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revolver mechanisms

Discussion in 'Gunsmithing and Repairs' started by Nicodemus38, Dec 18, 2009.

  1. Nicodemus38

    Nicodemus38 Well-Known Member

    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.
  2. dfariswheel

    dfariswheel Well-Known Member

    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.
  3. Lee Roder

    Lee Roder Well-Known Member

    Last edited: Dec 19, 2009
  4. Jim K

    Jim K Well-Known Member

    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.

  5. Lee Roder

    Lee Roder Well-Known Member

  6. chocolate

    chocolate member

  7. Jim K

    Jim K Well-Known Member

    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.

  8. Lee Roder

    Lee Roder Well-Known Member

    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?
  9. Jim K

    Jim K Well-Known Member

    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.)

    Last edited: Dec 22, 2009
  10. Lee Roder

    Lee Roder Well-Known Member

    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.
  11. Jim K

    Jim K Well-Known Member

    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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