I assume that when you say it shoots "really well" you mean at shorter ranges; to know how much shorter would be useful. Also, what is "really well"? If it is true that groups at say 100 yards or 200 yards are very good, you can probably eliminate a scope problem or technique as a cause. The most likely cause would be velocity variation.what is the typical root cause and what are the standard steps to remedy this problem?
have a custom rifle that shoots really well and after shooting a group at 550 yards, my vertical string was pretty horrible, close to 8"
I think to barrel could be considered broken in at this point. Earlier in the thread you mentioned changing brass. If you shot one brand of brass at short range and another at long range without a new load workup for the brass used at longe range, this could be a big issue.is it possible that my barrel is still breaking in? there is only 110 rounds down the tube