The ballistic limit or limit velocity is the velocity required for a particular projectile to reliably (at least 50% of the time) penetrate a particular piece of material. In other words, a given projectile will generally not pierce a given target when the projectile velocity is lower than the ballistic limit. The term ballistic limit is used specifically in the context of armor; limit velocity is used in other contexts.
The ballistic limit equation for laminates, as derived by Reid and WenSR Reid, HM Wen. "Perforation of FRP laminates and sandwich panels subjected to missile impact". In: SR Reid, G Zhou, editors. "Impact behaviour of fibre-reinforced composite materials and structures". Cambridge: Woodhead Publishers Ltd. 2000. In: G Reyes Villanueva, WJ Cantwell (2004). "The high velocity impact response of composite and FML-reinforced sandwich structures". Composites Science and Technology 64:35-54. . is as follows:
where is the ballistic limit is a projectile constant determined experimentally is the density of the laminate is the static linear elastic compression limit is the diameter of the projectile is the thickness of the laminate is the mass of the projectile
Additionally, the ballistic limit for small-caliber into homogeneous armor by TM5-855-1 is:
where is the ballistic limit velocity in fps is the caliber of the projectile, in inches is the thickness of the homogeneous armor (valid from BHN 360 - 440) in inches is the angle of obliquity is the weight of the projectile, in lbs
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