Is the rifle bedded? Also, have you picked up some factory ammo to see if that has any difference in groups, just to rule out anything that you may not be seeing during reloading? I have 6mm Creed PBB barrel I have built on a Kelbly Atlas Tac and it is accurate, but I have only test fired it with factory ammo, no reloads. I have got .50 and .75 3 shot groups at 100yds with Hornady 103gr ELDX and Hornady 105gr black ammo. I was going to purchase some Match grade ammo after I finish Cerakote to see how they shoot before I put it on the market. Just something you may want to try before investing more in reloading supplies. My barrel is 7.5 twist.