Re: 200 grain Accubond Nosler
I think the BC being higher is potentially a result of two things, first the higher velocities that long range shooters fire the bullets at, and also the quality of the barrels and machining in the crown area combined with better tuned loads allow the bullets to fly with less coning motion.
It is not true that CD is 1 to 1 corellated with the shock wave cross section dimensions, although it is a factor. It is true that drag can diminish, with a particular design as velocity increases.
I will not discuss the boatail design issues, or go detailed in a discussion on reducing supersonic drag although there are many books and research papers published on these subjects.