In this report, we evaluate the radar cross section RCS of in-flight ballistic projectiles rockets, artillery rounds, and mortars by taking into account the relative position and orientation of the targets with respect to a ground-based radar. The evaluation is based on computer models of both the ballistic trajectory and the radar scattering from the targets. Extensive theoretical derivations are developed, followed by numerical examples. We consider 2 types of projectiles a 155-mm artillery round and a 120-mm mortar, as well as 4 radar frequency bands L, S, C, and X. Using simulation tools entirely developed at the US Army Research Laboratory, we analyze several sample scenarios and discuss the phenomenological findings associated with them. The in-flight projectile RCS calculations will be used in future studies of radar system performance evaluation.