In my effort of approximating drag constants for bullets, I have come across the McDrag program, by Robert L. McCoy. The disadvantage is that it approximates drag constants based on a few predefined shapes and a drag model (e.g. G1, G7), limiting it to only the simplest of bullets. Fully fledged CFD is beyond my level of knowledge and skill, but some level of CFD would probably be very useful, and certainly better than McDrag alone. I have been reading NASA's Beginner's Guide to Aeronautics (http://www.grc.nasa.gov/WWW/K-12/airplane/guided.htm) and other sources to learn of the various sources of drag in different flow regimes. Only the nonthermodynamic drag constant is of interest and below Mach constant 0.5 (or maybe even as low as 0.3) and above 5.0, the nonthermodynamic drag constant can be assumed to be constant. From what I have learned, the important sources of drag are: friction drag (skin friction) pressure drag (form drag) incompressible flow compressible flow wave drag Friction drag is determined by the boundary layer, viscous properties of the medium, and the wetted surface. Pressure drag is due to the pressure gradient over the body, arising from the fluid flow around the body. In compressible flow the change in mass density must be taken into account. Wave drag is due to the generation of shock waves over the body. For radially symmetrical projectiles (bullets), and with a very narrow field of required CFD, would it still be impractical/difficult to create a lean and efficient program to approximate drag constants of bullets over the range k_M=0.5(0.3)-5.0? Or would I ultimately resort to third-party, naughtily complex, messy, and bloated libraries/toolsets to accomplish my goal?