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Thread: .308 AR build issue - am I screwed?

  1. #1
    Team GunsNet Silver 07/2012 NewbieAKguy's Avatar

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    .308 AR build issue - am I screwed?

    So I finally got my franken-gun .308AR build completed a couple months ago. I took it to the range last month to function check and start breaking in the barrel. About halfway through the barrel break-in (about 20-25 rounds or so) I started getting tapped on the nose by the charging handle (ZEV Technologies ambi). I take a closer look at upper receiver where the latch hooks onto and see this: https://forum.308ar.com/uploads/mont...89dafabb2c.jpg

    After posting on another forum and looking into this particular charging handle and trying to find out any other possible reasons the charging handle is moving back during firing, it turns out ZEV's design leaves much to be desired. I dumped the ZEV for a BCM I was able to find (didn't know BCM stopped making .308 AR charging handles) and tried it again. Charging handle still comes back during firing. I can pull on the right side of the BCM (as if shouldering the rifle) and it won't release unless I actually pull the swiveling latch on left side.

    This is where I can use some input/advise from any gunsmiths or experienced .308 AR builders:

    1. What is causing the charging handles to come back in the first place?

    Is it strictly recoil or something else? I didn't see any signs of abnormal or excessive wear when moving the bcg by hand (the two halves separated and holding upper upside down). When firing the rifle I don't feel anything out of the ordinary; no overgassing or whatev, feels like normal .308.

    Possible I need a different (heavier?) buffer, buffer spring, or both to prevent over-travel, if that's even the cause?

    2. With the charging handle area of upper receiver as worn as it is now, is it still usable if I fix the cause, or it is ruined and the charging handle will move back no matter what now?

    If allowed I can attach the link to the discussion I posted on another site so everyone can see the parts used and input already given.

    Thanks.
    "The God who gave us life, gave us liberty at the same time; the hand of force may destroy, but cannot disjoin them. ... Can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are the gift of God? That they are not to be violated but with His wrath? Indeed I tremble for my country when I reflect that God is just: that his justice cannot sleep for ever."--Thomas Jefferson

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    Forum Administrator Schuetzenman's Avatar

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    Sorry no experience with AR designs other than 5.56 types. That said they should work the same as the smaller caliber versions. If the handle is moving back it has to be getting dragged back by the bolt carrier gasy key that it fits inside of. I would check the width and diameter of the key where it fits inside the charging handle. Then i would check the inside of the charging handle and the opening the key passes through. A clearance must be tight. Or last thought the bolt carrier is tipping under recoil and binding inside the charging handle. The heavier buffer might help with the situation if tipping is the root cause.

  3. #3
    Team GunsNet Silver 07/2012 NewbieAKguy's Avatar

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    Quote Originally Posted by Schuetzenman View Post
    Sorry no experience with AR designs other than 5.56 types. That said they should work the same as the smaller caliber versions. If the handle is moving back it has to be getting dragged back by the bolt carrier gasy key that it fits inside of. I would check the width and diameter of the key where it fits inside the charging handle. Then i would check the inside of the charging handle and the opening the key passes through. A clearance must be tight. Or last thought the bolt carrier is tipping under recoil and binding inside the charging handle. The heavier buffer might help with the situation if tipping is the root cause.
    My only other experience with .308 ARs is the POF I used to have, and I didn't have any issues with it....but it wasn't a franken-gun either. I've had the upper off and run the bolt by hand (while upper is upside down) and nothing seemed to be dragging. I guess I can try moving it by hand right-side up and see if any difference. I guess I'll break out the micrometer and see if I can measure some dimensions.

    You mentioned a possibility of the handle being dragged back. Could it be possible that the BCG is traveling back farther than it should and therefore pushing it out? I only ask because I don't recall seeing any drag marks on the BCG/gas key or underside of handle, but doesn't hurt to look again.

    Thanks for the input S-man.
    "The God who gave us life, gave us liberty at the same time; the hand of force may destroy, but cannot disjoin them. ... Can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are the gift of God? That they are not to be violated but with His wrath? Indeed I tremble for my country when I reflect that God is just: that his justice cannot sleep for ever."--Thomas Jefferson

  4. #4
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    I've got a Colt Commando 11.5" upper that I put a Osprey Defense piston kit on ... after a while it started tapping me on the nose ... replaced the charge handle, no change ... replaced the upper (the catch for the handle latch looked worn) no change ... took out the piston kit, no more nose tapping ... put the original upper back on, fine ... I think it was unlocking too harsh with the short barrel, I installed the kit on a 16" upper and I don't have the nose tapping problem.

    I didn't see if it was a direct impingement or piston but I didn't see any contact with my piston/bolt carrier

    I had an H2 buffer in it so I didn't try any others

    I drilled a small hole in the upper where the handle latches and used a pin-file to make it square, works fine with the new handle ... I pitched the old handle but it probably would have been fine

    ==

    Maybe try an adjustable gas block?
    Last edited by kimberkid; 05-25-2019 at 10:11 AM.

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