rear sight out of plumb

[chaneylake]

Did you make sure the front sight isn't moving in the dovetail.
Any side to side play in the mast of the tang sight when up in shooting position?
Make sure the screw that holds that mast to the base is tight.
Gary

front sight is plenty tight
zero side play in mast of tang
screws are tight

I have just having a difficult time in believing that such a light wind that I was shooting in on Sunday would give me that much drift

is the drift at 200 yards twice the drift at 100 yards?