My thoughts are that the problem is the 20 MOA rail.jlow said:Kings X - thanks! That sounds like a great idea! Much appreciated!
One thing I would ask you to elaborate more on is this idea of a weak spring and larger group at the 1k setting. I presume this relates to the ability of the return spring pushing up on the erector tube with the tube going higher and the spring longer for the longer distance shot?
So to bring that further, one can visualize more potential problem for the longer distance setting?