Telescopic lens are mounted ON TOP of rifles. How come they are accurate enough on target?

Question

Telescopic lens are mounted ON TOP of rifles. How come they are accurate enough on target?

Answer 1

you have to site it in to make it accurate.  duh.    

Answer 2

The margin of error between the scope and the bore are small, and the scope compensates for it.  Usually a rifle is sighted in to a nominal distance, so if it's set to 500 yds, then at 250 yds, the scope will be off on the high end (round is lower than aimed), and at 750yds, just the opposite.  But this difference is probably 1/2 inch off at most.

Answer 3

because you sight them in (adjust them) for a certain distance, then there are graduations in the sight to adjust for further or closer distances, and it takes a lot of practice.