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Thread: Semi PKM conversion (no vendor kit)

  1. #21
    Gunco Veteran Steelcore1964's Avatar
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    This is how I am making the dual mainspring keepers, these will get welded to a thin plate of 4130 which will mount on the back of the carrier.The two cut AK spring retainers have gotten welded on to a plate that attaches to the back of the carrier. They are angled out to lay into the bottom corrners of the receiver and will recess into two holes in the stock. This provides more than enough room for the hammer to work just like an AK hammer but the hammer will need to be just a little taller.
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    Last edited by Steelcore1964; 05-25-2009 at 08:58 PM.
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  2. #22
    Gunco Veteran Steelcore1964's Avatar
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    Quote Originally Posted by hcpookie View Post
    Steelcore, did you get a chance to see if the AR hammer fits with more room?
    Not yet but I think it might work better
    That which does not kill you, makes you stronger

  3. #23
    Happy Camper hcpookie's Avatar
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    LMK if you need a part and I'll machine it for you
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  4. #24
    Gunco Regular allesennogwat's Avatar
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    Quote Originally Posted by Steelcore1964 View Post
    Can you post the rivet information, that would help a lot.
    I can copy the rivet sizes. It gives rivet diameter, length and rivet head size and which ones are swell head rivets. The locations will be difficult as it's all in Russian but I may be able to post the pics of how they are suppose to be. Copying the numbers and how many of each size and kind of rivets looks doable, it will just take a bit of time to copy and post the info.

  5. #25
    Gunco Veteran Steelcore1964's Avatar
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    Quote Originally Posted by allesennogwat View Post
    I can copy the rivet sizes. It gives rivet diameter, length and rivet head size and which ones are swell head rivets. The locations will be difficult as it's all in Russian but I may be able to post the pics of how they are suppose to be. Copying the numbers and how many of each size and kind of rivets looks doable, it will just take a bit of time to copy and post the info.
    I work with people from Russia and they said they would translate for me.
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  6. #26
    Gunco Veteran Steelcore1964's Avatar
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    Quote Originally Posted by hcpookie View Post
    LMK if you need a part and I'll machine it for you
    Thanks Jerry, I will need two spring "buckets" that AK recoil spring barely fit in. They need to be about 4" long and very thin walled. I paln on going to Lowes later to find some kind of tubing, Im thinking 1/2" conduit turned down to a thinner wall it will also need a small lip on one end.
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  7. #27
    Gunco Regular allesennogwat's Avatar
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    PKM rivets

    It looks like only the long rivets are swell head rivets.

    The flat head rivets have a counter sink under the head similar to a swell head rivet. The counter sink is shown as "90 degrees" which is in American measures would be 45 degrees from center. The flat rivets are the ones that fit flush in their locations.

    .............................

    Long rivets (swell head)

    shank diameter = 5.0 mm

    swell head is 1.5 mm high / long at 45 degrees from center

    round head of swell head long rivets is 2.0 mm high past swell angle, radius is unknown at this time, round head diameter is 8.0 mm (+0.5 / -0.2), length of rivet from swell head - round head parting line to other end is 53.0 mm , round head adds 2.0 mm, usually radius of round head is shown but I don't see it for the long rivets. Round head is 8.0 mm diameter and 2.0 mm high. The aprox length of rivet after fitting to PKM is 40.0 mm

    ,,,,,,,,,,,,,,,,,,,,,,,,,,

    The short round head rivets have no swell necks.

    Lengths do not include round head.

    Rivet 1 is 10.0 mm long, 8.0 mm diameter head, 5.0 mm diameter shank, head radius is 4.2 mm, head height is 3.0 mm

    ,,,,,,,,,,,,,,,,,,,,,,

    Rivet 2 is 12.0 mm long, head dia = 8.5 mm, shank dia = 5.5 mm, head radius = 4.2 mm, head height = 2.5 mm

    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

    Rivet 3 is 12.0 mm long, head dia = 8.0 mm, shank dia = 5.0 mm, head radius = 4.2 mm , head height = 2.5 mm

    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

    Rivet 4 is 8.5 mm long, head dia = 8.0 mm , shank dia = 5.0 mm , head radius = 4.2 mm , head height = 3.0 mm

    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

    Rivet 5 is 10.5 mm long, head dia = 7.1 mm, shank dia = 4.0 mm, head radius = 3.8 mm , head height = 2.4 mm


    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

    Rivet 6 is 5.5 mm long, head dia = 5.3 mm , shank dia = 3.3 mm , head radius = 2.9 mm , head height = 1.8 mm


    That was the plain round head rivets.


