This paper conducts Delayed-Detached Eddy Simulation (DDES) of a guided projectile base flows. The inviscid fluxes are evaluated by the 5th order weighted essentially non-oscillatory (WENO) scheme with the low diffusion E-CUSP approximate Riemann solver and the viscous fluxes are calculated by second order central differencing. Time marching is performed with the second-order dual time stepping scheme and implicit unfactored Gauss-Seidel line iteration method in order to achieve high convergence rate. The accuracy of the DDES is validated with the force and moment experimental data. The DDES predicts the time averaged drag more accurately than the URANS and RANS. The primary difference of the drag prediction between the DDES and URANS is the pressure drag prediction in the base region. The DDES is demonstrated to be superior to the URANS for the projectile flow prediction due to more accurate base large vortex structures and pressure simulation.