Re: true B.C s
Personaly I wouldnt. They are usually close and you could get away with it. Between any BC differences and atmosperic changes, you could be off enough to make a less than perfect shot. The problem with these preset knobs is that with air density changes and velocity changes from hot to cold temps you would be better off dialing in MOA's or Mils based on the current situation based on your targeting software.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.