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Smith K38 Misfires w/ Single Action Kit

MG1890MG1890 Member Posts: 4,649
edited April 2015 in Ask the Experts
I pulled out the regular hammer and trigger and installed brand new single action only hammer and trigger. Used the original mainspring.

Now the hammer has much less force than normal. Strain screw is all the way in. Do these hammers require a special mainspring??

Won't hit hard enough to fire... nice dent, but no cigar..

Also, hammer wanted to bind in frame unless I left the sideplate screws a little loose... It's not binding now, and shouldn't these parts be "drop in"???


OK, I am listening so far..... Boy, I sure hate to start polishing on the hammer width, that beautiful case coloring.

So far nobody has commented on the actual mainspring application for single action only guns, if they are the same as standard SA/DA guns.

Comments

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    rufe-snowrufe-snow Member Posts: 18,650 ✭✭✭
    edited November -1
    If your using handloads, use Federal primers. I've had similar problems with striker fired automatics. The use of Federal primers, has resolved the problem.

    The brass colored Winchester primers, and the Russian made Wolf primers. Caused the majority of the ignition problems.
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    Laredo LeftyLaredo Lefty Member Posts: 13,451 ✭✭✭
    edited November -1
    If the gun is working right it should fire consistently with all primers. If the hammer was binding against the side plate, I would suggest having a good gunsmith take a look at it. It might just need to be fitted and adjusted.
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    charliemeyer007charliemeyer007 Member Posts: 6,579 ✭✭✭
    edited November -1
    When you are looking at match grade I don't think "drop in" applies you are looking at "fitted" IMHO.

    How does the nose fit in the frame? You de-burred the new parts? Checked the thickness of new to old parts?

    Are we talking a K-38 or a later Model 15?-something.

    Added: The last one I remember seeing was in the mid 70's and I think it was a factory option. I would get a new main spring and modify the arch to get more strike. I would make sure there are no burrs on the hammer. Candle soot for fitting provides more clearance than sharpie black. You need to figure out where on the hammer it binds when the screws are tight. Could be just the thickness at the hammer stud, or on the side plate. Fitting a part is a hands on job.

    Added2 I would rather radius the hole in the hammer on the stud frame side than cut the stud at a 90 degree. It is easier and less of a stress concentrator on the parts.
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    v35v35 Member Posts: 12,710 ✭✭✭
    edited November -1
    If the firing pin centers the recoil hole exactly and protrudes .050-.060 then get/ make a longer hammer spring tensioning screw,
    test for proper indentation and shorten to make screw head flush with frame.
    Don't mess with primer selection as the result will only be marginal.
    You obviously have the mainspring upper yoke binding on the hammer
    spring clearance curvature. If that is the case, metal needs to be removed on either part where binding occurs.
    On the other hand if binding occurs with sideplate tight and not when loose, that's another issue.Assuming the hammer pivot pin isn't loose, the hammer width is too wide for the gun.If that's the case metal needs to be removed judiciously from each side of the hammer so as to allow the firing pin to center in the hole.
    Always alter the cheapest part should you FIU. Not the gun frame or sideplate.
    I would not operate that gun with a loose sideplate.
    Note S&W parts are case hardened and you will break through the case.
    Measure width of both hammers before removing any metal.
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    dfletcherdfletcher Member Posts: 8,164 ✭✭✭
    edited November -1
    quote:Originally posted by MG1890
    I pulled out the regular hammer and trigger and installed brand new single action only hammer and trigger. Used the original mainspring.

    Now the hammer has much less force than normal. Strain screw is all the way in. Do these hammers require a special mainspring??

    Won't hit hard enough to fire... nice dent, but no cigar..

    Also, hammer wanted to bind in frame unless I left the sideplate screws a little loose... It's not binding now, and shouldn't these parts be "drop in"???


    OK, I am listening so far..... Boy, I sure hate to start polishing on the hammer width, that beautiful case coloring.

    So far nobody has commented on the actual mainspring application for single action only guns, if they are the same as standard SA/DA guns.


    I know about the SA hammer, wasn't aware there's a SA trigger - what's the difference between DA trigger & SA trigger?

