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Why don't double action revolvers require a transfer bar ?

Discussion in 'Handguns: Revolvers' started by jski, May 24, 2019.

  1. jski

    jski Member

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    Single action revolvers use a transfer bar to prevent accidental discharge of the round in the chamber under the hammer. Why isn't this necessary for double action revolvers?
     
  2. JohnKSa

    JohnKSa Moderator Staff Member

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    It is. Or at least some method for achieving that type of function is necessary.

    Ruger uses transfer bars in their DA revolvers. S&W uses a hammer block bar which has a similar overall effect but that works differently internally.
     
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  3. labnoti

    labnoti Member

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    Yes, Ruger DA's do use a transfer bar and most S&W with exposed hammer spurs actually use two different hammer blocks each. On their concealed hammer j-frames, they typically omit one of the redundant hammer block mechanisms.

    A transfer bar has to stick up between the hammer and firing pin so the mainspring energy is transferred from the hammer through the bar and into the pin. If the trigger is not pulled, the transfer bar is not in place and the energy transfer does not happen as the hammer fails to reach and make contact with the pin. A hammer block accomplishes the same thing but by the opposite means. The block prevents the hammer from reaching the pin by blocking it. If the trigger is kept pulled back then the block is removed allowing the hammer to reach the pin. The reason S&W added a second redundant block is because the first one works as a notch on the mechanism and it could conceivably be overcome if a strong enough blow were to hit the hammer spur. The second hammer block would still prevent the pin from being hit. In a concealed hammer revolver, the notch is regarded as sufficient since nothing external can strike the hammer spur.

    I am not an expert on S&W history, but if I'm not mistaken, S&W began using hammer blocks by at least the 1930's. After WWII they had improved their mechanism and their revolver's drop safety. I'm not sure when they added the redundant mechanism. Ruger, on the other hand, was intentionally making single actions inspired by the 1873 Colt and changing the action wasn't always seen as desirable or necessary, but by the 70's they had come to believe it as at least necessary. It was also in the 70's that Ruger introduced production DA revolver models and thereafter produced both their SA's and DA's with transfer bars.

    Again, if I'm not mistaken, while Colt SA's like the 1873 and the New Frontier (what the Blackhawk copied) did not have hammer blocks or transfer bars, early Colts did introduce safety notches and Colt was probably the first to introduce a hammer block safety in their double action revolvers with their revision to the New Service in 1909.
     
    Last edited: May 24, 2019
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  4. jski

    jski Member

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    and
    which is better?
     
  5. edwardware

    edwardware Member

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    Ruger SAs use a bar that connects the hammer to the pin, and S&W uses a bar that blocks the hammer from the pin. Like Smithwise and Coltwise rotation, it's the same thing backwards.

    Whichever one you've learned to work on to your satisfaction. In my case, I prefer S&W's mechanics.
     
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  6. jar

    jar Member

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    Neither is better; they are simply different routes to the same end.
     
  7. mcb

    mcb Member

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    One could argue the hammer block is better than the transfer bar since you only have two contact points during ignition to lose energy at. Hammer to firing pin, firing pin to primer. With the transfer bar system you have three, hammer to transfer bar, transfer bar to firing pin, firing pin to primer. Clearly not a real world issue for the most part but something to argue about on the internet... :D
     
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  8. Sistema1927

    Sistema1927 Member

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    Which is better? Ford or Chevy?

    (Ducking the thrown rocks.)
     
  9. LoonWulf
    • Contributing Member

    LoonWulf Contributing Member

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    Glock!


    I've only taken one Smith apart, and a number of rugers. Personally, @edwardware said, I think it's which ever one your used to will generally be preferred.
     
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  10. Lucky Derby

    Lucky Derby Member

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    Both systems work. I personally prefer S&W, but have owned a number of Rugers (and Colts) over the years. Never had any issues with any of them.
     
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  11. Waveski

    Waveski Member

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    The transfer bar works , but I am not a fan of that design ; as previously stated :
    There has to be an energy price associated with that succession of transferred strikes , the Smith type system "strikes" me as more efficient.

    In addition , I prefer the traditional hammer mounted firing pin.
     
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  12. jski

    jski Member

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    As an engineer I'd go with whichever involves the fewest moving parts.

    BTW, who invented the transfer bar? The hammer block bar?
     
  13. mcb

    mcb Member

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    I think Iver Johnson may have been it's creator. They have a patent related to it for use in revolvers in 1896. They used a transfer bar in their safety-automatic from that same time period.
     
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  14. .455_Hunter

    .455_Hunter Member

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    Yes- IJ did the "hammer the hammer" safety system on its upper end guns, and also invented the trigger "dingus", supposed Glock perfection be dammed.
     
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  15. sabbfan

    sabbfan Member

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    Charter arms claims they invented the transfer bar safety on their website, true or not I don’t know, but that’s what they claim.
     
