
Originally Posted by
O3SKILL
Factory new Rifle, cleaned, well lubed, gas key tight/staked, gas block tight/straight/pinned, barrel, barrel nut and rail all appears to be properly installed and tight. Took it to the range for a BZO, fired around 35-40rds, accuracy compared to my norm was disappointing, overall extraction was pretty weak with intermittent FTE's, stovepipes, one double feed. Ammo was 2011 Winchester RANGER M855 (all of my other 556 AR's love it), mags used were known good magazines both USGI and PMAGS. I've never experienced any problems with a AR-15 like this before. Always used high quality weapons, parts etc and good quality ammo and mags. Looking at the brass it seems that there is something in the chamber that is denting/gouging into the brass and causing the extraction problems. The flash is drowning, but there are also scratches down the length of the brass on the same side as the dents and some gouging on the case rim from the extractor having to work hard.
What do you malfunction guru's think is going on. Chamber out of spec?

Normal marks but extreme dents.
The lengthways scratches comes from the round being drug over the barrel extension lugs. The dent as big as it is comes from an over-gassed rifle slamming them into the rear of the ejection port.
If those dents have a sharp line they are hitting the rear of the port. If rounded they come from the shell deflector. I think the gas port in the barrel is too large. Try an adjustable gas block to cut back on some of the gas.
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