S&W D/A top break trigger in S/A?

Discussion in 'Technical Questions & Information' started by belercous, Dec 28, 2009.

  1. belercous

    belercous Former Guest

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    I have a .32 S&W D/A top-break, 4th model, s/n 1064xx. The gun will work in s/a when the trigger is snapped quickly, but not when the trigger is slowly squeezed. Changeing the tension on the hammer spring doesn't help, but can make it worse (won't lock back). I've even tried adding a shim to get more tension, to no avail.
    I have seen a few of these guns for sale which state that they don't work in S/A. Is this just a design flaw or is there a fix?
    Thank you for your assistance in this matter.
  2. Jim K

    Jim K New Member

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    A better description might help, but see if this fits. You cock the hammer and it stays back. If you put light pressure on the trigger, the hammer drops, but doesn't fall all they way, catching on something. The same thing happens if you squeeze the trigger, but if you really jerk the trigger the hammer falls all the way. You might also be able to "push off" the hammer with your thumb without touching the trigger.

    If that is the situation, you probably have a hammer in which the single action notch is worn or chipped out, pretty common conditions. A gun like that needs a certain amount of finger reflex to keep the trigger out of the way of the hammer strut (the part of the hammer that the trigger bears against for double action firing. When there is not enough of a pull, the hammer falls, but the strut catches on the trigger.

    Unless you can find a new or good used hammer, there is no fix. You will simply have to treat it as a DAO revolver. A top notch gunsmith might be able to recut that notch and then re-harden the hammer, but few gunsmiths will touch those old guns, even ones of good quality, because the repairs would cost more in time than the gun is worth.

    Jim
  3. belercous

    belercous Former Guest

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    Yes, that is what it does. However, looking at the hammer (the rearmost notches which hold it back in S/A) it doesn't seem worn or chipped. Once the trigger releases from the hammer, it seems to go into double action mode. It is like the trigger mechanism doesn't pull away far enough (in the front of the hammer) to let it release fully. Nothing in the mechanism appears worn, all edges appear sharp.
  4. belercous

    belercous Former Guest

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    Oh, no, I cannot push-off the hammer when cocked.
  5. Helix_FR

    Helix_FR Active Member

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    could be that the let out on the DA sear is too much . If the let out is too much the DA sear will catch the top of the trigger when fired in SA mode. Only way to fix is replace the DA sear. You can always let them out but you can bring them back. Its not a easy fix and you need to have the parts exposed to see how it all works and unfortunately if you have never see the proper way of how they work its really hard to fix it right. Clearance from the DA sear let out to trigger is .009-.012 so its that close.
    Last edited: Dec 29, 2009
  6. belercous

    belercous Former Guest

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    I looked at Numrich, but could only find a sear, not a double-action sear. This part seems to be disengaging fine. It is up front on the hammer that seems to be catching. I can't seem to see the part (or perhaps their view does not show a side view). The part that seems to catch has a small spring forcing it rearward, onto the hammer, it catches on the part which cocks the hammer in D/A, so I see what you are calling the D/A sear.
    In S/A, when I hold the hammer back and pull the trigger, this part seems to move up a hair while the rear sear disengages, here is when it catches and goes into D/A mode.
  7. belercous

    belercous Former Guest

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    I see it now, it is part #15 on Numrich's diagram. It is shown sideways and called a front sear..
  8. belercous

    belercous Former Guest

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    In S/A I'm certain I don't have .009-.012. I don't have a set of feeler gauges in front of me, (I used to be an aircraft mechanic) and it doesn't look to be much over .002 on the front sear/hammer gap when the rear sear releases. How can I increase this gap? Should I Buy a new part (front sear) first, or can it be filed down? The hammer is case-hardened and shows no signs of wear, so I tend to belive that it is still good.
    Thank you very much Helix for your insight on this matter, I have learned something, even if I have not yet attained a complete command of the mechanism, but hopefully, I will. At least enough to fix the problem. Looks like I'll have to get a set of concave punches from Brownell's to solve this problem.
    Again, I appreciate your assistance Helix, and any other info you may be able to supply would be most appreciated.
    And please stay tuned, I may need your help again. Probably will, actually.
  9. Helix_FR

