Looking at the round in your picture it seems as though you may have a chamber issue as mentioned earlier, It does appear to be contacting the lands, the round looks to be a standard seating depth which should not touch the lands. If the chamber is not cut properly or is rough, that can cause all kinds of issues on extraction. Trying two different bolts and the same issue indicates that the bolt is not necessarily the problem. I would send it to a well known and respected gunsmith who could diagnose and correct the problem. Another question is, how does it shoot?