The Magnus effect on a generic 6.37 diameter long tangential-ogive-cylinder type projectile was studied by means of 3D Reynolds-averaged Navier–Stokes (RANS) simulations and wind tunnel measurements. The nominal Mach number was 3 and the Reynolds number, based on the model length, was 1.09 × 107. The simulations provided a profound insight into the flow structure and revealed a shift of the cross-flow separation lines as a consequence of the spin. This was shown to be the primary source of the Magnus side force for the higher angles of attack in the investigated range. The nonlinear dependence of the Magnus side force on the angle of attack was analyzed and reached a maximum value between 10 and 15 deg before decreasing again. The occurrence of secondary vortices in this range of angles of attack is presented as an explanation for a locally negative Magnus side force portion acting on the model.