    If hammer fall force is marginal it would tend to show misfires in DA mode, SA mode is a bit longer and should pack more punch. Is binding slowing down hammer fall? Did the gun misfire before? Are you sure the original mainspring screw was full length? Sometimes folks shorten them for a lighter pull.

    Regarding binding, there are fixes depending on the cause. Is it binding to the sideplate side or frame side? Does the hammer have "wiggle room" at rest or full cock? If binding to the frame side, you can shim between hammer & frame on the hammer post, that will move the hammer to the right. Or, you could slightly dress down the inside sideplate where the hammer rides, you'll see a round polished area around the hole where the hammer post sits in the sideplate. This is a "be very careful" operation.

    You could shim under the sideplate screws just a tad, raising the plate out a bit, but the sideplate might show a little proud.

    A trick for getting a stronger mainspring - slip an expended large primer with anvil removed over the "stud" end of the strain screw. It gives a little extra tension and stays put.

    I wouldn't describe outfitting a Smith with a new hammer and trigger as "drop in" (unless comparing it to a Colt ...[;)]) but rather requiring a bit of work, or good luck. Does the cylinder bolt drop before the cylinder starts moving, drops on time, lock up is OK?

    As an aside, once you get your mainspring situation corrected don't be surprised if trigger return is a bit soft. A stronger mainspring imparts more resistance on the returning trigger rebound unit. An 11 lb trigger rebound spring is fairly light, a 15 lb will pretty much always work.
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    iceracerxiceracerx Member Posts: 8,860 ✭✭✭
    edited November -1
    +1

    Federal primers should be the fix.


    quote:Originally posted by rufe-snow
    If your using handloads, use Federal primers. I've had similar problems with striker fired automatics. The use of Federal primers, has resolved the problem.

    The brass colored Winchester primers, and the Russian made Wolf primers. Caused the majority of the ignition problems.
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    MG1890MG1890 Member Posts: 4,649
    edited November -1
    It fired fine with all brands of primers before the single action only parts; the hammer is noticeably weak.

    I want to fix the gun.
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    chris8X57chris8X57 Member Posts: 1,249 ✭✭✭✭
    edited November -1
    I think that you noted the problem.. that the hammer binds with the side plate tightened.

    Hammers from S&W are not dimensionally consistent, and you are getting drag after tightening the side plate, and a free pivot with it loosened.

    The hammer stud often has a small fillet or radius at the base of stud where it meets the pad. We used to use a cutter that had a clearance hole for the stud that cut the pad flat to achieve hammer clearance and allow the hammer to pivot freely.

    Do not file the hammer pad on the side plate, as S&W usually has done this to a minimum clearance.

    We never once sanded or reduced the side of the hammer itself to achieve a proper fit - always it was done to the pads themselves. The case hardening on the hammer is not only aesthetic, it has a function.

    I doubt that a longer strain screw will help, as you had adequate ignition with the original hammer, so mainspring tension is not an issue here.
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    v35v35 Member Posts: 12,710 ✭✭✭
    edited November -1
    If you screw with frame spacers then when reverting back to DA hammer the hammer will abrade on the frame and chafe the hammer case hardening off. To avoid that, shims would need to be made to space the sides of the original hammer away from the frame & sideplate.
    If you measure width of both hammers you will see how much metal needs to be removed either from frame or SA hammer. Again, modify the cheaper part.
    As case hardening on wear surfaces has function, case color hardening on hammer sides has no function except appearance.
    As it appears too long an explanation is confusing to you , it might be better for a good pistolsmith do the job.
    The S&W sideplates are tapered and fit into a tapered frame cutout, shooting with the sideplate loose or spaced out is not a good idea.
    Once you loosen the hammer pin from the frame it's not a nice fix to remount it.
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    MG1890MG1890 Member Posts: 4,649
    edited November -1
    Got it fixed. Put some blue ink on the hammer, found where it was making contact with the side plate. Carefully relieved the side plate with a single cut file until it stopped binding.

    Thanks to all for your help!
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    Bill DeShivsBill DeShivs Member Posts: 1,264 ✭✭✭
    edited November -1
    You should have relieved the hammer. It can be replaced. The sideplate can't.
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    MG1890MG1890 Member Posts: 4,649
    edited November -1
    Sideplate had already been replaced.
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