a second concept has been developed in ballistic testing called V50. This is the velocity at which 50 percent of the shots go through and 50 percent are stopped by the armor. US military standards define a commonly used procedure for this test. The goal is to get three shots that penetrate and a second group of three shots that are stopped by the armor all within a specified velocity range. It is possible, and desirable, to have a penetration velocity lower than a stop velocity. These three stops and three penetrations can then be used to calculate a V50 velocity. In practice this measurement of V50 often requires 1–2 vest panels and 10–20 shots. A very useful concept in armor testing is the offset velocity between the V0 and V50. If this offset has been measured for an armor design, then V50 data can be used to measure and estimate changes in V0. For vest manufacturing, field evaluation and life testing both V0 and V50 are used. However, as a result of the simplicity of making V50 measurements, this method is more important for control of armor after certification. Cunniff analysis Using dimensionless analysis, Cuniff arrived at a relation connecting the V50 and the system parameters for textile-based body armors. Under the assumption that the energy of impact is dissipated in breaking the yarn, it was shown that Here, are the failure stress, failure strain, density and elastic modulus of the yarn is the mass per unit area of the armor is the mass per unit area of the projectile Military testing After the Vietnam War, military planners developed a concept of "Casualty Reduction". The large body of casualty data made clear that in a combat situation, fragments, not bullets, were the greatest threat to soldiers. After World War II vests were being developed and fragment testing was in its early stages. Artillery shells, mortar shells, aerial bombs, grenades, and antipersonnel mines are fragmentation devices. They all contain a steel casing that is designed to burst into small steel fragments or shrapnel, when their explosive core detonates. After considerable effort measuring fragment size distribution from various NATO and Soviet Bloc munitions, a fragment test was developed. Fragment simulators were designed and the most common shape is a Right Circular Cylinder or RCC simulator. This shape has a length equal to its diameter. These RCC Fragment Simulation Projectiles (FSPs) are