The basis of this work is to find how varying the grain size of materials contained in sandbags (sand and crumb rubber) effects the ballistic penetration of the projectiles from both the 7.62x39mm (308-short), and 9mm Luger cartridges. The sandbags were stacked in a pyramidal stacking configuration according to military specifications in order to simulate a section of a sandbag barrier or redoubt as would be seen on the battlefield. The projectiles were fired at the targets, and the velocity and penetration data was recorded. The results concern both military and civilian applications alike. The 7.62x39 round was found to experience more fragmentation as grain size increased, and was also found to have, on average, the least amount of penetration into the largest grains. The 9mm round was found to suffer negligible deformation in all of the various sizes of materials, and when fired at the two types of materials, showed a steady trend of decreasing penetration depth with increasing grain size. The sand had a wearing effect on the projectiles leaving them scared or fragmented and deformed while the rubber kept the rounds in pristine condition.