If you would like to find the drop at a range for some type of gun use this
Drop = (Distance/Velocity)*(Gravity*GravityModifier)
so velocity for most guns could be said to be around 800m/sec (if you want to calculate the drop better look in the guns tweak file to find its velocity). Bf2 gravity is 14.86m/sec afaik, and rifles use a gravitymod of 0.3, snipers a mod of 0.1.
also I made a range card for the m40a3 in another thread and iirc the drop at 1000m was about the size of a person in bf2, so you just needed to aim a players hight above the target@ 1000m.