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Thread: problem headspacing ak74

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    Gunco Member balls2elwall's Avatar
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    Default problem headspacing ak74

    hey so im almost done with my bulgy ak-74 its a virgin barrel so ive riveted and assembled the reciever and pressed the barrel in. while checking the headspacing the bolt closes on both the no go gauge and a live round. The bolt is stripped and closes super easily on both. so i tried pushing the barrel in a little bit further but then the bolt wont even close on an empty chamber the notch on the right side of the front trunion blocks it. so i pushed it back out a little (not fun) and it still closes really easily on both with a lot of slop. No matter how many youtube videos and my agi building the ak from a parts kit video i cant figure out whats wrong. so just to clarify the no go gauge is put into the chamber, the stipped bolt is inserted onto the rail, pushed against the no go gauge, rotated to the right till the top knob hits the receiver? if it rotates easily to the receiver then the barrel is not in the right position?

    thanks in advance

  2. #2
    No Hope For Me Coils's Avatar
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    Off the top of my head, how tight is the barrel fit in the trunnion?
    A really tight barrel will "jump" as it's being moved, these are hard to head space because you can't get them to move just a few thousandths.

    It sounds like you are right there and only off a tiny bit.

    Can't comment on the "right side notch" thing, I'd need to see it to even try.
    "Government is not the solution to our problem, government is the problem" Ronald Reagan

  3. #3
    Gunco Member balls2elwall's Avatar
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    hmmm when i get home from work tonight ill take a picture and post it. i think i may need to push it out just a tiny bit. I was trying to put the dust cover on and its super super tight. thanks coils.

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    No Hope For Me Coils's Avatar
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    Yeah it sounds like it's just moving a little more then you need it to, first it was too much gap then it wasn't enough, that's why I thought about the barrel "jump" from it being tight.
    Your welcome.
    And I'll try to check back if you put up a pic.
    "Government is not the solution to our problem, government is the problem" Ronald Reagan

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    Gunco Member ammoboy2's Avatar
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    The barrel stickyness while pressing to get the just right headspace can be a real bitch. I recommend the following process to aid in getting the headspace correct:

    1) press barrel in close to correct
    2) measure gap between rear sight base and front trunnion with feeler gauges
    3) take feeler gap measurement and remove estimated headspace overage plus about 0.005 inches.
    4) press barrel in further with measurement of step 3 above held between RSB and FT.
    5) check headspace again and go to step 2 and repeat as needed.

    This at least limits the barrel jump and reduces the frustration a little bit, but can not prevent it.

    Also I place the guage in the bolt prior to rotation to make sure it is within the bolt head properly.

    If you start with a matching kit and measure the fsb to ft gap prior to demil pressing of the barrel it makes the build really easy and fast, because to have an excellent estimate of where the barrel needs to be for correct headspace.

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    Gunco Member ammoboy2's Avatar
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    Forgot to mention the feeler gauge will get a bit stuck during the press of barrel but you should be able to remove it after taking the pressure of the barrel assembly. Also do not use your favorite feeler gauge, they take a permenant set or damage if you get to aggressive, same for the RSB edge. I have done this on several with great results, sure takes the pain out, especially for the new barrel installs.

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    Gunco Member STGUSN's Avatar
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    I have found that using white lithium grease or anti seize in the trunnion before installing helps eliminate barrel jumping. I ran into a similar problem with my PSL build. I was using the all thread method for that build. What method are you using to install the barrel?

  8. #8
    White Cracker 4thIDvet's Avatar
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    Default Balls2elwall...

    Quote Originally Posted by balls2elwall View Post
    hmmm when i get home from work tonight ill take a picture and post it. i think i may need to push it out just a tiny bit. I was trying to put the dust cover on and its super super tight. thanks coils.
    Do not go by the dust cover... Listen too what the guys are saying.
    Your dust cover, even matching numbers, could have been banged around at some time.
    The thin metal strip, back of the dust cover, under the recoil spring hole.
    Put cloth on it, now take pliers and gently bend it out till it fits in place..Just a tiny bit, adjust accordingly..
    Barrel jump.. Yup, fun...In out, in out...
    I had a Romy did that.. Think that is the one I set the 120' 7" record AK toss with.
    We use a press for the barrel.. Took it out, just a very slight Brillo polish and lube like STGUSN is saying.
    Not sure if it was the lube or the toss. But it worked.
    But listen too the guys, they are light years ahead of me on building.
    Re-check when you put your barrel pin in...
    "Man needs but two things to survive alone in the woods. A blow up female doll and his trusty old AK-47" - Thomas Jefferson 1781


  9. #9
    No Hope For Me 1biggun's Avatar
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    the bolt wont even close on an empty chamber the notch on the right side of the front trunion blocks it.
    OK lets stop an think here. the bolt closes when the barrel is in but not back enough for correct head space. your stasting when you move the barrel back the bolt now will not rotate in because it hits the trunion?????? that does not make sence. the trunon to bolt clearance does not change regardless of were the barrel is.

    if you can not get the bolt to close on a empty chamber then the barrel is to far back or there is a issue witht he barrel either being chambered to deep or a possable issue with he extracer grovve is to shallow or more than likey indexed wrong.

    taKe felt pin an mark the areas were contact might occure an see whats hitting.

    its also likely you just pushed the barrel to far back an the bolt is hitting the barrel.

  10. #10
    No Hope For Me 1biggun's Avatar
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    BTW I PRESS THE BARRELINTO THE TRUNION AND SET HEAD SPACE AN DRILL THE PIN HOLE BEFORE EVER INSTALLING THE TRUNION IN THE RECIVER. EASY ON A SCREW BUILD AN IF ITS A RIVET BUILD i JUST PRESS THE BARREL OUT AN RIVET AND THEN REPRESS TO WERE THE PIN GOES BACK IN DOUBLE CHECK AN DONE.

    I USE JUST THE BOLT NO CARRIER WHEN DOING HEAD SPACE. IMO IT GIVES A MORE PERCISE MEASUREMENT AS THE CARRIER CAN COCK THE THE BOLT AN GIVE YOU A FALSE READING. ITS ALSO A LOT EAISER IMO MOVE THE BARREL IN AN OUT WITH OUT A RECIVER IN THE WAY. USE NEVER SEIZE AN CHAMPHER THE HOLE ION THE TRUNION .

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