I am not into AR's but could not resist any longer and got a DA556.
I lubed up the new rifle and put about 75 rds through
and got a couple failure to extract.
Disassembled the bolt and cleaned but it continued to get worse.
A search turned up the extractor o-ring and spring core fix.
With an o-ring in I got 200 rds through and got one more FTE.
Is this a macgyver fix or should there be a o-ring on the extractor spring.