I'm not sure other than that's what he told me they found with it. That said, he tried shooting it right out of the box with it jamming every shot, and just manually pushing the bolt closed, and it still was very inaccurate, so I don't think them cleaning up the chamber was the cause of the accuracy issue.

That said, I just assumed they knew that it was a burr since that's what they said, and after they worked on it, it no longer jammed, however I didn't personally see the burr so I can't be 100% sure that's what it was.