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Thread: Semi PKM conversion (no vendor kit)

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    Happy Camper hcpookie's Avatar
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    Default Semi PKM conversion (no vendor kit)

    I figured I'd start a new thread to focus on design specifics and semi conversion challenges.

    For now, I'm toying with a sheetmetal shell that will need considerable bending work to get right - needs the rails bent, the lower "dimple" for the feed pawl arm, and I don't have any internal rails or the "ratchet plate" for the charging handle. I may throw some money at coldsteelsolutions if I can't figure all these details and use one of his sheetmetal shells instead. Time vs. money.

    I figure I may be able to fabricate my own "ratchet plate" out of some steel tubing heated up and bent outward to the shape I need. Otherwise I'm not sure how best to go about fabricating this part.



    About the internals.

    I found a drawing of that Sig rifle I was thinking of - the STGW.57 It has a "firing lever" that the hammer strikes against. *Exactly* what I was envisioning!

    Note how the hammer - #14 - strikes against the firing lever - #11.



    This was found at the swissrifles site:

    The Stgw

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    Gunco Veteran Steelcore1964's Avatar
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    Pookie, I went ahead and started a BIY PKM thread as well, but it's over on TheAkforum.com. I have been redesigning the firing pin striker mechanism. It's been keeping me busy. I had to scrap the idea of the tension spring trolley. There was no way to attach the tension springs forward of the bolt because of interference with the bolt.
    I looked the PK receiver and carrier and screwed around with my idea. It would work but it's not something I'm crazy about. Too much fabrication and lots of small precisely made parts. On the other hand, I thought about your idea and the information you posted and went over the receiver and carrier fit for about an hour. I think your idea is the better one. Provided hammer can hit the "L" shaped transfer strut hard enough to set off the primer. I think I can modify an AK hammer to work ( if it wasn't so damn hot and humid in the garage I would be out there right now). You could keep the spur on the bottom of a full-auto AK hammer and that could interface with a modified PKM trigger group. I can see the whole thing in my head, out of battery firing could easily be prevented.
    Last edited by Steelcore1964; 05-08-2009 at 10:22 PM. Reason: better idea
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    Gunco Veteran Steelcore1964's Avatar
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    This has some nice information on it too. You can clearly see the shape and size of the hammer. You can also see the hammer strut with the coil spring as well as the hammer-strut-tubular-guide all of which would be very useful and easy to make. The coil spring and hammer strut reminds me of a Colt Python hammer spring setup.
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    Gunco Regular allesennogwat's Avatar
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    I just got a Russian PKM technical information and repair manual. (A couple of them from different years) It doesn't have a lot of dimensions but it does have rivet sizes, counter sinks and which rivet heads are suppose to be flush. It has some angles but very few measurements for the full auto fire control parts. Not very useful for semi auto but might help some layout for semi auto parts.

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    Gunco Veteran Steelcore1964's Avatar
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    Anyone know how to take apart the grip assembly on a PKM?
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    Gunco Regular allesennogwat's Avatar
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    Quote Originally Posted by Steelcore1964 View Post
    Anyone know how to take apart the grip assembly on a PKM?
    Do you mean the pistol grip? If you have the wooden one the metal piece at the top is usually pressed on the wood. Sometimes not tightly but sometimes the wood swells. The service manual shows there should be a 0.5 mm gap between the bottom outside edge of the metal and the wooden grip.

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    Gunco Veteran Steelcore1964's Avatar
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    I mean take the guts out of the trigger housing. I need the sear and trigger and all those parts to come out.
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    Gunco Veteran Steelcore1964's Avatar
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    Not too much working getting done this weekend on the PKM project with Mother's Day and all that. I did get a chance to work on it last night at about 11pm. I sawed the "ears" off of an AK hammer and about 4/5ths of the axis cylinder on one side. The modified hammer fits with plenty of clearance between the left side of the carrier and the receiver wall. I left the disconnect tab on the top of the hammer so that a modified AK disconnect can be incorporated into the design later. Looks like there is enough room in there to get this done. Pictures to follow on the hammer modification.
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    Happy Camper hcpookie's Avatar
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    I had the trigger out once to remove the sear. As I recall the detent just needs to be rotated so it will clear the housing. Mine was really REALLY gunky so you may need to clean it to see how it removes

    I'm also going to toy with some scrap on the mill today to see about making a striker plate assembly (for the firing lever). Hope to have it done by Tuesday

  10. #10
    Gunco Regular allesennogwat's Avatar
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    Quote Originally Posted by Steelcore1964 View Post
    I mean take the guts out of the trigger housing. I need the sear and trigger and all those parts to come out.
    Okay I wondered. I thought you might have meant the trigger housing.

    The operator's manual shows that better than the armorer's manual but it's not a lot of help other letting you know you have all of the parts. If I could read Russian I might be able to get more from it than just the diagrams.

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