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Thread: Saving a mint Polish parts set from a Vulcan / Hesse receiver

  1. #1
    Gunco Member cal50's Avatar
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    Default Saving a mint Polish parts set from a Vulcan / Hesse receiver

    Well I could not resist a firearm in need or in this case a matching parts set trapped not working on a Vulcan / Hesse receiver. It was a somewhat local pick up off Armslist which is REALLY a crap shoot for parts & people. In this case the guy that owned the gun was a great guy but got into this AK somehow and could not make it work.

    He purchased it as a complete gun but it never worked. Yo can see from a bottom view picture than someone welded ( badly ) on the ejector and never tried to re-contour it. That was the most obvious issue but once I got it home there were other hidden treasures. Most all of the rivets were loose and not seated. Someone used cap head screws in place of one of the rear trunnion rivets. The front receiver rivets were loose as well and spun when I used my die grinder to buzz them off. One of the lower trunnion rivets WAS tight.

    The parts set is matching with the original barrel. The only downside is someone was messing around with the bolt since the original serial numbers are barley visible and clear grinding / filing marks on it. I have a new replacement I will likely use once I start building it. It will make a nice rifle once put together correctly.

    I am on the fence on what I want to use for a receiver to build on. I can buy a new Nodak Spud NDS-1P underfolder receiver. Childers makes an excellent receiver as well.

    If anyone is another Ohio resident and has one of the above receivers they want to sell give me a shout.

    Along with the gun I receiver a new ITM receiver ( Ohio Ordnance Works ) which has a love hate relationship but it is a nice looking receiver, just not AS nice and the others listed.

    It LOOKS like and AK / As received with spare receiver~




    From the top~ Ugly ejector note the grinding dust




    I have wood~




    The original barrel is not molested, I think~



    Like new & Tight~




    What it looks like right now.....



    Bottom view ~ REALLY Fugly




    Vulcan / Hesse~ The mark of the beast


  2. #2
    Gunco Member cal50's Avatar
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    Since I learned something and most people might already know it I wanted to toss it up in this thread. Below is a reference for rear underfolder trunnion's.

    My stock assy. was correctly ID's as a Yugo and not Polish. That tip alone saved me from ordering the wrong receiver. I will go with a NDS-M92 once I line up a local FFL to receive it in for me.

    Below is a pic of three rear trunnion's for comparison:

    Note the difference between the Polish and Yugo rear trunnion's angle of the back edge. The Polish back edge is 90 degrees to the top rails, while the Yugo back edge is more than 90 degrees as it angles forward from top to bottom.




    My trunnion has an "extra" hole that should make it a Yugo M70 trunnion~




    Note hole that breaks thru the top~





    Since my rifle will be Polish & Yugo maybe its correct name is now a Pugo ?

  3. #3
    Gunco Member cal50's Avatar
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    Progress.....
    After getting ready to pull the trigger on a used Polish underfolder assy. I checked one of my favorite parts sources
    (RTG parts). They had complete & brand new Polish underfolding stock assemblies for just a tad more $99.
    IMHO it's worth it. I never had a brand new Polish stock in my hands and it is really, really nice.

    Now to line up my receiver and some new headspace gauges.
    I had a set but must have loaned them out and they never came back....


  4. #4
    Gunco Member cal50's Avatar
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    I had some free time to work on my rear stock & trunnion......

    I purchased a new rear folding stock assembly & trunnion for my project but I never knew "new" meant brand new and never fitted and assembled. Its not a big deal for me because I have equipment and a toolmaker by trade but its a tad more than I would be comfortable doing with only a drill press or dremel tool but some people are VERY resourceful.


    The rear trunnion need the large diameter center hole machined thru both sides , locking lug holes put in and a slot for the roll pin retainer. I started with the larger center hole.
    My part measured an actual .627 diameter with some taper so I bored the hole with minimal clearance for a nice fit ( I added .005" clearance ).

    The hole as received was .488" diameter so I indicated it in on center, ran a 1/2" drill thru both sides to rough it out then bored the hole to size with a boring head and carbide boring bar. The trunnion is TOUGH.

    Under size center hole and no locking lug holes~



    Boring to size~



    It fits~




    I decided to to the left side of the trunnion next.
    I measured my locking pins for size , diameter and spacing. My lugs are a different diameter so I need to machine the holes to the larger of the two diameters so its locks open and closed. Not sure if this is by design or if its an oops made in Poland.....


    The plan~



    No surprises~




    Now for the right side of the trunnion. Its spaced differently than the left side so you would not want to mix them up or you will be disappointed. The right side was a LOT harder than the left side. A sharp cobalt drill galled up quickly and did not make it thru.
    It center drilled thru fine but its really tough material. I ended up using a carbide end mill to punch a hole thru then bore to size.

    Hole bored~




    All the parts fit now~





    This trunnion would eat normal high speed steel tooling and its not something I would suggest doing unless you have the equipment and some carbide tooling.

    My measurements are from my actual parts and may not be accurate for others.
    Always check your own parts for fit & dimensions if you are machining them.

    All that's left is to machine then two small slots on the right side of the trunnion which I will have to wait becasue I am not sure what size the slots are or the dimensions. I will looks at my Nodak Spud receiver when I get it ( ordered today ) unless someone wants to share the slot width and distance.

