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  1. #1
    Tinhorn
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    39A fail to fire about 40% of the time

    I acquired a beat up pre-1974 39A that I'm trying to fix up. It came without a firing pin, so I bought the correct one from Brownells. The bolt and firing pin were properly lubricated. Initial test fire revealed about 40% fail to fire on the initial hammer fall in spite of healthy looking dents on the case rim. The ammo (Federal 550 bulk) ignited fine in my 1911 conversion kit. I had a spare (used) mainspring so I replaced the one it came with to my spare. My spare was slightly shorter than the original. The spare will ignite anything in my other 39A. I just test fired the gun with the known spare mainspring and it's still at about 40% ignition on the first hammer fall. I'm unsure where to go from here...a new mainspring? Perhaps a spacer I can add behind the mainspring to effectively shorten it's compressed length?

  2. #2
    Army Veteran 67-69 Korea Administrator
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    Re: 39A fail to fire about 40% of the time

    To start with it came without a firing pin, so there was a problem there at one time.

    Check the channel the pin fits into for burrs ect that may slow it down. Check the new pin also for any burrs that ride in the channel, stone them if so. I have had one that had a slight bend in it and caused mis fires, after straightening and stoning smooth it works well.

    Add two #10 machine washers to the rear of the mainspring to add preload pressure which increased hammer strike.

    The third thing would be to modify the pin itself, I know it's new but they come with a step in them the outer one hits the rim and causes the ignition, the inner one stops it from hitting too hard. If yours it just a few thousandths off it will cause a misfire. I will post a picture but make sure you take matierial off the lower side that does not strike the rim allowing it to strike deeper with more force.

    Go through the steps to correct the problem one at a time, I can only surmise what is the problem from here, sometimes a simple stoning or the washers do wonders. Hope you do well, I shoot fed bulk in my 39A and 39AS and have no problems now, but had failure to fire or extract in both at one time in the past and have done all I advised you.
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    God Bless Our Troops -- Retired Tool & Die Maker -- The center of an Aspirin is the same size as the center of the moon, aim for the center.

  3. #3
    Tinhorn
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    Re: 39A fail to fire about 40% of the time

    Quote Originally Posted by swany
    To start with it came without a firing pin, so there was a problem there at one time.

    Check the channel the pin fits into for burrs ect that may slow it down. Check the new pin also for any burrs that ride in the channel, stone them if so. I have had one that had a slight bend in it and caused mis fires, after straightening and stoning smooth it works well.

    Add two #10 machine washers to the rear of the mainspring to add preload pressure which increased hammer strike.

    The third thing would be to modify the pin itself, I know it's new but they come with a step in them the outer one hits the rim and causes the ignition, the inner one stops it from hitting too hard. If yours it just a few thousandths off it will cause a misfire. I will post a picture but make sure you take matierial off the lower side that does not strike the rim allowing it to strike deeper with more force.

    Go through the steps to correct the problem one at a time, I can only surmise what is the problem from here, sometimes a simple stoning or the washers do wonders. Hope you do well, I shoot fed bulk in my 39A and 39AS and have no problems now, but had failure to fire or extract in both at one time in the past and have done all I advised you.
    Thanks! I'll report back on my results...

  4. #4
    Tinhorn
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    Re: 39A fail to fire about 40% of the time

    swany,

    You're right, the FP needs to be modified, in fact I don't like the FP at all because it has a bevel on the North side of it, whereas my other 39A has more material sticking out there to hit the rim of the cartridge stronger.

  5. #5
    Army Veteran 67-69 Korea Administrator
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    Re: 39A fail to fire about 40% of the time

    Fix it and give us a report. Sometimes getting to know your gun is what is needed.
    God Bless Our Troops -- Retired Tool & Die Maker -- The center of an Aspirin is the same size as the center of the moon, aim for the center.

  6. #6
    Tinhorn
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    Re: 39A fail to fire about 40% of the time

    Quote Originally Posted by swany
    Check the channel the pin fits into for burrs ect that may slow it down. Check the new pin also for any burrs that ride in the channel, stone them if so. I have had one that had a slight bend in it and caused mis fires, after straightening and stoning smooth it works well.

    Add two #10 machine washers to the rear of the mainspring to add preload pressure which increased hammer strike.

    The third thing would be to modify the pin itself, I know it's new but they come with a step in them the outer one hits the rim and causes the ignition, the inner one stops it from hitting too hard. If yours it just a few thousandths off it will cause a misfire. I will post a picture but make sure you take matierial off the lower side that does not strike the rim allowing it to strike deeper with more force.
    The FP is straight and there's no burrs. I added two #10 washers, the gun lit 'em off more often. I then modified the FP tip per your instructions and ignition is better, but I'm still only up to about 70%. Does anyone have any advice?

    Thanks,
    Bill

  7. #7
    Marlin Marksman
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    Re: 39A fail to fire about 40% of the time

    Remove the extractor and see if ignition improves. If it does, attend to the fit of the extractor. If it's the same then we move on.~Andrew

  8. #8
    Tinhorn
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    Re: 39A fail to fire about 40% of the time

    Quote Originally Posted by Andrew
    Remove the extractor and see if ignition improves. If it does, attend to the fit of the extractor. If it's the same then we move on.~Andrew
    Same ignition rate (70-80%) with the extractor removed.

    While messing with the bolt I noticed the FP doesn't have much travel, so I'm going to compare the FP length with my other 39A and see if there's a significant difference.

  9. #9
    Gun Wizard
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    Re: 39A fail to fire about 40% of the time

    Degrease the firing pin to remove all lubrication. If it works after that, then maybe a bit more stoning is in order and very little and very light oiling or dry graphite, maybe? We don't have oil congealing problems in PR.
    Speak softly, but ride like hell!"

  10. #10
    Army Veteran 67-69 Korea Administrator
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    Re: 39A fail to fire about 40% of the time

    You likely should tear it down and spend a lot of time with small picks like dental picks and check for carbon build up in the chamber area. Check for any indents in the chamber where the firing pin strikes (maybe it had be dry fired a lot)

    Get the new main spring, and polish and smooth the rod the spring rides on. In your inspection check everything to do with the ignition system, from the mainspring retainer fwd, includes mainspring, the rod it rides on, the hammers pivot pin, the area the hammer strikes the bolt. On mine the firing pin was bent and I flattened then stoned it until it would go back and forth just by shaking the bolt. That cured all my failure to fire in that 39A.
    God Bless Our Troops -- Retired Tool & Die Maker -- The center of an Aspirin is the same size as the center of the moon, aim for the center.


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