Hope you keep us posted on this, l am really curious about what would all of a sudden make a rifle not shoot a load it previously was. Without some altercation done to the rifle, bedding, changing the pressure point if it has one etc.
You must be a very experienced reloaded and marksman to shoot at a mile with no problem, and shooting a 6.5 creedmore to 1600 yards. When most say a creedmore is all but done at 1000, 1100 yards max.
I do have a couple questions, how many rounds have you fired after cleaning, and have you checked action screws for proper torque, scope ring screws also