Re: BC issues
I know some Mfgs fudge or over-estimate their BCs.
But if Bryan Litz publishes a BC, I'd think twice before adjusting it much, if at all. Individual rifles may affect BC, but it's not by very much.
On the other hand, chronographs are usually fairly precise as to the relative shot to shot velocity provided conditions don't change. But, the accuracy (magnitude) of the measurement can be off by quite a lot.
Keep us posted.