Computational evaluation of assembly technique influence on ballistic performance of a bullet – non-linear relation between méplat size and the drag coefficient

The continuous development of production and assembly techniques gives rise to the idea of following a new approach in the small-arms ammunition design process. Commonly used intermediate cartridges were designed over 60 years ago, and their construction and assembly processes are not significantly different than what was available almost a century ago. Along with the recent development of individual protection devices and with the general availability of modern ballistic plates utilized in plate carriers type of individual armor, it sparks the necessity of designing a new, intermediate cartridge, using new assembly and technology methods. The vital aspect of the ammunition design process is a determination of the materials utilized in bullet elements and its assembly method. Therefore, there is a necessity of evaluating if different assembly techniques can provide the improved ballistic performance of a bullet. The paper includes a comparison of two differently assembled projectiles with steel penetrators: a standard Full Metal Jacket and a reverse-drawn Semi-Jacketed bullet. The designs were evaluated in terms of their external ballistic performance for specific initial conditions using 2D Computational Fluid Dynamics simulations and, separately, with a semi-empirical method. The paper aimed to assess the influence of the assembly method on the bullet’s external ballistic performance. Both calculations revealed a nonlinear relation between the projectile méplat diameter and the coefficient of drag, which indicates a limit where the méplat size reduction is beneficial. The results implicate a perspective bullet construction that would provide the user with better external ballistic performance, more consistent and precise than a standard Full Metal Jacket design.