Ultra Mag uses a hat full of powder to give about another 400 fps at the muzzle over the .300 Win. With a 100 yard zero, this added velocity will flatten the trajectory at 300 yards by about 2-3 inches with 180 gr. bullets. Throat and bore wear will be greatly accelerated at a cost, which to my mind, is not worth the gain. If the job can't be done with a 180 gr. Mag, the shot is too far to take.
Trajectory is easy is figure.
Bullet drift from winds at all angles are impossible to calculate. Where you are standing you can gauge wind speed and direction using several electronic gadgets available from different companies. In my opinion, this is not fair or humane to the game being hunted. There's not one rifleman out of several hundred that has any business shooting at big game at distances beyond 250 yards. Obviously, many disagree.