posted a very usefull guide how to correcly use the various long-range weapons in Arma 2 on the BI forums
In this guide you can find the M24 Mil Dot Ranging and Correction Table, basic use of the ACOG scope, usage of the SVD Dragunov and the M203 Ground Impact ranges.
Quote Daniel_Malloy :
I have been searching the forums for range tables for the various long-range weapons in Arma 2, but to no avail. I have decided to start a thead in hopes that others will post their custom tables.
So, for all of you wondering how to use the available weapons and their scopes in ArmA2 and be able to hit something on your first shot make sure to check out the Arma 2 Weapon Ranging and Correction Tables topic