Another choice, and I know it's not what you asked....
take the scope off for now and shoot the rifle with the iron sights.... get as good as you can with them... then put the scope back on and see how you do.
I bet you will be surprised.
I do have to agree the the drop the scope down to the barrel.. I have several see through scopes on smaller caliber rifles (22lr and 9mm) and they don't seem to adjust well. I suspect on that hoss of yours it makes things worse.