Homer Powley's "Secant Boat Tail" projectile is the same as the Aberdeen Proving Ground G7 projectile, having a 10 calibre radius secant type nose and a 7.5 degree boat tail. This efficient shape is very similar to the "high BC" target bullets being produced by a number of bullet manufacturers these days. Indeed, a number of bullet manufactuers such as Berger and Hornady are now giving G7 ballistic coefficients for their secant nosed, boat tailed target bullets as well.
The program uses second order polynomial drag functions, which were fitted to the drag table data, to calculate the drag for a given velocity. Those functions are as follows: