*Editor’s note: NiJ ratings do not consider 5.56 in classifications. If something is rated level III it will stop .308 but not necessarily 5.56/.223.
Currently there are four common options for Level III plates:
5-6 mm steel (AR500/R50c/AR46100) plates: Level III steel plates offer a very thin profile, but are a bit heavier (6.5-7.5 lbs for a 10×12 plate) than some other options. They are very durable and offer inexpensive multi-hit capability against even closely spaced non-AP 7.62 x 39 mm and 7.62 x 51 mm projectiles, as well as for heavier 5.56 mm loads, including 62 gr M855 “green-tip”. Unfortunately, many lightweight (55 gr or less) 5.56 mm loads will defeat steel plates, including the extremely common 55 gr FMJ loads like M193. It is a VERY good idea to wear level IIIa soft armor underneath steel plates. *Spall is a great safety concern.
Hard compressed polyethelene (Dyneema/Spectra) plates: These are very lightweight (3-4 lbs for a 10 x 12 plate) multi- hit capable level III plates that will stop closely spaced hits of both the lightweight 5.56 mm ammo that defeats steel, along with the 7.62 mm threats stopped by steel, as well expanding rifle ammunition in many hunting calibers. Unfortunately, hard polyethelene plates are often perforated by current military issue 5.56 mm 62 gr M855 FMJ “green-tip” and 5.56 mm M855A1 62 gr ammunition. While not necessarily required, it is not a bad idea for compressed polyethelene plates to be worn in conjunction with soft level IIIa armor underneath.
Non-ceramic hybrid plates: These combine several non-ceramic materials, for example both steel and hard polyethelene layers, and appear to offer the most robust protection of any current level III plates. They are very durable and stop multiple closely spaced hits of almost all non-AP ammo, including high velocity 5.56 mm threats, as well as M855; however they are typically a bit heavier (7-7.5 lbs for a 10 x 12 plate) than some other types of hard armor. These are typically NIJ stand- alone capable, so soft armor is usually not required underneath. These plates typically are quite durable and generally do not require annual non-destructive testing.
Ceramic plates: These plates are relatively lightweight (4-6 lbs for a 10 x 12 plate) for the protection provided, but can be more susceptible to occult damage in day-to-day use, and usually cannot withstand as many closely spaced hits as other plate types. Ceramic plates should ideally undergo non-destructive testing (x-ray, ultrasound, etc…) each year to ensure that hidden cracks are not present. Ceramic plates are available in both in-conjunction and stand-alone configurations. Note that almost all level IV plates use ceramic elements in order to stop AP rounds.
Ceramic hybrid plates: Most ceramic hybrid plates combine ceramic materials like silicone carbide, aluminum oxide, or boron carbide along with various other materials, including metal, compressed polyethelene, etc… These plates are often heavier than pure ceramic plates, but are a bit more robust, with potentially better multi-hit protection and greater durability. Nonetheless, periodic non-destructive analysis is recommended because of the ceramic elements. Ceramic hybrid designs are often used in stand-alone level IV plates intended to stop AP projectiles.