Can you explain mtnman why that would be true? I am curious how bullit path would arc down then up.Is it Site height to muzzle?
Maybe these illustrations and quote from another website will help:
Begin quote: We have a tendency to get the "line of sight' mixed up with the "line of bore." The line of sight is always a straight line from the eye through the scope to the target. The line of bore is also a straight line from the chamber through the bore to infinity. It's plain to see these two lines are always straight, but it's common to confuse the bullet's path, which is always a curved line, with the line of bore.
It's fair to say the bullet's flight path is a down-curving line from the rifle's muzzle; it falls faster as the bullet moves forward. Now, if the sights were aligned parallel with the bore line, it would be impossible for them to ever intercept the path of the bullet which is falling below the line of bore all the time.
I have to point out here that if this couldn't be remedied, the hunter would have to aim somewhere above the target on long shots. It would be a game of guesswork. Fortunately, this dilemma can be corrected by adjusting the sights so the line of sight intercepts the bore line instead of being parallel to it.
When we adjust the sights for longer ranges, the rifle's muzzle is tipped upward when the sights are aligned on the target. This causes the bullet to pass through the line of sight a short distance from the muzzle, travel in a curved line above the line of sight, and then fall through it at whatever distance the rifle is sighted in for. Note that the bullet never rises above the line of bore. Actually, the rifle is sighted in for two distances. One a few yards from the muzzle, the other where the bullet comes back through the line of sight.
The arc of flight is not a true curve; it's an elongated arc. A rifle sighted in for 250 yards may be two inches high at 100 and three inches high at 165. The bullet then begins a downward journey passing through the line of sight at 250 yards. The highest part of the flight is called the maximum ordinate, and it usually is around two thirds of the distance to the sight in point. With today's open terrain hunting, trajectory or the arc of the bullet is something every hunter should be concerned about. The popularity of the riflescope puts hunters on watches where very long shots are possible. It's almost a waste of time to take one of these stands with a rifle zeroed in for a 100 yards. Knowing the path your bullet follows, and sighting in to take advantage of it is a sure formula for success.