This is happening when shot through a [b]dirty[/] barrel, probably had 20 round though the barrel before I shot these groups. I had shot the rifle a week earlier and hadn' t cleaned it. I loaded some new rounds to try to find the OAL it liked with 5 sets of 5 rounds, all at different OAL' s. I only shot 2 groups (ran out of light) but both groups did this exact same thing. First shot was a stone-cold barrel. Next 4 shots were about 30 seconds apart after the first shot. I was shooting over sand bags at 100 yards in calm, dry conditions.