V50 / V0
The first criteria in measuring ballistic performance for body armor is the ability of the armor panel to prevent penetration of a ballistic projectile. For most users the key measurement is the velocity at which no bullets will penetrate the armor. Zero penetration velocity is referred to as V0.
Testing Body Armor for V50 performance determines the velocity at which 50% of bullets penetrate the armor and 50% of the shots are stopped.
V0 is difficult to measure effectively, so 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. The goal is to get three shots that penetrate that are slower than a second group of three shots that are stopped by the armor. These three high stops and three low penetrations can then be used to calculate a V50 velocity. 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.
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