Bad upper receiver? Need opinions

LARUEminati

New member
Has anyone out there ever gotten a bad upper receiver that didn't jive with the bolt?

I've been diagnosing what I thought was an under gassed issue (bolt would never come back far enough to even stovepipe or come close to ejecting brass) and it's taken me awhile to diagnose what's going on.

What I've come across is if you put any pressure upwards or downwards on the rear of the bolt while it's in the receiver the bolt is binding up in the upper and you can't move it at all. The upper portion of the bolt next to the carrier key is rubbing badly. When I slide another "nicer" bolt into the receiver it gets stuck about half way down and you need to force it to get it past that point and into battery. I am envisioning that when you fire the carrier is tilting and binding up and it's only coming about half way back, not even far enough for the neck to come out of the chamber. This is a 10.5" barrel and the M855's were doing 2660 over a chronograph. No other signs of gas leaks, gas port mic'd between .073-.076

I'm thinking the receiver is bad, this is a new upper and it's never cycled a round even with M855 green tips. I even went as far as changing to shorter springs and removing all of the buffer weights. I am going to send it back to the manufacturer but I've never seen this before.
 
Not the same problems but I've gotten an out of spec stripped lower before. No reason it couldn't happen to an upper.
Was your upper a stripped or complete upper?
 
Kudos for troubleshooting it that far, it sure doesn't sound right. I just checked one of mine, well worn though it is, it's perfectly smooth with upward pressure.

I'd look for any obvious problems that could be easily sanded/filed smooth, then send it back I guess.
 
Originally Posted By: crapshootNot the same problems but I've gotten an out of spec stripped lower before. No reason it couldn't happen to an upper.
Was your upper a stripped or complete upper?


It's a complete upper from CBC Industries. I think either the upper is out of spec, tweaked of just the tolerances or the upper don't match up with the tolerances of the supplied bolt.
 
Originally Posted By: 204 ARKudos for troubleshooting it that far, it sure doesn't sound right. I just checked one of mine, well worn though it is, it's perfectly smooth with upward pressure.

I'd look for any obvious problems that could be easily sanded/filed smooth, then send it back I guess.

Thanks. The upper feels tweaked because on other uppers if I twist the bolt left and right in the upper it has a little wiggle both ways. On this upper it'l twist to the left slightly but not at all to the right. Any pressure on the rear of the BCG in any direction binds it right up. First time I've seen this.
 
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