If he is so concerned about the cost of ammunition,he bought the wrong cartridge.The only way to know where the bullet will impact at a given distance is to shoot the load in your rifle.However the calculation below will provide ballpark estimates.Realize that in order for the calculation to be at all close,you will need to know the exact velocity that the load produces in the specific gun.Using velocities posted by a manufacturer in place of the actual velocity can result in very large errors as distances increase.As well you need to select the exact bullet used or the exact ballistic co-efficient for the bullet that you are using.Be aware that manufacturers published B.C. are often not accurate for your conditions.
If you had posted out to 400 yards or so,small errors would not be so significant,but at 800 yards or 1000 yards,a small error can result in a big difference in the point of impact.


http://www.eskimo.com/~jbm/calculations/traj_basic/traj_basic.html