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Posted: 5/14/2014 5:58:22 PM EDT
| OK, first off, first time posting... read quite a bit on here and its a great site so Im glad I found it... Have learned quite a bit already, but didnt really see my exact issue, maybe someone can help. Kinda new to the AR world, so sorry in advance if my post doesnt make sense..... I have a buddy who built 2 AR's... one fires fine, one doesnt... the gun does not auto cycle.... it will push the bolt back far enough, eject the round sometimes, but never go far enough to grab another round... sometimes the spent round would get stuck... so he took his gas block off and made sure everything was clean and lined up, but it back together and still the same result. He borrowed my bolt to try and still the same outcome. We swapped buffer springs and still nothing... We put his lower assembly and a different upper together and it worked fine... We then put his upper assembly on a different lower and still the same issue... He bought another barrel and swapped everything over and now it works great... so he narrowed it down to the barrel, possibly... what would cause something like this? I was going to buy the barrel from his for a really cheap price, but I want to make sure I can use it in my next build... thanks in advance |
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The barrel?? Where did you come up with a problem with the barrel other than the gas hole being out of spec.
Sure sounds like a gas problem....meaning you are loosing gas from somewhere. Gas block...gas tube...Gas key on bcg...rifle is short stroking for some reason. Since lower works with other uppers...not a buffer problem. ETA: Re-read your post. Since another barrel seems to work than problem might be that the gas block is leaking around the hole in the barrel. I am sure other far more experienced members here can give you a much better explanation. |
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Barrel should be easy enough to fix.
Its either the chamber that is too tight and a quick re-ream with a reamer and matching bolt should solve that problem, Of if the gas port is too small, then it can be reamed out to the needed size. 11.5" barrel, .625: dia., 3.850" from muzzle; Port sizes from .081" to .089" 11.5" barrel, .750" dia., 3.850" from muzzle Port sizes from .086" to .094" 14" barrel, .625" dia., 8.375" from muzzle; Port sizes from .063" to .078" 14" barrel, .750 dia., 8.375" from muzzle; Port sizes from .070" to .086" 16" barrel, .625" dia., 8.375" from muzzle; Port sizes from .063" to 078" 16" barrel, .750" dia., 8.375" from muzzle; Port sizes from .070" to .086" 20" barrel, .625" dia., 8.375" from muzzle; Port sizes from .086" to .093" 20" barrel, .750" dia., 6.875" from muzzle; Port sizes from .093" to .096" 24" barrel, .825" dia., Port size .089" 20" 6.25" .093" 16" 8.50" .063" 14.5" 6.75" .067" 11.5" 3.875" .076" 10.5" ? .089" |
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