Can't speak to your tests as I wasn't there but the velocities especially at longer ranges will effect the BC. Also if looking for an average BC for long range then then the box number isn't the one to use. It's an average 200 yard BC to give people an apples to apples comparison with other brands. If you go to the Hornady page with their banded BCs and average the three bands that will work better at longer range.
Oh I know as they have no less than 4 different bc out there. Litz has it in the 320ish area for g7 which middle of the 2 lower numbers.