The underlying problem with quoted BC values or indeed 'real world' BC's is that in order to calculate it you have to assume the pellet is going to obey a specified drag profile.
The custom drag profile that CG uses has been named 'GA' - but you can edit your own custom profile to make a calculated trajectory fit your real world trajectory exactly.
BC is meaningless without knowing the drag profile used to calculate it and we're making the assumption that every shape of pellet has exactly the same drag profile which is unlikely, especially when you have a non-standard shaped pellet such as the H&N.
Try it in CG to see for yourself..
If we select the GA profile and enter MV as 760, Velocity at 50 yards of 600 - we get a BC(GA) = 0.0289
If we enter the same values but select the G1 profile we get BC(G1) = 0.0250
The BC will also vary based on the initial MV, you can often get a slightly better BC figure by dropping your MV a little bit.
So when any manufacturer quotes a BC value we're assuming that we can take that value and compare it against other pellets to tell us how flat the trajectory will be or how well it will perform in the wind, BUT we're making the huge (and probably incorrect) assumption that all other things are equal - such as drag profile and initial MV.
So in short - BC is an amalgamation of lots of variables - just quoting BC on it's own is meaningless.
Give me any pellet and I can get it to give me a BC answer of anything you like by varying other variables.