Terminal ballistics of 7.62 mm armour piercing projectiles against spaced, oblique RHA plates

Spacing and obliquity, when used together, are known to provide one of the most weight efficient solutions for armor protection. Although this configuration has been widely used over almost 100 years there is little quantitative or design data for such systems. In the present study a series of tests were performed using a steel-cored 7.62mm bullet (DAG 7.62x51) against RHA plates of varying thicknesses, spacing and obliquity of the front plate. This work showed that front plate should be substantially thinner than the rear, a ratio of 0.48:1 gave the best results. The highest mass efficiency (2.00) was for a large spacing (400mm) but this could be reduced to 50mm with only a 17% reduction in ballistic efficiency if a slightly more oblique front plate was used.