Manufacturers that use drops at their specific location, don't do favors to anyone, IMO. Like putting a hot rod car on the dynamometer and bragging it makes XXX horsepower and XXX torque. How does it work at my 7200 ft of elevation versus the sea level that it was tested at that have favorable conditions? Numbers will be so different as to be irrelevant. However, if ballistic coefficient is calculated from flight time which Barnes does, then atmospheric conditions can be accounted for and not guessed at.