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Another metal fatigue Question

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8 comments

  • tsr1965
    perry shooter,

    What exactly broke off? The nickel plating, or the whole barrel extension, inside the frame?

    One thing that will erode steel, is chemical alterations...such as pickling for preparation for plating. But it would only alter the first few microns of the surface.

    I would suspect, in your case, the decades of corrosive ammunition, that were used in it, to be the culprit. The forcing cone should see the highest pressures, of the burning curve. With that in mind, the byproducts of black powder contain both Hydrochloric acid, and sulpheric acid. Those, in gaseous form, and under high pressure, could in fact have the effect you describe.

    Even though the exterior parts of the revolver were well cared for, the forcing cone, is about the toughest area to get surgically clean, after firing corrosive loads.

    Merry Christmas to you, my friend!

    Tim
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  • iceracerx
    Back in the 60's/70's that was called 'hydrogen embrittlement' and was common on plated hotrod parts (axles, spindles, etc).


    What you described is a classic example of 'good' steel becoming brittle after being plated.

    http://www.tau.ac.il/~chemlaba/Files/Electrodeposition/13208_02.pdf
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  • perry shooter
    Thanks guys Yes the complete Top section including the Latch still attached / ALL ONE PIECE broke off flush with the very rear of the Beginning of the barrel proper / forcing cone. The face of the break
    looked to have very large grains almost like a broken piece Of cast Iron not deformed /bent at all just a Clean break. I purchased This item from a dealer that used to appraise Guns etc on Antique Roadshow now deceased. I really like the Grip back strap to trigger distance on The S&W No 3 Target and wanted to have something Different for Cowboy Action Matches. $4000. lesson learned [:(] I still have one in 38/44 and this is blued steel but am hesitant to shoot it


    No3AMMO2_zps2d6e13d0.jpg
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  • Bill DeShivs
    If the problem was hydrogen embrittlement, it would have shown up a long time ago-when the gun was new.
    Hydrogen embrittlement on large gun parts is practically a non-issue. I have nickel plated many guns and have never seen evidence of it.
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  • v35
    It's hydrogen embrittlement from hydronium ion in acid plating bath.
    Nickel isn't the culprit.
    The hydrogen can be driven off by heating.
    I came across a S&W Russian with missing top strap and cylinder
    In Korea and wondered what it was doing there. The break was in the
    Same place. It was also plated.
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  • Bill DeShivs
    Well, that solves it, doesn't it? Two similar examples does not prove anything. There are many things more likely to cause those failures than the nickel plating. Guns have been commonly nickeled for well over 100 years. If this were a problem, it would be well known by now.
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  • v35
    It may.
    Was that an honest comment ?
    Are you an arbitrator or do you make the mistake of assuming knowledge doesn't exist beyond your own?
    Embrittlement was the subject and a likely cause.
    However, there are other metallurgical ando machine design aspects that could provide a conclusive determination.
    Failure analysis and mechanical properties of steel and iron are big subjects and your wise crack adds nothing to the discussion.
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  • machine gun moran
    When a top-break is fired, the barrel tries to rotate around the pivot. This applies downward pressure at the rear of the top strap, against its mating frame surface. The stress then moves forward along the cantilevered top strap, and is localized where the top strap meets the barrel. This micro-flexion will eventually cause metal fatigue. It will become much worse and the process will be accelerated if any looseness at all develops at the juncture of the rear of the top strap where it seats on top of the frame. Heavy-recoiling guns will suffer from this much more frequently than the small-caliber ones.
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