Looks like you have a spot in your barrel that is building copper and it clears it's self once in a while and throws bullets out of the group when that little copper chunk comes loose. Just a guess but I have had the same thing happen before thought I was going to lose my fn mind trying to figure it out. Bore scope showed a small peice of riffling missing and a build up of copper in the gap a few more shots and the spot was gone and smeared up the bore.
