...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?
I calculated the bullet drop in inches for you at two different altitudes and temperatures, for 500 and 800 yd range. This is bullet drop from the muzzle, not from a 100 yd zero.
Altitude (ft) 1000 ft. 7000 ft
Range (yds) 500 800 500 800
59 F -61.0 -180.4 -58.3 -166.8
0 F -62.4 -188.2 -59.4 -172.2
The short answer is that you should be fine zeroing and determining ballistics for the turret at a low altitude and hunting at a high altitude at up to 500 yds. The advice you got regarding missed shots applies to longer ranges.
The altitude change alone causes about 3" difference in bullet drop at 500 yds. You could hold 3" low at high altitude and be fine. If you zero and determine ballistics at low altitude on a hot day, and then hunt at high altitude on a cold day, the difference in drop will be smaller, say about 1-1.5".
However, I recommend that you make the altitude adjustment in your ballistics before ordering the turret, and calculate the drop adjustment for a middle altitude, say about 4,000 ft. Then the difference between your turret drop and the actual drop will be on the order of 1" or less. Your group size at 500 yds will probably be larger than 1".
I also recommend using printed turret labels from Custom Turret Systems. I've tried them and they work very well. For example, you could get a set of four labels for range work at 1,000 ft and another for hunting at say 6,000 ft. Total cost would be $50.