the firing pin must travel about 1/4" (against firing pin spring resistance) before it will protrude sufficiently from the breech face to impact the primer.

Consequently, the firing pin requires a pretty good smack on the "derriere" to have enough energy to ignite a primer.

The hammers on the "2nd strike" DAO models (like the 3914DAO) which follow the slide to rest, simply lack the energy to propel the firing pin the necessary distance.

John