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Material for new firing pin? FN Trombone

Discussion in 'Gunsmithing and Repairs' started by Badger Arms, Oct 14, 2015.

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  1. Badger Arms

    Badger Arms Member

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    I have an FN Trombone rifle that I recently acquired. The firing pin is pretty beat up on it and looks like it might have been either fabricated as a replacement or poorly repaired. From reading the internet, it seems pretty common that these break, but replacements are $50 or more if you can find them. It's a super-simple design and I can make one in about half an hour, but I don't know what kind of material to use.

    So, the question is, what type of material should I use and what type of heat treating would be recommended? I need something I can heat treat at home, preferably. The fabrication isn't a big deal. I plan on making it from 1/8" plate stock of whatever I end up getting. I haven't test fired the gun, but I want a replacement firing pin no matter what way I go.

    It's a flat steel part, like the Ruger 10/22 one, but thicker. Here's a picture from the IPB:

    22147290056_fe83cc99e1_b.jpg
     
  2. rcmodel

    rcmodel Member in memoriam

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    I'd get a chunk of O1 tool steel.

    http://www.knifemaking.com/category-s/267.htm

    It is easy to work, and easily oil hardened and drawn with a torch.

    To harden, heat red hot and quench in warm oil.

    To draw the temper for a firing pin, polish it so you can see the color change.
    Then reheat till it turns a uniform straw on the body, to dark blue color at the tip.

    rc
     
    Last edited: Oct 14, 2015
  3. Kp321

    Kp321 Member

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    I keep an old circle saw blade to make flat firing pins from. The metal is tough but can be worked with a good file. No further heat treatment needed.
    Use an old non-carbide tipped blade. The carbide tipped blades are not as good a steel.
     
  4. Badger Arms

    Badger Arms Member

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    THANKS! I've got some experience heat treating aluminum, but not steel. Is there a way to ensure that the striking faces on the ends are harder and the interior more ductile? I assume that I'll just be letting it cool after it turns blue? If I heat it more in the center, would that work for my purposes? All I have is a propane torch, but I think that should handle it.
     
  5. rcmodel

    rcmodel Member in memoriam

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    No, you can't differently temper O1 with a torch on something that small.

    Old saw blades can work.

    New saw blades today are mystery metal, and are as often to be air hardening steel as anything you can temper yourself with fire & oil.

    It's a crap shoot at best to put all that work into an unknown steel you have no idea how to heat treat.

    If you can cut it, file it, and not get it too hot, it might work though.

    rc
     
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