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Discussion Starter · #1 ·
Just finished my first AR. I built the lower and purchased the complete upper. I first noticed that when I cycle the bolt, it would not close completely (just felt really tight). After a lot of cycling, it seemed to loosen up. I took it to the range today to put the first shots through it.

When loading a round, the bolt will still not close. The forward assist does not help. When I pull on the charging handle to eject the round, it feels like something is physically wedged, as it takes both hands and a large grunt to eject the round. If I manually feed one round (no mag) and close the bolt, it closes completely about 8-9 out of 10 times. I was shooting some 5.56 bulk ammo I purchased. When I tried my buddies .223 ammo, it actually cycled through some. It still hung up, but not as often. The upper is a full LMT upper w/BCG and charging handle. I also swapped BCG's with my buddy and my bolt worked fine in his Bushmaster, his showed the same symptoms in mine.

The ejected 5.56 rounds look like they are getting marked up by the barrel really good. Chrome lining a little thick? Something related to the BCG? Thanks for the help.
 
G

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Discussion Starter · #2 ·
Interesting. I can only suspect you didn't put the lower together properly.
Also, what kind of magazines are you using?
 
G

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Discussion Starter · #3 ·
Interesting. I can only suspect you didn't put the lower together properly.
Also, what kind of magazines are you using?
I am thinking more of the bolt/barrel myself. I swapped complete lowers with my buddy and mine ran flawlessly with his upper. It seems to be the bolt/barrel combo where I see the problem. I am using new magpul pmags.
 
G

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Discussion Starter · #5 ·
Is your barrel marked .223 specifically? if so the 5.56 probably wont function well, if at all in it.
 
G

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Discussion Starter · #6 ·
Is your barrel marked .223 specifically? if so the 5.56 probably wont function well, if at all in it.
lmt doesnt make 223 chambers.

swap your upper onto a different lower also, and see if anything changes.

if not, send the upper back to LMT.
 
G

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Discussion Starter · #8 ·
Is your barrel marked .223 specifically? if so the 5.56 probably wont function well, if at all in it.
.223 and 5.56 chambers are the same dimensions internally, it's the strength difference. 5.56 rounds create a lot more pressure than .223 rounds.
 
G

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Discussion Starter · #9 ·
.223 and 5.56 chambers are the same dimensions internally, it's the strength difference. 5.56 rounds create a lot more pressure than .223 rounds.
Actually, there are slight dimensional differences between the two.
 
G

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Discussion Starter · #12 ·
wrong wra wrong wrong wrong!

dimensional differences.

The AR15.com Ammo Oracle
Humm!! Guess I pulled up the wrong site -


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G

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Discussion Starter · #13 ·


But like i mentioned before, its a non-issue, as LMT does not make any bbls with 223 chambering.
 
G

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Discussion Starter · #14 ·
I would check your gas tube to make sure its not to long. The other question I have is did you have the head space checked? It is possible that it is not correct, even though you bought it as a complete upper.
Good luck.
 
G

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Discussion Starter · #17 ·
i bought a new gas tube and my gas key wouldnt fit around it.

does the bolt close with no ammo?

try takeing the upper off and pulling the bolt out and manually feed a round in the chamber and feel if their is any resistance from the bullet
 
G

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Discussion Starter · #19 ·
i bought a new gas tube and my gas key wouldnt fit around it.

does the bolt close with no ammo?

try takeing the upper off and pulling the bolt out and manually feed a round in the chamber and feel if their is any resistance from the bullet
The bolt does close without ammo, although it is does/did hang up a bit when letting it close slowly.

Update: Late last night I was messing with the bolt rings and took 1 off at a time. As each came off the problem became less and less noticeable. I took all three off and the problem went away. I cleaned them, re-lubed them and reinstalled. The problem is almost completely gone now. Do these rings wear in like piston rings? If so, is there any way to accelerate this wear to reduce the friction? Thanks for all the help everyone.
 
G

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Discussion Starter · #20 ·
Sounds let you were running it too dry. AR's like to run wet. The whole bolt should basically be wet(not dripping), gas rings and all, along with the rails that the bolt carrier rides on inside the upper receiver.
 
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