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Thread: Another 7.62x25

  1. #1
    Gunco Rookie rk5n's Avatar
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    Default Another 7.62x25

    First of all, BIG thanks to rahatlakhoom for doing the welding I couldn't do with my buddy's 90 amp mig. Also thanks goes to anyone else who has built one (I did a LOT of research).

    This is my 3rd gun (also have a Saiga 223 and a Remington 11-48 12ga) and my first build. I come from a hobbyist machining background, that experience made this build a lot easier than it would have been. I started with a AMD-65 barrelless kit and a PPsh 16" barrel. I'll list the highlights that set it apart from others.
    -The receiver was shortened nearly an inch and a quarter.
    -The top cover is hinged at the rear sight block so the rear sight can maintain a zero.
    -The front sight was welded to the gas block at 3/8" over the standard height to align with the HK rear.
    -The barrel had to be sleeved in 3 places to fit the trunnion, hg retainer and FSB.
    -Mag catches were welded to PPs-43 magazines to fit in an aluminum internal magwell.

    It was running at about 85% efficiency with S&B ammo. But now I got a case of polish surplus and the firing pin isn't puncturing the hard primers. I reworked it a bit and it should be working better now.
    The main problem I've been having is that sometimes it will short stroke, not resetting the hammer (NOT hammer follow) or ejecting the cartridge. Its quite puzzling since when it works, it has a nice crisp kick. When it short strokes, the kick is very weak. I think more polishing and filing of the rails would fix the short stroking.







  2. #2
    TRX
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    Niiice! I like the Krinkov-style top cover.

    Are you using the standard-length recoil spring or did you cut one down? You might have too much spring for it to cycle reliably. If necessary, you can wind a replacement from thinner music wire wrapped around a dowel.

    Are you sure the hole in the gas block is properly aligned with the one in the barrel?

    Is the gas piston going far enough up into the gas block? As long as it's not bottoming out inside the block, you might try fitting a washer between the back of the piston and the bolt carrier. The longer stroke would provide more kick to the carrier.

    How far back does the bolt carrier travel when it's working correctly? A small chunk of modeling clay on the buffer will tell you. Don't use too much; you don't want to bottom the carrier out on the clay.

    Do you have access to any other ammo? You might have a bad batch, or some that's mixed from more than one batch.

    I don't know if it's a valid test, but I removed the hammer and recoil spring from my AKM while I was fitting the side rails, and decided they were good enough when I could point the muzzle down, let go of the bolt carrier, and the rifle would go into battery with no urging. My ejector was binding the bolt when I started, and it took a little grinding to get everything to clear properly.

  3. #3
    No Hope For Me Coils's Avatar
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    Nice build, really nice. Thanks for the pics too.

    -Mag catches were welded to PPs-43 magazines to fit in an aluminum internal magwell.
    That's a great idea.

    How is the bolt setup in the carrier, is it fixed or can it be removed yet?
    "Government is not the solution to our problem, government is the problem" Ronald Reagan

  4. #4
    Gunco Rookie rk5n's Avatar
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    Quote Originally Posted by TRX View Post
    Are you using the standard-length recoil spring or did you cut one down? You might have too much spring for it to cycle reliably.
    Are you sure the hole in the gas block is properly aligned with the one in the barrel?
    Is the gas piston going far enough up into the gas block? As long as it's not bottoming out inside the block, you might try fitting a washer between the back of the piston and the bolt carrier. The longer stroke would provide more kick to the carrier.
    How far back does the bolt carrier travel when it's working correctly? A small chunk of modeling clay on the buffer will tell you. Don't use too much; you don't want to bottom the carrier out on the clay.
    Do you have access to any other ammo? You might have a bad batch, or some that's mixed from more than one batch.
    I don't know if it's a valid test, but I removed the hammer and recoil spring from my AKM while I was fitting the side rails, and decided they were good enough when I could point the muzzle down, let go of the bolt carrier, and the rifle would go into battery with no urging. My ejector was binding the bolt when I started, and it took a little grinding to get everything to clear properly.
    Sorry I didn't put this in the first post, but its blowback, not gas operated. The piston is there only to provide a guide for the bolt carrier. I'm still using the standard recoil spring, maybe one day I'll cut a couple inches off. The carrier recoils all the way back to the buffer, I can tell from the marks on it. The plastic piece behind the buffer is just a spacer so the bolt doesn't travel past the hammer and get hung up.
    That test you mentioned for the smoothness of the action sounds good, I'll have to try it.