    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,


    Flat head with counter sink / swell rivets

    Flathead rivet 1 is 11.0 mm long including the head, 45 degree counter sink swell is 2.5 mm long, hed dia = 10.0 mm , shank dia = 5.0 mm

    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

    Flathead rivet 2 is 9.0 mm long including head, 45 degree swell is 2.5 mm long, head dia = 10.0 mm , shank dia = 5.0 mm

    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

    Flathead rivet 3 is 6.0 mm (+1.0 mm) long including head, 45 swell is 1.5 mm long, head dia = 6.0 mm , shank dia = 3.0 mm

    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,


    Flathead rivet 4 is 9.0 mm long including head, 45 degree swell is 1.8 mm long, head dia = 7.6 mm , shank dia = 4.0 mm

    That's the flat head rivets with counter sink.

    ,,,,,,,,,,,,,,,,,,,,,,

  8. #28
    Gunco Veteran Steelcore1964's Avatar
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    The next step is to mock up a new stock so that I can build a jig to drill the spring holes in the stock. The mock-up will be just a block of wood about 5 inches long and the same inner and outer dimensions as the stock. I will only get one chance to drill my real Russian PKM stock.
    That which does not kill you, makes you stronger

  9. #29
    Happy Camper hcpookie's Avatar
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    hey look at me 5000 posts!


    Alright. Thinking more about the dual-spring setup, I got my receiver shell out and toyed around some.


    I think the dual-spring setup will work BETTER than my Swiss-style striker-plate.

    If dual-springs are used, they will have some MAJOR problems to overcome. Namely, there is not enough space to compress an AK-style recoil spring before it bunches up and prevents the backward motion of the carrier.

    I think I figured a way around that.

    Looking closely at some of my pistols, there is a spring oprod design that uses two tubes one nested in the other, and two springs - a smaller spring nested on the smaller tube, and a larger spring around both the larger tube AND the small spring. Both springs work together and move about halfway each - the oprod (recoil rod?) moves completely back. A very clever design!

    Based on that dual-spring setup, I mocked up this conceptual in Visio:






    This design would let both pieces of spring be shorter than the overall travel, and yet should provide enough travel to let the recoil cycle completely.

    I discovered that a VZ-58 striker spring and an AK recoil spring should work together in this design. I can lathe up some tubing and a section of steel rod the guide rod pieces. The smaller spring will require an 11/64" size guide rod. 3/16" won't do it. I may get some drill rod as I've had problems finding this size of rod before. I don't know if the VZ guide rod is available, but if so that would work as-is.

    There is perhaps 1/2" or so that can be cut from the bottom corners of the buttstock so that the springs have a bit more room to compress. Any further and you'd expose the spring.



    SO.

    This should give us some room to use an AK-style action, although the hammer will need to be longer. Perhaps a FAL-style action could work? US-built FAL parts are available and that would be three US parts right there.


    Build update -

    I received my plate steel in the mail so I can make a bending jig of sorts for the upper rails! Hopefully this weekend I can get some rails bent!

    I still need to figure the best way to bend that "spine" on the rails. Seems like I'll need to bend the rails OUT to about 90 degrees, then place a wedge of some sort inside so that I can bend the rails all the way in. I am concerned that my receiver shell doesn't have enough metal to make the "spine", so I may abandon it.

    After looking at some more close-up pics of the receiver, the "spine" on the outside of the rails is not always present - seems some countries or perhaps newer models don't put that extra work into the receiver. Maybe I'll just bend them like AK rails and be done with it.
    Gunco Member #10

    http://pookieweb.net


    The "original" Boltcutter Rivet Squeezers:
    http://pookieweb.net/AK/rivet/boltcutters/boltcutter.htm


    Project Pink - the Pink and Blue AK-74:
    http://pookieweb.net/pink/pink.htm

  10. #30
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    Quote Originally Posted by hcpookie View Post

    If dual-springs are used, they will have some MAJOR problems to overcome. Namely, there is not enough space to compress an AK-style recoil spring before it bunches up and prevents the backward motion of the carrier.


    This should give us some room to use an AK-style action, although the hammer will need to be longer. Perhaps a FAL-style action could work? US-built FAL parts are available and that would be three US parts right there.
    I have the same problem with a .45acp carbine, at first I cut the double hook trigger down to a single hook, and cut the unused sear surface off of the hammer, and most of the other one, mostly to reduce locktime... Then I started thinking, and then thought that the dual recoil springs would be a good idea, so then I came up with using unmodified AR15 HTS set, the FAL parts are more expensive and use a plunger type hammer spring, they would be harder to use, so I'm gonna use the AR HTS...

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