Discussion in 'Gunsmithing and Repairs' started by Offfhand, Jan 8, 2018.
No it does not, the hammer is falling at the same rate as the trigger is moving forward. It feels like double action in reverse.
That's what I thought. I am by no means an expert on the internal working of the DA/SA trigger/hammer system. But it sounds like what (I think) is called the 'double action hammer dog', is catching on the DA sear of the trigger as the hammer releases.
How that could be happening, I don't know. If it were me, I'd disassemble the gun and take a look. But that's a decision you should make for yourself. Whether to send it to S&W versus a local smith is hard to say. It could just be something sticking, or a part could be broken or worn and need replacing.
If the hammer and trigger are still free to return without binding, @WrongHanded, might be right, though I think he's mixing up the locations of the sear, etc.
Check out the pic below. What I think @WrongHanded is suggesting is that the hammer's DA sear is catching on the trigger nose as the hammer's falling, which might be caused by a DA sear that's too long.
What's confusing to me is why it "sometimes" does it. Maybe a worn/cracked hammer or trigger pin? That'd definitely be a trip to S&W.
If this (sear/nose interaction) is what's going on, I'm also confused on why DA function would be unaffected. Seems to me if the DA sear were this long, it'd hit the trigger nose after the hammer starts coming down as well, though I'd actually have to have an opened gun in front of me to look at clearances, etc.
If the hammer and trigger bind up rather than freely returning, I tend to think the SA sear is binding against the trigger cam as the hammer's falling. I just described that in a recent thread as a faux half-cock, something S&W's are definitely not engineered to do.
Yes, I have very little knowledge of terminology in this department. I pretty much take things apart and see how they work, whilst shamefully never learning the correct names of parts. Part 'A' is what I was thinking of. Some company that makes various shims had an arrow pointed to that part and referred to it as the "Double Action Hammer Dog". But if DA sear is the correct terminology, I'll try to remember that.
I was thinking on the 'why' of the problem earlier. If it is the DA sear that is catching on the trigger nose, perhaps the retaining pin for the DA sear is bent or half way out (as MrBorland said), so that sometimes it sits farther forward than it should. That might allow it to catch in SA, but move up and away in DA. Which might result in the DA pull being shorter than it used to be.
Or it could be something else entirely.
So what WAS the cause?
Uh, oh! Bad juju!
Sure startles you when that happens, don't it? Not used to getting kicked in the finger upon the shot! Wrong angle or excessive length on the hammer dog. Pretty simple fix, but most of the major OEM's make them come home for it. I pick up spare hammers and other lockwork for common revolvers when I can find them, so I generally just swap them around. Can be cut from barstock too, but it takes more time than it's worth most of the time.
If you're getting shoved by the trigger when the hammer falls from SA, and the hammer stops, the only failure mode is an over length or over angle hammer dog (DA sear). There's not enough mechanical "time" between the DA sear and the SA sear break for the DA sear to clear.
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