Re: Test for true BC\'s
It depends on what bullet your shooting and the drag curve it follows more closely, but it will work just like you decribe.
I found one thing I don't like about my handhelds balistic program, it uses only the G1 drag curve and does not give you the option to use any of the others or multible BCs as the Oehler program does. As a result many bullets will start to fly flatter at range than the program predicts when it follows fine out to 400 yards or so.
After you shoot out to 1000-1500 yards or so you should have an idea of what BC is working well through what distance ranges. For accurate charts I use 5 shot groups at each range interval to see a good group center.
In my experience the chart will deviate at longer ranges than actual drop using the G1 curve so the BC on the program will need to be modified to follow actual shot data. Very time consuming task but necessary, with many changing variables like temp, inclination angle etc they should be verified as well to be sure the program predicts drop accuratly with a different input changes. One reason to find a good bullet and stick with IT.