Slo-Mo of S&W Revolver Action?

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Mike_Fontenot

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I'm trying to better understand the inner workings of S&W revolver trigger/hammer action (specifically on my S&W686 and my S&W69). Anyone ever seen a slowed-down video of it? I'm mostly interested in SA mode, but also would like to understand how the DA hammer release mechanism is different.

A couple of other questions: Besides the stoning of the SA sear-surface on the trigger, I've seen some videos talking about fine-tuning the lightness of the trigger pull by (1) replacing the "trigger-return spring" with a lighter one (or cutting a winding or two off of the existing one), and/or (2) filing the tip of the strain screw slightly.

From my very limited understanding, it appears to me that the trigger-return spring is what is primarily responsible for the force of the SA sear of the trigger against the tiny ledge in the hammer that is holding the hammer back in SA mode. So I THINK lightening IT would have the most direct effect on the SA pull, and shouldn't affect much else ... is that right? What is the downside of making the trigger-return spring too light? It shouldn't be related to light strikes, I would think.

And I think the strain-screw shortening would affect the torque on the hammer which is trying to make the hammer rotate forward ... so I THINK that would mostly affect the DA trigger pull, and have only a fairly minor effect (compared to the trigger return spring) on the SA trigger pull ... is that right?

Finally, from the little I've seen, the "mating" of the SA sear and the hammer-ledge on the S&W revolvers seems to be quite different than the very simple way the sear mates with the hammer-ledge on a 1911 ... it doesn't look like the motion is simply to lift the sear in a direction perpendicular to the hammer ledge, like it is on the 1911. Anyone seen a closeup photo of that mating arrangement on a S&W revolver?

Any words of wisdom would be much appreciated. (I have the Kuhnhausen shop manual, and haven't found it helpful at all).
 
internals

If the Kuhnhausen manual isn't helping you understand the inner workings of the S&W revolver action, you must have a different book than I have. It's a great reference, answers many of your questions directly, and includes many very high quality illustrations.

I'm not personally aware of any "slowed down" video of the internals at work. You can, however, create your own "slow motion" live by using your own S&W revolver. Simply remove the sideplate and the mainspring, then carefully and slowly cycle the action yourself.

Replacing the rebound spring with a lighter one will lighten both the SA and DA pull. The rebound slide spring does hold tension on the trigger bevel as you describe in your narrative, and it also serves to return the trigger/rebound slide forward when it is released. Too light a rebound spring can contribute to push off, and cause the trigger to not return fully and properly. The proper return of the trigger is also the primary "safety" mechanism should the gun be dropped and the hammer fall, the rebound slide/trigger assy repositioning forward (ahead of the hammer) prevents the hammer from going fully into battery due to the interface of the hammer seat and rebound seat. It also serves to raise the hammer block into position, which is another one of the action driven safeties inherent in the action itself.

Removing material from the strain screw will lighten the tension on the hammer, and may (will) result in misfires.

The interface between the hammer SA cocking notch and the bevel on the trigger in the s&W revolver is physically speaking, much the same as the relationship between the sear and hammer in the 1911. The difference is the hammer notch on the revolver hammer is much narrower, and the action of the trigger pull in the revolver removes the trigger bevel directly from the hammer notch, instead of the trigger acting on a sear through the use of a push from a trigger bow (1911) or pull motion from the drawbar as in the S&W pistols.
 
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Where'd he get that clear sideplate?? :confused:

I would LOVE to have one of those!! :D
 
It seems pretty clear to me, there is no such thing as an accidental shooting, using a modern day S&W DA revolver!

You know, like those stories on the 11PM news..."The gun fell off the nightstand, and shot my wife!", "I was just looking at it, and it went off!"
 
A couple of other internal safeties include the "magnum" pin on the back side of the hand, which prevents the cylinder from opening once the hammer is cocked........and the 3lb factory dictated SA trigger pull, which, when unaltered, is greater than the weight of the revolver.
 
armorer951 said:
[...]
I'm not personally aware of any "slowed down" video of the internals at work. You can, however, create your own "slow motion" live by using your own S&W revolver. Simply remove the sideplate and the mainspring, then carefully and slowly cycle the action yourself.
Click to expand...
I've only got two L-Frames (the other 3 are J-Frames). One (the 69) is my EDC, and the other (686) is my range gun that I shoot every week. I don't want to take either one out of action to try to understand the action. Also, I'm not knowledgeable enough to insure that various parts will stay in place while working the action with the side plate off.

