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Thread: scratch build 7.62x25 on ak reciver blow back

  1. #111
    Gunco Veteran [486]'s Avatar
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    Quote Originally Posted by moleman View Post
    Surely you can post a picture of your bolt.
    Yeah, I guess I could. Well, anyways, I jumped through hoops to make it legally, I had to get my dad to fold the flat I made, as I'm 15, I did do the machining on the rest though. Made the trunnions out of aluminum, and that stuff mills like butter, especially when using a 4 flute end mill. I used a little air cutoff tool to cut the rails in the bolt, and a milsurp "4130" welding electrode [they work for nothing, though I've only ran them with an AC welder] for the firing pin. I only made a fixed extractor, so it is like a mauser in that it'll only feed from the mag.

    Pics in a few days.

  2. #112
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    Hey guys, sorry for the double post, but here are the pictures. Also a sorry to biggun, I remember him saying he was on dialup...




















    Yes, the firing pin is quite off center.

  3. #113
    gunco irregular moleman's Avatar
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    That looks pretty neat! It reminds me of the laminated bolt build but with a better solid bolt. Did the groove above the extractor solve the ejection problem? When I was researching the suomi I read accounts from soldiers who had the extractor brake, so they would fire the guns with the ejection port down. The gun would work because the case is blown back against the bolt face and the extractor was only really needed for misfires. Of course that was an open bolt gun though.

  4. #114
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    Quote Originally Posted by moleman View Post
    Did the groove above the extractor solve the ejection problem?
    I dunno, I just added it, the extractor mostly solved the problem, but they'd bounce back into the gun sometimes, so hopefully now they'll go more up than forward. I ran it with no extractor for a few rounds and it ejected straight into the chamber! It did extract though as my old trunnion took quite a beating from the bolt hitting it, the new one needs an additional bolt from under the grip to keep it from tilting like it is doing now.

  5. #115
    No Hope For Me 1biggun's Avatar
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    Interesting build. your putting a lot of faith on that rear trunion to stop the bolt. does the base of the trunion hit the bottom of it or up high after the 90? if one of those spring eyes or hooks let go look out. is the rear trunion steel or aluminum?



    My 7.62x25 reamer arrived the pilot is to big for all of my 30 cal rifles except a very old 30-30 Ill order a smaller pilot. :X

    I need the blanks to get going anyway.

  6. #116
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    Quote Originally Posted by 1biggun View Post
    Interesting build. your putting a lot of faith on that rear trunion to stop the bolt. does the base of the trunion hit the bottom of it or up high after the 90? if one of those spring eyes or hooks let go look out. is the rear trunion steel or aluminum?
    The rear trunnion is aluminum, it is starting to tilt a little, but that could be solved by putting a bolt in it to hold down the "front" of it. The hooks ain't letting go, and the springs probably won't either, but I'd know if they did, and the trunnion would probably stand up to one no spring hit...

  7. #117
    Gunco Veteran muttman's Avatar
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    486,
    nice home brew.
    I need to know how far down from the chamber hole is the front lip of the mag? this is the main " I dont know" for my build. muttman

  8. #118
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    Quote Originally Posted by muttman View Post
    486,
    nice home brew.
    I need to know how far down from the chamber hole is the front lip of the mag? this is the main " I dont know" for my build. muttman
    Well, I don't know either, you can adjust how high the mag sits and how far forward the trunnion is, and that is what I did until it looked about right. It feeds straight into the chamber when adjusted right.

  9. #119
    No Hope For Me 1biggun's Avatar
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    Ill be using a smaller than normal for a AK barrel so a feed ramp will be able to taper more into the center line of the bore. the bigger the ID of the barrel the further the ramp has to be from center of the barrel. Im thinking around 18mm with a bevel on the breach face. the trunion will have built in feed ramp. the ramp really only has be a ledge to lift the bullet up slightly. since its a pistol im trying to keep the weight down as a well no need for a heavy barrel. chinesse AK are 19 mm so Im confident a 18 mm on the smaller od lower pressure round will be OK.

    with a PPS 43 mag the bullet can move around 5/8" before the mag lips will start to let it go. since it is a double stack mag the bullet also must move from the side to the center so you cant get it to close. It looks like the mag has the bullet tip pretty well centered at around 5/8" I think that would be about were it should start entering the barrel the distance may be a little less. the lip/ledge of the guide should be just below the bullet center line. I have noticed the mag on a pps 41 seems to be angled up slightly in the front.

    what is the OD of a CZ 52 barrel BTW????

  10. #120
    Gunco Veteran Viper Dude's Avatar
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    If you fellows expect to use the PPS-43 dual position feed mags it would be well worth copying the PPS-43 breach and feed ramp specs. The barrel trunion bushing has a generous ramp to guide the .30 FMJ bottle-neck ammo. Also duplicate the PPS-43 mag positioning. A very complete parts kit with trunion/bushing, etc can provide these specs. A receiver flat or paper pattern of one can help position the mag along with the lower frame.

    VD

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