The upper was built with a DD 10.3 barrel, Troy lo pro gas block. Upper was a stripped Colt flat top we had laying around. We put a new extractor spring and o ring in there, running an H2 buffer and it runs fine.
Ok, quality parts used. So new extractor spring, o-ring, and an H2 buffer solved your issues? Nice. I still recommend you buy a new dedicated bolt group and not use the same for both uppers.
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