    Helix_FR Active Member

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    .009-.012 is the spec for the gap between the DA sear and the trigger cam when the hammer is down and the trigger is returned so look to that first. Try to simulate your problem and pay close attention to the DA sear and its relation to the trigger cam. (this is the top part of the trigger that makes contact with the DA sear). Im guessing by what your describing is when you pull the hammer back in SA mode and pull the trigger the hammer won't drop or if it does not very far. This is b/c the let out on the DA sear is two much or there is something buggering up the trigger and spring so the trigger is not pulling to its full rear position and the DA sear then will not clear and hits the trigger cam.

    I read your first post a couple of times and also my understanding is that if you try to shoot in DA mode the hammer will drop if you pull the trigger with intent. If you do it slowly the hammer won't drop, am I correct in saying this?

    You are 100% correct on not touching the hammer. The first rule in smithing a S&W revolver (besides making sure its not loaded) is never do anything to the hammer, work everything around the hammer.

    Shortening the DA sear may fix your SA problem but it will cause a potential timing problem in DA mode. The hammer may drop before the cylinder is in range and locked. It can also potentially create a heavy or gritty trigger. If you buy a new DA sear then it will have to be hand fit, all of them are, and I can PM some info on doing it. Its a very slow process.

    For now check the trigger function, make sure the trigger is going as far back as it can. Next slowly simulate the SA mode problem. When you cock the hammer and pull the trigger the DA sear should clear the trigger cam, I'm suspecting that its hitting it.
  10. Alpo

    Alpo Well-Known Member

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    That sounds like mine. Fire it in single action, and the hammer drops a fraction, and then catches on the trigger. As you let the trigger go forward, it lowers the hammer. Like shooting it double action, in reverse.:(
  11. Helix_FR

    Helix_FR Active Member

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    It could be a matter of stoning a slight bevel on the DA sear to clear the trigger. I'll send you some info too on it. The info I have is for the more modern Revolvers starting with the model 10 but the premise is the same. Obviously both you guys are very technically inclined, should be a no brainer for both of ya. :D
  12. belercous

    belercous Former Guest

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    Helix: I didn't know the .009-.012 was measured with the hammer down. That way its too close for me to tell by eye, looks like its close to being in range. With a slight amount of pressure on the trigger (in D/A) the hammer just begins to move and I have a gap much larger than .009-.012.
    If I pull the trigger slowly in D/A it will fire. In S/A the hammer drops, then catches and it goes into D/A. It does what Alpo's does.
    It appears that the D/A sear is not fully disengaging enough when the S/A sear disengages. It seems to be hanging up the hammer. The trigger seems to have full travel, it is not hitting the trigger gaurd.
    I thought I had it figured out and was going to work on it tonight, but I'm glad I checked here first. Now I'm not too sure what to do.
    If I put a bevel on the D/A sear I'm afraid that it might not allow the sear to cock the hammer back. I was thinking of stoning the D/A sear so that I'd have almost no gap between it and the hammer when the hammer is at rest.
  13. belercous

    belercous Former Guest

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    Could it be that the S/A sear is disengaging too early? I have to assume that the cause of this problem is a worn part, I don't think these guns would have done this when new.
    Now that I look at it with a bright light (I still haven't taken the mechanism out of the frame) I can see that the S/A sear appears worn down in the center, but this could be to provide clearance for the hammer spring. It does seem though that the hammer is still engaging the outer most parts of the sear (where it doesn't seem worn, only the center is), so maybe that's not it either. I dunno, but it just seems that something must have changed since this gun was new and all I can think of is wear.
  14. Helix_FR

    Helix_FR Active Member

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    This would be a problem with let out and a worn part can contribute to the problem. When I get home I'm going to look at the breakdown that I have on this particular model. The ones online are useless. I'll see about the SA sear. A SA sear that drops to early will also push off plus the DA sear still should not interfere.
  15. belercous

    belercous Former Guest

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    Helix: I eagerly await your reply. Thank you for your time and assistance in this matter. I have ordered some small punches from Brownell's so that I can take this thing apart. I'm real good at that. Getting it back together and having it work is another story.
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