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  16. .455_Hunter

    .455_Hunter Member

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    That's funny, because my 1913 production IJ has one, and Charter wasn't started until 1964.
     
  17. labnoti

    labnoti Member

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    The transfer bar incurs a greater loss of energy thereby requiring a stronger mainspring and harder trigger pull for equivalent ignition pressure, but the differences could be very small indeed and other differences in the mechanism such as the fit and finish of the parts could easily negate this.

    The transfer bar also results in repeated impacts on the bar and potential failure, whereas the block does not endure stress under normal operation.

    These differences might be meaningful if you were designing a new revolver and were considering which is better. When evaluating existing Ruger versus Smith & Wesson models, it should be recognized that both makers have succeeded in their designs and in evaluating the end result one does not have a distinct advantage over the other and other distinctions in their models are almost certainly more meaningful.
     
  18. sabbfan

    sabbfan Member

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    • Completely blocked hammer system cannot fire unless trigger is held in full rear position - safest revolver design in the world. In fact, Charter invented the hammer block transfer bar safety system used by almost every revolver manufacturer.
    Copied this from their website just now. Like I said I have no knowledge of the truth if their claim, I had just remembered I had seen this on their site before. And it seems it isn’t true based on your guys’ experience with the Iver’s
     
  19. BobWright

    BobWright Member

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    A revolver with a broken transfer bar will not fire. A gun with a broken hammer block can still be fired.

    Bob Wright
     
  20. Crunchy Frog

    Crunchy Frog Member

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    My first centerfire revolver was a Ruger Security Six so I was well familiar with the transfer bar ignition. Ruger started putting that feature in its single action revolvers in 1973.

    When I started cowboy Action Shooting in 2010 I was amazed that some shooters had paid to have Ruger New Model SA revolvers modified to eliminate the transfer bar and to add a hammer with a halfcock notch. It seemed to me that they were going backwards.

    The explanation was that by eliminating the transfer bar, allowing the hammer to strike the firing pin directly, that the revolver would reliably ignite primers with a lightened hammer spring. There is some “energy loss” in having the transfer bar in the mix, if only a little.
     
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  21. Waveski

    Waveski Member

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    Great point.
     
  22. Monac

    Monac Member

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    The general answer is that transfer bars are not required in all revolvers because when there is greater freedom of form than that required by making a SAA replica, there are a variety of equally effective mechanical solutions to the same problem: that of insuring that the revolver will only fire when the trigger is pulled to rear and held there for the duration of the hammer fall.

    One of the less common ones, but equally effective, was Hopkins & Allen's "Triple Action" mechanism, in which the hammer not only rotated in an arc, but also moved up and down. Pulling the trigger caused the hammer to move down so that the face of the hammer could strike the frame-mounted firing pin; releasing the trigger at any time caused the hammer to move up too high to hit the firing pin, and instead it struck the frame and rested there. As far I as know, only Hopkins & Allen and Llama of Spain used this system; I mentioned it recently in a thread where someone here was considering buying a Llama Comanche revolver.

    I have in my possession a 6-shot H&A .32 Long Safety Police revolver, with the Triple Action mechanism, in which someone has ground off the projecting face of the hammer needed for the system to work. Now the firing pin protrudes into where the primer would be whenever the hammer is down, regardless of the trigger. I bought this gun off the Internet, and did not notice this flaw for months, because I did not take it to the range. Now I need to figure out what to do with it! An effective repair, or even replacing the hammer if an undamaged original became available, would probably cost more than the gun is worth. (It is not in pretty shape - I was attracted to it because it was a 32 Long.)
     
    Last edited: May 24, 2019
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  23. Varminterror

    Varminterror Member

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    “If ya never ask, ya never know.” Now you’ve asked, and now you know.

    Rugers and Taurus DA revolvers do have transfer bars. S&W’s have hammer blocks - as noted above, these aren’t as secure, as the failure mode for the part isn’t a “safer” condition. A broken hammer block means the revolver can fire without the trigger held to the rear, a broken transfer bar means the revolver can’t be made to fire even intentionally pulling the trigger.
     
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  24. Varminterror

    Varminterror Member

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    I agree - this never made sense to me.

    Two reasons they do it:

    1) the one @Crunchy Frog mentioned, to increase the energy transferred to the firing pin by the hammer, allowing ever so slightly lighter hammer springs.

    2) the “insurance” of not having a transfer bar break in the middle of a stage. We shoot our revolvers more in a single competition season than most other revolvers would be shot in a lifetime, even multiple lifetimes, by a non-competitive shooter. Transfer bars break. Some guys don’t want to have one in the cart and pick up miss penalties at a match in the event of a breakage.

    The consequence is relatively low in CAS/SASS anyway, since we all have to only load 5 and carry over the empty chamber by the rules.
     
  25. .308 Norma

    .308 Norma Member

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    Dodge.
    "Dodging" the thrown rocks.:D
     
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