I might have misread, but did you run dirty brass thru the rifle? Or was that the smith in testing?Well 6 months on and 487 rounds more thru the gun using same developed loads supplied with the gun and not one single failure to extract / difficult or hard extraction.
I guess all it needed was the bolt replaced by someone who knew what they were doing in the first place!!
Still waiting on an apology from Mr Supplier but I guess I will never see it