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AR15 help

My 7.62x39 ar pistol had similar issues minus the dry-firing part. Found a youtube video of a guy slowly turning an oiled 12 gauge brush in the chamber to simulate a break in period and that worked for me. I guess there were some rough spots on the lugs. No problems in about 1000 rounds since then.
 
check your gas tube for clearance, it may be rubbing
This

I put a 5.56 upper together awhile back. It would go into battery just fine, but the bolt would stick closed, and I mean it was TIGHT. I would have to mortar it to get it back open. I thought it was either the chamber or the BCG, but it turned out to be the gas tube.

I never thought a gas tube could make the BCG stick that tight, but it did!
 
I'd vote for the gas tube. Had the same issue before. Dry firing it just helps seat the BCG on the misaligned tube from the hammer strike. Remove the block and tube and see if it still does it.
 
Either, the gas tube is binding or you've got an out of spec bolt. ALWAYS check the gas tube / carrier interface after the tube is installed. Before taking the whole gun apart, do this:

Remove complete bolt carrier group
Disassemble BCG
Insert stripped carrier into the upper receiver
Slide it back and forth to see if there is any binding or resistance when it contacts the gas tube.

If it is sliding freely, then you have narrowed the issue down to the bolt and barrel extension fit.

Continue troubleshooting by reassembling the BCG with a different, known good bolt.
Insert known good bolt into the gun.
Move back and forth to see if there is unusual resistance when it locks and unlocks within the barrel extension.
If the known good bolt works, then the original bolt is out of spec.
If it doesn't work, the barrel extension is out of spec.
 
Thanks for all the help guys let me try the easy stuff first. Now reading this realizing I may know less than I thought. I have assembled several but not sure how to check gas tube and few other suggestions. Will try other bcg in good gun and see how that goes.
 
Thanks for all the help guys let me try the easy stuff first. Now reading this realizing I may know less than I thought. I have assembled several but not sure how to check gas tube and few other suggestions. Will try other bcg in good gun and see how that goes.
See post 16.
 
Thanks for all the help guys let me try the easy stuff first. Now reading this realizing I may know less than I thought. I have assembled several but not sure how to check gas tube and few other suggestions. Will try other bcg in good gun and see how that goes.
Good luck let us know when you get it squared away!
 
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