ABSTRACTExperiments have been carried out by using small‐caliber projectiles for the determination of projectile penetration into brittle porous media. An empirical law for projectile penetration has been derived from these experiments, in which a .30‐caliber flat‐nosed projectile was used on four different target media that had ranges in permeability from 6 × 10−8cm2to 39,000 × 10−8cm2and Rittinger's numbers that ranged from 6.5 cm2/kg‐cm to 2