Re: Need a long range ballistic program.......
With a medium caliber such as the 308 with moderate velocity say 2550 you can have a BC error of about .040 and still hit the kill zone of a deer. You will need accurate pressure (altitude if you cant get pressure), temperature, velocity, scope height and angle of fire. If you enter correct air density, then 90% of the time using a rough estimate on your BC will get you fairly close at 600 and under. With a flatter shooting cartridge, it will be more forgiving.
Bear in mind I dont advocate trying to kill game with an unverified BC. The point in this thread is to show the limits of ballistic calculators without verifying data. Its that 10% that will cause a wounded loss. ALWAYS verify before attempting to harvest game.
Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.