    Quote Originally Posted by Coils View Post
    How is the bolt setup in the carrier, is it fixed or can it be removed yet?
    Thanks, the bolt can be rotated out of the carrier the opposite way a standard ak bolt is removed. I have a set screw in the carrier to hold it in place but I found that its not needed.

  5. #5
    No Hope For Me 1biggun's Avatar
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    Sorry I didn't put this in the first post, but its blowback,
    that is what I guessed by looking at the bolt in the carrier. Nice looking build did you take any pre assembly pictures of the barrel, trunion , mags etc

    I lke the build a lot. some close up pics of the mag lugs and the internal mag well would be apreaciated. I was thinking of just welding lugs to my mags as well. does your mag hookin the front like a Normal AK or is it only held by the rear release and just slid up into a mag well??

    some close ups of the carrier and bolt mods would be nice.

    to check carrier travel just put some thin strips of tape over the slot were the charge handel travels space the tape every 1/4" apart and were the handel stops tearing them off is the amount of travel.

  6. #6
    Gunco Rookie rk5n's Avatar
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    Quote Originally Posted by 1biggun View Post
    that is what I guessed by looking at the bolt in the carrier. Nice looking build did you take any pre assembly pictures of the barrel, trunion , mags etc

    I lke the build a lot. some close up pics of the mag lugs and the internal mag well would be apreaciated. I was thinking of just welding lugs to my mags as well. does your mag hookin the front like a Normal AK or is it only held by the rear release and just slid up into a mag well??

    some close ups of the carrier and bolt mods would be nice.

    to check carrier travel just put some thin strips of tape over the slot were the charge handel travels space the tape every 1/4" apart and were the handel stops tearing them off is the amount of travel.

    Sorry it took so long to reply, but here is the only picture I have of the build right now. My computer died a few weeks ago so I lost everything. Hopefully I'll be able to get all the pictures back soon. Anyway, the picture shows the two aluminum plates that go on either side of the magazine. They're a little oversized since the magazines vary in width (I only have three magazines currently, only two have tabs but all are different widths). Not pictured is the bullet guide/forward part of the magazine well. Its also aluminum and goes up tight against the front of the magazine. The magazine is held in by the rear tab and the tightness of the magazine well.

    The bolt carrier does recoil back all the way, it just doesn't do it all the time. There has to be a burr or something on the underside of the receiver rails I'm overlooking. I haven't had much time to look (college student).

    I have some questions regarding heat treating. Since I did a lot of grinding on the major parts of the gun, I'm thinking I should go back and heat treat the necessities before they deform any more than they have. One area I have noticed slight deformations is the rear of the bolt since that is what pushes the hammer back upon recoil. It created a burr that made it pretty hard to remove the firing pin. Thats also a concern of mine, the firing pin since I ground down both sides. The third potential problem area is the carrier stop. I took about 3/8" off the carrier here when I was setting the headspace but made sure to leave the trunnion carrier stop unmodified.

    So that brings me to the questions. I know the rear of the bolt has to be hardened. I think I'll be ok to just heat that area and not the whole bolt so as to not mess up the welds on the face. I also think that spot heat treating the carrier where it hits the trunnion would be better than doing the whole thing. Next, the firing pin. Should I heat treat the whole thing? I did a search through google and ended up with a bunch of conflicting information. Some say only the primer end needs to be heat treated, some say only the hammer end. Some say tempering to blue or straw is better, some say that drawing at 400* for an hour is better. So which is best?

  7. #7
    No Hope For Me 1biggun's Avatar
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    I like the idea of the bullet guide being part of the mag well and not the trunion. this would make tuning thunds easier.

    I dont know what to think on the bolt getting damaged. is there a way to put a hardend collar around it or some thing to protect it?? I suspose you could just temper the end others here are better at the heat tread end of things.

    would love to see lots more pictures of it. Im working on a couple now (slowly) I like the mag being held in by just the mag latch and mag well fit.

  8. #8
    Gunco Rookie rk5n's Avatar
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    Sorry for the quality, All I have is a camera phone
    Last edited by rk5n; 11-05-2009 at 07:44 PM. Reason: uploader didn't work

  9. #9
    aka: SDK1968 dutigaf's Avatar
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    still think this is a nice build.

    dont feel bad about your pix.... ive got a good camera and still take lousy pix. :-)
    say what you mean & mean what you say


  10. #10
    Gunco Member petro116's Avatar
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    What kind of FCG are you using?
    I just switched out my Tapco hammer for a Romy one ,and had some good results.
    Check the profile of each hammer, and modify if necessary.
    Last edited by petro116; 11-07-2009 at 07:05 PM.

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