The "SPherical" standard projectile will, of course, be suitable for the black powder lead ball bullets and also lead shot from shotguns.
The drag function in the trans-sonic zone changes dramatically for ball sizes above about 0.6 inches, but should be fine for anything smaller. The supersonic drag function will be fine for any size ball.
The program uses second order polynomial drag functions, which were fitted to the drag table data produced by Francis Bashforth and is published in the "Textbook of Small Arms", 1929. Those functions are as follows: