I have watched intently as a variety of discussions have drifted toward a single question: Do we really know how BC and wind drift interact? Background: In reading several volumes written by Bryan Litz, I've found that the operative method for determining BC is to plot the drag function by measuring the residual velocity at varying distances from the muzzle (Doppler, downrange chronograph, etc.). By assessing the residual velocity, a model is created of the bullet's velocity retention behavior. From this model, the BC of the bullet is derived. The theory on wind drift, as calculated by many ballistic calculators, is that the lag time determines the wind drift. However, there are a number of substantial accounts of bullet behaviors that do not follow the lag time model. Some theorize that the bullet mass is an unaccounted for component of the bullet's wind-drift performance. I might suggest one more variable - wetted area. Since it is virtually impossible to fire a bullet over a long distance and have adequate datapoints as to the exactly air velocities all along the range, comparative testing seems to be the only way to economically ascertain the actual differences between bullets. Is anyone doing, or has anyone done real-world, side-by-side , simultaneous fire testing?