For a deer, antelope or coyote gun I zero for a maximum bullet rise above the line of sight of 2.5 to 3.0 inches. With my 6mm-06 or 7mm STW they are "dead on" at 300 yards and only about 7 inches low at 400 yards. As far as the bullet being not exactly "dead on" at distances other than 300 yards, no problem. I know the trajectories of all my rifles. I knew the trajectory of my 7mm Weatherby I bought when I was 15 years old, which was 43 years ago. Every time I shoot I think about trajectory and wind drift. For rimfire rifles or for my .17 Hornet which I use for much smaller animals, I zero for a maximum rise above the line of sight of 1.0 inch. Again, I think about trajectory and wind every time I shoot. For example, during the past week I shot two squirrels off my bird feeder with my 124 FWB pellet rifle. It is zeroed "dead on" at about 30 yards so is about 3/8th-inch low at 10 yards, the distance to my bird feeder. I did not center the cross hairs on the squirrels' heads. I aimed the cross hairs almost at the top of their heads. I think if one tries to account for trajectory every time he shoots, eventually it will become second nature, even under extreme excitement like when one sees the biggest buck in the county.