The supersonic aerodynamics of a high spin armor-piercing fin-stabilized discarding sabot projectile (APFSDS) is numerically and experimentally investigated. Classically, using a 120 mm smooth bore gun, the value of the nondimensional steady spin rate of the inflight APFSDS projectile is about 0.01. In our case, a medium caliber APFSDS projectile is fired using a rifled barrel gun. The initial nondimensional spin rate, which is, with the Mach and the Reynolds numbers, the third similitude parameter governing the projectile aerodynamics, is significantly greater and about 0.09. Complex aerodynamics and flight dynamics were found and are detailed in the paper. In particular, the side force and moment evolutions with spin rate and angle of attack reflect a highly nonlinear behavior of the Magnus effect. The numerical predictions are mainly based on Reynolds-averaged Navier–Stokes (RANS) and URANS (Unsteady RANS) equations. Flight tests have been performed in an aeroballistics corridor. The exterior ballistics of the projectile was investigated using a yaw cards method, the experimental results are analyzed using a 6DOF flight dynamics model. The comparison between computational fluid dynamics (CFD) computations and flight tests results is satisfactory. CFD computations show, for the first time at our knowledge, that a roll-pitch coupling may appear.