(Posted in answer to another thread)
I don't know if anyone else uses this, but there's an interactive Java App. which opens up on the Norma website. The link for the English version is at:-
Select 'Ballistic US' which kicks it all off.
If you don't use the standard Norma ammo programmed in, you can alter it to the bullet weighti/coefficient you use, change the zero range, velocity, and other variables to get your whatever answer you need.
Give this a whirl - it's free