I don't have an exact answer for the question about BC. Ballistic Calculators and chronys provide and get some good data, but the most accurate way to get drop data will always be going out shooting different distances and collecting it the old fashioned way.

I use strelok+ on my android phone and it's very good, but still had to adjust the data it was providing for my 308 when I got out passed 700yds. Of course there are many other variables that can play into the equation the further the distance is that you are shooting at.