Do you have POI shifts with a rifle not sighted in while attached to the Reaper? That would seem to add substantial weight directly to the rifle and would affect muzzle rise and recoil speed and affect POI during long-range shots?
I don't have any issues at all out to 865 yards hitting 1 moa steel. For hunting I'm not trying to shoot X's on paper. All five animals I harvested this season were shot with that setup. My hunting rifle is a 7mm RM Proof that does .25 moa all day long... at least when I'm doing my part!
~Robert