A scope with a Mil recticle and .1 Mil turrets will make this quest much more attianable. You don't have to spend thousands of dollars to get a scope that will work for you. There are pleny that are around or less than $500 that will work. In fact the optics for sale section is a fine place to look for a scope. Here's the short version of how to put all this together, if you were using your .308.
Find ammo the rifle shoots well. If you can't shoot it well, find someone that can.
Get the muzzle velocity of the projectile leaving the barrel, at least five shots, average them to one muzzle velocity.
Get the ballistic coefficient for the bullet. They are available all over the place. Sierra, Hornady, even Midway USA has the ballistic coefficients listed.
The MV (muzzle velocity) and BC (ballistic coefficient) are the two key numbers to plug into a ballistic calculator.
JBM is free and it is a very good calculator that provides very solid data. It will give you your trajectory in the Mils that your recticle and turrets speak in.
Read this website about how to "drive the rifle" as so many call it. Every facet that is mentioned is absolutely correct. Read "The Fundamentals of Marksmanship" over, and over until you have it memorized. It can be found in the Advanced Marksmaship unit. Which is one place you need to spend lots of time before you shoot a single round.