I purchased an upper last week at a gun show from a local who builds uppers. I put about 75 rounds through it both factory and hand loads without any issues. I have Rock River Lar 15 and I use it's lower with the new upper. Today I was attempting to finish zeroing the scope with a handload that I will use for long range shooting when I noticed that the bolt did not stay open when the last round was fired, I tried some factory loads and they also failed to cure the problem. Any way I wanted to finish sighting the scope and I went back to my handloads and fired a round, the gun would not fire the second round, I then discovered that the empty round did not eject, I finished my scope sighting in by manually ejecting the rounds.

I went home and checked my owners manual trouble shooting section, possible reasons for bolt not staying open are bad ammo, tried three different loads, two factory and my handload, bad magazine, magazines look fine, corroded bolt latch, it looked fine, I gave it a good cleaning. I checked out all the possible causes for failure to extract, took apart the bolt carrier and cleaned it, also cleaned the chamber using a 357 brush and patches, there was some carbon but not a lot. Went out and tried it again, cases will still not eject, It then tried my other upper and it fired without a hitch, I then took the bolt carrier from my other upper and tried it, same problem, cases won't extract. I know for sure that the problem is not associated with the lower reciever or the bolt. Any suggestions before I have to bring it back to the seller, it's a 50 mile drive one way to his place of business.

Extractor? Had an OLY Arms upper that wouldn't extract. Took it to local well know gunsmith 4 times, who said there was nothing wrong. Fifth time big guy wasn't there, one of his helpers put a stronger extractor spring in. Worked after that.

"Local guy that builds upers" probably didn't align the gas block which could be causing the short stroking issue. Also, double check your loads and make sure they were up to speed. AR's need gas to cycle and weak ammo can cause similar issues.

Details about the new upper would help.

double post

Take it back to him and have him align the gas block with the gas port.

Probly didn't tighten the gas block screws very well and the gas block moved during your first 75 rounds. Just needs to be realigned and tightened

I talked to the builder earlier today, he suspects the gas block, will fix it, test fire it.

Sounds like its not extracting, but ejecting fine.

If thats the case, gas block is first place I'd look too.

I took it to the guy who built it and he took it apart while I was there, sure enough the gas tube had moved, lots of black soot around the tube. He is going to repair it and test fire it before he returns it back to me.

same thing happened with my 458 socom. 20 rounds and the GB moved ahead. no gas no eject.

I put about 75 rounds before it started to mess up, it was just starting to shoot good groups, .800 inch group at 100 yards, 2 1/2 inch group at 200 yards, and I was just getting started.

My rifle had the exact same issue. The local lizard that built it did not properly "dimple" the bbl to lock down the gas block. After about 500 rounds it would not eject. The gas block moved forward about 1/8" effectively shutting of the gas needed to cycle the bolt.

As I learned more I discovered lots of other issues as well. Which were easily corrected. My rifle was the sum of a lot of really good parts just slapped together.

There are a lot of people building AR's that don't know what they don't know.

Lefty C

Dimple? Interesting.

I've put so many blocks on with set screws and Loctite 640 and no dimple at all that have never moved, that I think its more the assembly person not having a clue rather than missing dimple.

They are so easy to put together, that folks that shouldn't, do.

Worse yet some call themselves smiths....

thanks for the info on the Loctite rost. was wondering what flavor to get. only dimpleing I know about is on the bcg.

640 bearing retainer, when ready to remove you'll hvae to heat it up with a propane torch and beat it off with a 2x4 and 2 pound or 3 pound sledge....

yeah buddy!! that sounds like fun.

I don't know the number but red lock tite seems to be in vogue.

Blue loctite and rockset is all I ever use. I do dimple barrels with set screw gas blocks though. Very easy to do.

640 green bearing retainer has a long list of good things even with AMU Ft Benning... rifles being dropped 6 feet to concrete and landing on the front sight base which is only set screwed( for windage adjustment upon initial zeroing) and loctited, having the zero change .25 moa... seems the Marines had the same results a few times...

Use what you want, but be aware 640 is badazz and worse to get back off.