If I had to guess it would be the barrel is under torqued a bit and the front sight base assembly is not centered over the bore center line. Look to see if there is contact between the top of the extractor on the bolt and the top edge of the cut out on the back of the barrel. If so or very, very close this would indicated the barrel is not indexed all the way. This is my guess but I will defer to Mr. Laidlericon.