Re: Drop Chart Questions
Unfortunately, my experience mirrors yours. Computer drop charts don't work that well for simple reason that the parameters we enter are not correct. BC, scope height, and weather conditions will affect the data. Since most of these parameters vary from gun to gun, and day to day, there will always be some error.
I generate a computer chart so that I am in the ballpark then shoot to finalize. By using "my" drop chart, I shoot during different weather conditions to confirm. Usually am very close to my data (plus or minus a click or two).
At the ranges you are shooting, the weather conditions will not matter as much as temp. changes and its affect on muzzle vel and accuracy. Doing load development in the spring then shooting in the summer can give you different results. I avoid this by using Hodgdon Extreme powders. They are temp insensitive and seem to provide very consistent vel over a large temp change.
Get a good rangefinder (I like Leica) and work out your table. Enjoy the shooting.