GUN AR Crew: Bolt/barrel issues

Discussion in 'On Topic' started by ZCP M3, Aug 24, 2008.

  1. ZCP M3

    ZCP M3 Active Member

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    AR Crew: Bolt/barrel issues v. won't go into battery

    Got all the parts to make my new EBR and am having a pretty large problem. The BCG will not seat all the way into the upper and the cause seems to be the bolt not wanting to rotate in the barrel. The carrier slides freely, that little key rotates fine, but when I stick just the bolt into the upper/barrel, I cannot rotate it at all. The barrel is aligned properly in the upper and the nut torqued down to 65 ft-lbs, so as far as I can tell the barrel is properly mounted in the upper.

    This is a DPMS Lo-Pro upper with a brand new JP Rifles stainless barrel (.223 Wylde chamber) and a brand new LMT BCG.

    I plan to try a friend's Bushmaster BCG in it tomorrow, but does anyone have any ideas as to why this setup isnt working? :(
     
    Last edited: Aug 24, 2008
  2. yar1182

    yar1182 New Member

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    Not really sure if I understand. You should be able to rotate the bolt by hand. If it does so then make sure the bolt in the forward position in the carrier when you insert the BCG into the upper.
     
  3. Soybomb

    Soybomb New Member

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    The bolt goes back and forth in the carrier ok? You're trying it without the charging handle in?
     
  4. ZCP M3

    ZCP M3 Active Member

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    Yar,
    I can't freely rotate the bolt by hand if I insert it into the barrel no matter what I do. When the BCG is pushed in the bolt will try to start rotating and then sticks. Very hard to pull back out as well.

    Soy,
    I tried it without the charging handle and with, same issue. The charging handle slides fine, just the carrier slides fine, no go with a full BCG. The bolt moves freely in the carrier just fine and its got plenty of oil on it.
     
  5. yar1182

    yar1182 New Member

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    You know how if you insert the BCG with the bolt back it will not go into the upper. Because the cam pin is in the way. I'm thinking this is what he's stuck on. Bolt needs to be forward when inserting the bcg and charging handle into the upper. When inserted it will rotate the bolt.
     
  6. ZCP M3

    ZCP M3 Active Member

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    I made sure the bolt was pulled fully forward before inserting the BCG. It hangs up when the bolt goes into the breech and starts rotating to get into battery.
     
  7. yar1182

    yar1182 New Member

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    can you tell if it's rubbing on the cam pin or the bolt lugs? Is there anything suck in the bolt lug recesses?
     
  8. yar1182

    yar1182 New Member

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    Oh check the gas tube too. Is it hitting the key and keeping the BCG from going fully forward.
     
  9. Soybomb

    Soybomb New Member

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    Hmm I guess I'd take the bolt out of the carrier entirely, stand the upper upright on your leg, drop the bolt in and try to rotate it with your fingers and bottom through the bottom and ejection port. It will probably be a chore but at least you'll know the barrel extension is installed reasonably right and there should be room for the bolt to lock in.
     
  10. ZCP M3

    ZCP M3 Active Member

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    I'm 99% sure its binding on the bolt lugs. The carrier rides fine..the carrier and just the cam pin rides fine and if i shake it, the cam pin freely rotates over.
     
  11. ZCP M3

    ZCP M3 Active Member

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    The gas key and gas tube are properly aligned. No binding on either with just a charging handle, carrier, or CH/Carrier combo.
     
  12. ZCP M3

    ZCP M3 Active Member

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    This is where it fails. When I drop the bolt into the extension, it rotates about 1/8 of a key length then jams.
     
  13. Soybomb

    Soybomb New Member

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    That would lead me to think the barrel's extension or your bolt are off. Have calipers to check your bolt lug sizes with?
     
  14. yar1182

    yar1182 New Member

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    did you try lubing the heck out of the lugs.
     
  15. Soybomb

    Soybomb New Member

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    I was wondering about lube and a little use of the FA....but its been a while since i've assembled and upper and don't remember if it felt hard to lock at first.
     
  16. ZCP M3

    ZCP M3 Active Member

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    Not at my apartment. Tomorrow I'll be tossing in the BCG from a friend's Bushmaster to see if it works.

    They are way over lubed currently. The lugs, barrel extension, bolt, carrier, et. al.
     
  17. Painkiller

    Painkiller Sometimes remembering is better than forgetting

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    bent firing pin?
     
  18. ZCP M3

    ZCP M3 Active Member

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    firing pin is good, brand new bcg. I hope it's the bolt and not the barrel but lmt test fires their shit. :(
     
  19. A96HondaAccordCoupeEX

    A96HondaAccordCoupeEX Silver Member

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  20. ZCP M3

    ZCP M3 Active Member

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    Well here's the latest...

    My new LMT BCG works perfectly fine in my buddy's Bushmaster, which has over 2000rds through it. His Bushmaster BCG with the same amount of rounds works perfectly fine in my new JP Rifles barrel. :confused:

    Are the LMT/JP components just so close to the respective tolerances that it's just not a good combo? Or is the barrel just out of spec?
     
  21. Soybomb

    Soybomb New Member

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    Well I'm not a gun smith and I wouldn't say to take my advice but I would think thats pretty close, put in my bcg and give it a love tap with a rubber mallet :big grin:

    (which may be a really terrible idea, I'm known for having those from time to time)
     
  22. ZCP M3

    ZCP M3 Active Member

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    It's far from close, it will turn about 1/8 as far as it should. I FORCED it in once and it was a bitch to get back out. Time to send back the barrel. :(
     
  23. A96HondaAccordCoupeEX

    A96HondaAccordCoupeEX Silver Member

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    Is this a completed rifle? Pull back CH and release. It wont lock in place?
     
  24. ZCP M3

    ZCP M3 Active Member

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    Completed rifle. Can't get it to go in far enough to even close the upper to the lower. I let gravity drop it in and that did not work either. A strong smack with a rubber mallet popped it in and it was almost impossible to pull out.
     
  25. yar1182

    yar1182 New Member

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    I've heard that the bolt over times wears itself to the barrel and they become a matched set. I've always sold the barrel and bolt as a set when I moved on to a new barrel for the AR. I never heard of a problem like yours.

    I'm not sure what my AR smith would do. He might file the edges of the bolt lugs until they mated properly with the barrel. I'll give him a call when he gets home tonight.

    The bushmaster bolt and barrel are probably worn in thus they worked. Your lmt and JP are both virgin.
     

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