A comparative experimental study of ballistic performance of armour-piercing hardened steel core projectiles on steel targets

Standardized testing protocols are widely used in the qualification of armour systems, associating each protection level with a specific projectile type and test conditions. While standardized testing aims to ensure consistency and repeatability, it also implicitly assumes that the standardized projectile conservatively covers the ballistic performance of all projectiles of the same calibre and core type. However, differences in core geometry, material composition, and manufacturing quality between projectiles from different manufacturers can significantly affect performance. Therefore, the objective of this study is to quantify how projectiles of the same calibre and core type, but from different manufacturers, perform relative to the projectile prescribed by a standard, and correlate the underlying projectile characteristics responsible for performance differences. To this aim, ballistic tests were conducted with various 7.62 mm × 51 armour-piercing hardened-steel core projectiles under normal and oblique impact conditions against armour steel targets of different thicknesses. The projectile cores were characterized via measurements of hardness, mass, geometry, and quasi-static compression. The results demonstrate that projectiles of the same calibre and core type can have significantly different perforation capabilities. Notably, the best-performing projectile under normal impact conditions was not the best under oblique impact. Furthermore, projectiles which produce large depth of penetration were shown to not necessarily produce high penetration probability. These results highlight the limitations of relying on a single standardized projectile to represent the most severe threat within a calibre class for armour certification.