One point concerning body armor I have always wondered is if the NIJ testing is done at shorter ranges. In theory shouldn’t armor offer higher levels of protection at longer ranges than the NIJ certification due to velocity loss (and with it, reduced energy)?
I know it’s not as simple as looking at energy, but a 240 Grain, JHP .44 Magnum round has about 700 ft-lbs at 25 yards, while a M193 round has the same energy at about 250 yards (according to my iSnipe app).
While a .44 Magnum projectile is a lot heavier, slower, with more surface area in the tip of the projectile compared to a .223 projectile, if for example the NIJ rating for a level IIIA plate or panel defeats a .44 magnum at near muzzle velocity, does it not stand to reason that, in theory, at extreme distance (say 400-500 yards) a piece of IIIA could similarly defeat a .223 round?
If so, hypothetical speaking, as JWR portrayed in his book Liberators, lighter armor might benefit a shooter with a long range .30 rifle engaging an enemy with a .223 rifle at 500-600 yards. – HTC
Hugh Responds: It is a complex issue, but the bottom line is that the armor penetration is determined by four basic factors:
- The energy in the round when it strikes the target,
- The surface area of the round striking the target,
- The material and construction of the round (lead core vs steel core, steel jacket vs copper jacket, et cetera), and
- The performance of the armor itself.
Obviously, the frontal area of a .44 round is considerably larger than that of a .22 round. Also .44 rounds generally do not have steel cores or steel jackets. Because of those differences, you can not just compare the energy contained in the rounds. To complicate matters further, at higher velocities, the rifle bullets can actually melt from the energy dumped into the target upon impact and the effect can be similar to a shaped charge with a molten jet of metal penetrating. It is NOT a safe assumption to make. Eventually, the distance involved will make the rifle round less effective at penetrating armor, but since you do not know the construction of the bullet nor the velocity it is fired at, along with a number of other variables, there is no practical way of determining how much distance is required to ensure your armor works.