When comparing everything involved apples to apples (ranges, velocities, temperature, altitude, wind speed etc) the below is how I know it to be. I am not that great at math so here it is in simplified form.
- Velocity of the bulllet when shot under identical conditions does not change whether shooting up/down hill or on a horizontal plane.
- The true verticle drop of the bullet is the same as well regardless if it is an up hill/down hill or horizontal plane shot. What changes is the effects of gravity on bullets that are shot up and or down hill. The degree on angle is a factor in this as well. Without getting into angles, cosines and so on basically just remember that when shooting up or down hill your bullet will strike higher due to the effects of gravity. Steeper angles and farther shots would adversely affect your shot if you shoot like how most sight in their rifles on a horizontal plane. Minute of a fox would be quite easily be missed under the right circumstances. Good luck this season and on angle shots hold low. How low is determined by the above factors.