I'll be going on a sheep hunt next year.I was planning on getting a custom turret put on my scope matched to my ballistics. The problem with at I was told is hunting at different elevations. will change my point of impact. One turret setup at !000 feet will shoot over a sheep at 7000 ft and vise versa. Is this true? Is the differance that much? What are my options? I'd really like to have a turret to dial in instead of holding over. Any help?