[...]
Too light a rebound spring can contribute to push off, [...]
[...]
Click to expand...

What is "push off"?

The interface between the hammer SA cocking notch and the bevel on the trigger in the s&W revolver is physically speaking, much the same as the relationship between the sear and hammer in the 1911. The difference is the hammer notch on the revolver hammer is much narrower, [...]
[...]
Click to expand...

Here is the video I saw that tells me that the geometry of the sear/hammer mating is quite different in the S&W revolver versus the 1911:

smith and wesson revolver trigger job - YouTube
 
armorer951 said:
[...]
...and the 3lb factory dictated SA trigger pull, which, when unaltered, is greater than the weight of the revolver.
Click to expand...

The two L-Frames I've bought in that last couple of years have had MUCH heavier SA triggers than that ... around 5 lbs. The three J-Frames I've bought over the last couple of decades (including a 3" model 60 bought about three years ago) had very nice triggers right out of the box (probably about 3 lbs), and they improved further with lots of dry firing and live firing. The two L-Frames got immediate trigger jobs by a local gunsmith.
 
I am also going to say that if you can't make sense of the action from reading the Jerry K. shop manual then I would advise highly against trying to do any work on your guns and it would probably be best to quite worrying about it. No disrespect intended, but the Jerry K shop manuals are the most complex and robust gunsmithing manuals made that tell you everything you need to know in order to achieve factory level quality work. Also, Smith revolvers can easily be fudged up if you start tinkering. They are not very forgiving.

With that said, you could easily take the side plate off, work the action, and it will all stay in place.

The rebound spring is responsible for most the pressure in DA and SA. If too light, the trigger won't rebound under a normal pressure mainspring and it will expose 'push off' is your sear isn't 100% perfect. You can correct the trigger not rebounding issue by lightening the mainspring via the strain screw but it must keep the DA pull at least 7# or higher to ensure proper primer ignition. You never want to cut a 'coil or two' off the rebound spring, it will ruin it, must have the full length to work.

Of course the action is going to appear different from a 1911. You are comparing apples to oranges.
 
iPac said:
With that said, you could easily take the side plate off, work the action, and it will all stay in place.
Click to expand...

Well, I've seen in the videos that the firing-pin-block comes right out. What else comes right out? I've seen someone remove the hammer without unlocking anything. And I'd LIKE to remove the hand, because when it is in position it obscures the contact between the hammer and trigger, but I'm not confident I could get it back in position correctly. And what parts can be removed without preventing the action from working normally (as far as the hammer release is concerned)? Too many unknowns (to me) for me to be willing to experiment on it.

You never want to cut a 'coil or two' off the rebound spring, it will ruin it, must have the full length to work.
Click to expand...
That was recommended in the Kuhnhausen shop manual.
 
It's OK to manipulate the action of a revolver with the side plate off if you heed the advice above to do so very carefully! Things can move in ways not intended which the sideplate prevents. The hand is likely about as difficult a piece to get back together as any inside the revolver. It would really be good to have the help of someone who has done it before if you attempt to do that.

One thing I will say with great confidence! DO NOT allow the hammer to fall under full spring tension with the sideplate off the revolver!! Doing so can result in breaking the stud on which the hammer pivots. This is an expensive repair. The pin that the trigger pivots on can also be broken off with the same results ... expensive repair if it's done correctly. Notice that those two studs fit into blind holes in the side plate. This allows both ends of the stud to be fully supported when the internal action functions under normal conditions. That mostly prevents the studs from being broken. Alloy framed revolvers are even more sensitive to this potential problem.

The inside of an S&W revolver is not rocket science, but removing the sideplate and the internals of the action require patience and some understanding of how things work. It's good to know how to do it ... right! Some of us have learned some lessons along the way, mostly about what not to do!
 
Mike,

You and I are close to the same year model! We moved from Lea County in SENM to the Hub City about a year ago. Born and grew up on the east side of Central New Mexico and have lots of experience with both sides of the demarcation line between the two States. Eastern NM and West Texas are more alike than either is like the rest of either State in my experience. The people are the same, the weather is the same, and the living experience is pretty much the same. Am familiar with the Midland area too! I guess, except for the small matter (in my mind, LOL!) of birth certificate, we are about 100% Texicans. Both sons graduated college here and both married Texas girls and all their kids have that "correct" birth certificate. All of us now are Texas residents and liking it very much!

Glad my advice was to your liking. Always hope to help rather than hinder. Thanks for the question too!
 
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