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Thread: Upper assembly problem

  1. #1
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    Upper assembly problem

    I picked up a colt 16 inch barrel from copes distribution at the creek for $100 bucks I found upper receivers for $40 and everything else I needed for a additional 50.As ive torqued the barrel on i notice the bolt will hang up on the locking lugs. If i press upward on the bottom of the carrier it will click into place but it hangs trying to retract. Did i get some out of spec crap? Prices that seem to good to be true.. i should know better at 52 years old...
    Its a dog eat dog world out there,and I'm wearing milkbone underwear..

  2. #2
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    Whose upper receiver?

  3. #3
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    I looked at Copes website - was it an Anderson upper and an ESS barrel? The two things that immediately jump to mind are 1) the barrel extension pin was not placed properly or 2) the locating slot on the upper receiver is just a skoosh off centered. I'd think bolt or bolt carrier problems would be third, but less likely.

    I'd try another bolt carrier group, if that worked, then I'd swap bolts between the carriers and see if the one that worked still worked, that would rule out the bolt or bolt carrier.

    Good luck.

  4. #4
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    Upper was in a box of hundreds marked $40 bucks each proably factory seconds

  5. #5
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    I'm not recommending this because I'm not sure where the hang up is at. Just throwing this out there... So let's pretend the barrel is rotated slightly off center in the upper causing the bolt not to engage the lugs properly. It's possible, not saying it's the correct thing to do, but it's possible you could lightly file one edge of the slot in the upper receiver, the edge that you believe the barrel should rotate towards. Hold the barrel in place or shim it as necessary and lightly tighten down on your barrel nut and check for alignment. If it engages or gets better then you're on the right track. If this a route that's considered, go slow and disassemble, file, and reassemble multiple times and as much as needed until the bolt fits perfectly. I can't stress going slow enough! Shim the pin in the slot and torque. Again this is not saying you should do this, but just an idea of a possible fix. Is it right, probably not, would it work, possibly so. That part is up to you though. But I'm with the others, test with other bolts/bolt carriers, and if you can, a good barrel you know that fits. Rule out ALL possibilities before attempting something like that. Cause once it's filed, that's it.

  6. #6
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    One more word of caution with filing though. If the barrel has a front sight, its possible, that once everything is in place and the bolt lugs engage correctly, that the rear sight windage would have to be adjusted really far one way or the other. It's possible but then again it could line up just fine...

  7. #7
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    Did you install the gas tube already?

    If the gas block is too far to the rear, the tube can bind the carrier key, and consequently the bolt lock-up with the extension.

  8. #8
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    If the cuts in the extension are lining up with the ones in the receiver, then you can rule out a poorly timed barrel due to an out of spec barrel pin alignment notch or bad placement of the pin in the extension. Check the diameter of the carrier bore in the upper to make sure it is 1", and that the barrel socket is machined centered. There should be a slight step in the area of the bore where the lip of the extension rests. It is possible that the socket itself was machined too high, or that the bore itself too large. If all of this checks out, try a different BCG to determine if the one you are using is out of spec.

  9. #9
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    Sounds like some Dykem #107 is gonna come in handy!

  10. #10
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    Quote Originally Posted by HelloLarry View Post
    Sounds like some Dykem #107 is gonna come in handy!
    Or a black sharpie.

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