    The chamfer for the dimples is kind of ratty and I will clean them up so they are all the same and true.
    Once that is done I will bead blast and park them along with my front trunnion and some small parts.

    Fun stuff.

  5. #5
    Gunco Member cal50's Avatar
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    Smashing stock rivets......

    If you buy a brand new Polish underfolder stock assy. you will need to do some machine work on the trunnion as mentioned above. You will also need to rivet the folding butt plate on the stock rails. These are two large rivets about .218" diameter , as mine measured. I was over thinking this part and it turned out it was WAY easier than anticipated.

    Be sure to position the folding stock rails so the cut out section of rail in on the right side of the rifle / stock as viewed from the top so it clears the safety / selector. If you put it on the wrong side you are in for a surprise when putting it on the gun.....

    I made a simple bucking bar from a milled piece of mild steel and used my Kurt 4" milling machine vice with extended vise jaws for the rivet crush. The extended jaws gave me plenty of clearance and the rivets crushed pretty easily. The .218 " diameter rivet flowed out to a .260" diameter head. I have no idea what a factory rivet head measures but these are not coming out.


    Vise , tall vise jaws and bucking bar~




    Lined up and ready to crush~






    Done~


  6. #6
    Gunco Member cal50's Avatar
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    Waiting for a few odds and ends to move forward. Ordered a electro etching stencil for the selector "C" & "P" and made a slot for the selector stop. I want to etch the receiver then blast and park the trunnion and some other small parts.

    Upon closer inspection I was not pleased with the fit of my barrel and trunnion. My trunnion was slightly ( .001" ) out of round and the press fit / barrel diameter was .0013" larger. What that means for me is I can forcible start the barrel into the trunnion and I was not happy with the fit. It might have been OK but no sense not doing it better.

    I removed the 4mm sight block base pin and rear sight base. It took an overnight soaking in Kroil and a slight touch with the smoke wrench ( torch ) and it came loose.
    I use long grade 8 bolts and turn down a stubby punch end and use it to get the pin started moving. It deformed the punch 3~4 times until it started moving. Once its moving a regular punch is used. The rear sight base also was happy where it was at and it was soaked as well and the same routine used. I did press the chamber end out instead if on the muzzle down to get it moving then pressed it out.


    Once I had everything loose I slid it forward then wrapped it with duct tape and put it in the lathe. I have a squeeze type knurling tool. Before pressing out the barrel I made a scribe line around the chamber. I stopped short of this line when I knurled so its not visible once pressed in. After the knurl was finished I increased the diameter by .0032" so my press fit should be a lot better.



    Nice knurled barrel ready to press in~





    Trunnions need your support~







    Very soon......





  7. #7
    Gunco Member cal50's Avatar
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    Just etched the receiver. I used my 12v battery jump pack for the DC power source. My solution was a 1/2 glass of really hot water with some kosher salt dissolved in it. There was extra salt on the bottom of the glass and its kosher because it was what I had in the cabinet....

    I tested my set up on a piece of flat bar stock wiped off with Naphtha. I used the "test" stencils provided. I did the 30 second burn for 4~5 cycles and got plenty of depth. Positive on the receiver / negative on the soaked patch .

    Overall I am pretty impressed with the ease and results.




    Burned on bar stock~




    The set up~




    Tape used to position stencil.
    Stencil trimmed to lie flat.




    Burned in and before clean up~





  8. #8
    Gunco Member cal50's Avatar
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    Trigger guard went on with no issues....progress.






  9. #9
    Gunco Member cal50's Avatar
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    Had some play time over the holiday weekend so worked on some tooling...

    I reworked a rivet tool I made for a 1919 Browning project for my rear trunion rivets. Basically cut the guide off and welded it on a new base plate. The punches are modified standard bolts. One for alignment of the rivet, a flat punch to seat and expand the rivet and a radius to forum the rivet head.




    I tested my dimple punch on the trunnion mag well rivet holes. Inserted a support slug between the trunnion ears and pressed both dimples for the mag well swell neck rivets. It REALLY locks in the trunnion even without rivets. The punch is another bolt with a 45 degree angle on it. My trunnion chamfers were not concentric so I cleaned them up with a chamfer tool before dumpling.

    I am waiting for an OS barrel pin from CNC warrior and I should be in the home stretch.








  10. #10
    Gunco Member cal50's Avatar
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    Riveting is fun......
    Helped a friend with his Midway Polish kit build and worked on mine as well.
    Set the front trunnion rivets and the long rear rivet, set the headspace , drilled , reamed and pinned the barrel . I am working on some long bolt cutters to try setting the rears or will try a goose neck attachment for my press.

    My matching number parts kit is now supplemented with the new bolt I used for my build. My original bolt someone was creatively grinding on and one of the bolt lugs was questionable for contact so its been replaced. It was close when I pressed the barrel back in but I set the head space then drilled and reamed for an OS pin for full contact.

    The rear trunnion and receiver was dimpled / 3 hole on each side. My rear long rivet hole needed opened up just a tad for alignment and once it was I pressed the long rear rivet.
    I will finish the remaining ones shortly.












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