revolver mechanisms


December 18, 2009, 06:23 PM
can anyone get me a good diagram that shows the proper functiong on f a double action revolver? im having a slightly hard time figuring out how the disconnect mechanism works.

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December 18, 2009, 08:09 PM
What brand?

All brands are different.
The old Colt action is totally unlike the S&W which is totally unlike the Ruger.
Plus, DA revolvers don't have a "disconnect" mechanism.

Lee Roder
December 19, 2009, 10:36 AM
here's a pretty generic animation

as stated above, specifics depend on gun maker's engineering dept

Jim K
December 19, 2009, 07:38 PM
That is not a very good drawing, mainly in the cylinder stop. It shows the trigger pushing up on the cylinder stop, when in every revolver I know of with a separate cylinder stop (not part of the trigger), a cam on the trigger pulls the stop DOWN to disengage it from the notch in the cylinder then, after the cylinder turns enough to make sure the stop won't drop back in the same notch, releases it so a spring can push it back up to drop into the next notch and stop the cylinder at the right point.


Lee Roder
December 20, 2009, 09:55 AM
good call. yes the stop and/or trigger have apparently "broken". here's a more realistic animation

December 21, 2009, 06:10 AM
sorry i can not make a diagramme for you but i can suggest a site that will help to complete your purpose that is go on that site and solve your problem.

Jim K
December 21, 2009, 08:07 PM
That is pretty good. They did miss the secondary cam on the S&W hammer and trigger but then quite a few folks, including some revolver experts, don't know what it is or what it does.


Lee Roder
December 21, 2009, 09:23 PM
Fortunately, I'm no expert here :) so I think I'm ok asking what is "the secondary cam" on the hammer and trigger? :evil: You mean the little bevel on top of the trigger nose?

Jim K
December 22, 2009, 10:30 PM
Hi, Lee.

To understand, take the sideplate off an S&W revolver (you should have relieved mainspring (hammer spring) tension before doing so) and take out the mainspring.

Then operate the double action slowly (watch that the edge of the hammer doesn't hit the frame and dent that little point). As the trigger cams the hammer back using the hammer strut (S&W calls it the sear), there is a point where a cam on the trigger engages a surface on the hammer, the bottom of the part the single action notch is in. As the trigger moves back further, that surface takes the tension and the strut is free, that is it no longer bears on the top of the trigger. It isn't too easy to explain but I think you will see what I mean if you watch the action.

In a Colt or most other revolvers, as the trigger pushes the hammer back, the strut and the top of the trigger start to become parallel, plus the spring tension increases. The combination causes the trigger pull to become progressively harder, a result known as "stacking." By using that camming action, S&W changes the trigger-hammer leverage at a critical point and the trigger pull remains at a constant tension throughout, enabling more accurate double action firing.

(FWIW, that camming action is what is called the S&W "short action", as opposed to the older long action which did keep stacking to a minimum through the shape of the trigger and strut.)


Lee Roder
December 23, 2009, 08:28 AM
Wow thanks. Learn something new here everyday, really do.

More on mechanisms, stacked triggers, etc ... in your experience, has a "timing diagram" for any revolver ever been published? By that I mean a plot of various quantities such as torque on trigger, hammer displacement, etc, all as a function of angular trigger displacement? A formal characterization of "when things happen" (or are supposed to happen) at a glance? Pictures are worth a thousand words. I've been unsuccessful finding something like this.

Happy holidays.

Jim K
December 23, 2009, 07:00 PM
Such a thing would be useful, but the closest is the Kuhnhausen books, which I strongly recommend. Check Brownells or one of the book sites.


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