Semi-empirical methods are often used in the preliminary design stage for quick estimation of aerodynamic coefficients for conventional ammunition. Generally, an aero-data prediction from the semi-empirical method is relatively more accurate and fast. The present work is about exploring the possibility of applying the semi-empirical method to non-conventional geometries. Aerodynamic coefficients were generated using the projectile design and analysis system (PRODAS) tool, which is a well-known semi-empirical method, and computational fluid dynamics (CFD) in the subsonic flow regime. The results from PRODAS indicated that the ammunition exhibited an aerodynamically stable geometry, indicating favorable flight characteristics. When a detailed CFD analysis was conducted using Ansys Fluent, ammunition exhibited aerodynamic instability under similar flow conditions. Therefore, this study shows that aerodynamic coefficients estimated using the CFD method for non-conventional geometry at the preliminary design stage are more precise than those estimated using the semi-empirical method and save time for later stages of design.