Steel has been the material of choice for body armor for centuries, ever since the method for hammering out large, uniform sheets of bloomery iron was rediscovered in the 13th century. Today, advances in steel technology have continued to made this material viable as a protective material.
Steel plates find use in concealable armor as trauma plates, generally having a thickness of 1-3mm. These plates can provide everything from trauma-only, to standalone IIIA protection. Sizes range from 5″ X 8″ to 8″ X 10″. There are a few notable “in between” plates, such as the Second Chance K-30, which will stop 7.62X39 soft core.
Today, most steel plates will be of the “rifle” persuasion. It is important to note that currently, ALL steel rifle plates for personal protection are level III at the highest. Steel plates that will provide level IV (AP) protection are prohibitively heavy for use as wearable armor.
It is important to remember that level III spec calls for protection vs. 6 rounds of M80 ball @ 2750 fps. This means that many round can (and have) been able to defeat level III steel. A few years back, a minor scandal erupted when plates from a well-known manufacturer were found to be easily penetrated by M193 ball above 3000 fps (ironically, I had experienced this same phenomena a week prior to this revelation, and chalked it up to a bad batch of steel. M193 exceeds the shear strength of AR500 steel, and will cause shear-plug failure in the plate. Think a paper hole-puncher, but with steel. The full mechanism of why/how M193 penetrates steel armor is not fully understood, but there are several working theories (to be expounded upon later).
The upshot is, make sure when you buy steel plates, they have either been subjected to additional proof/bench testing, or do not trust them to stop anything but M80 ball.
Steel plates are nearly always sold as “ICW” (In Conjunction With), but I *ALWAYS* advise wearing soft armor behind them. This is for additional blunt force trauma protection, as well as catching any back face spallation (a possibility with all rifle plates).
Steel for rifle armor typically falls into a very specific hardness range, generally 500-600 Brinell (which is VERY hard as far as steel goes). AR500 (“Abrasion Resistant,” 500 Brinell) is the most commonly used commercial steel for rifle armors. It has good uniformity, low cost, and works fairly well.
There are a few other options regarding steel plates, specifically Bainitic steel, and HHS (High Hardness Steel). Bainitic steel utilizes a special heat treating process to produce a particular crystalline phase within steel, called Bainite. This material acts as reinforcement to the crystal lattice of steel, rendering it stronger and tougher than normal quenched/drawn steel plate. At this time, it is still not widely used in personnel armor, though it has found growing use in vehicular armor. Bainitic armor is an excellent choice for personal armor, though the price is typically about 1.5 times higher than normal AR500.
HHS is another option, and describes steel that is hardened to 600 Brinell or above. This allows it to be made thinner than AR500 while having greater ability to stop projectiles. It does have issues with cracking due to its extreme hardness, and is approximately twice as expensive as normal AR500 steel.
Steel plates are extremely durable, often capable of absorbing tens and even hundreds of hits while still retaining ballistic protection properties. With no fragility issues, steel plates are a good choice for use in scenarios calling for extreme ruggedness. With their thin profile (unless coated with a polymer/elastomer finish), they make a good choice for concealable/PSD use. Steel plates are also the most affordable/cost effective rifle armor solution.
One of the biggest drawbacks of running steel plates is their heavy weight. Most 10″ X 12″ steel level III plates weigh around 8 lb. EACH. There is also the issue of rust and corrosion. Finally, as has been discussed before, steel plates suffer from front face splash/spall. Projectiles stopped by the armor will splatter, sending clouds of high velocity core and jacket fragments at a 90 degree angle to the impact. This endangers the wearer’s face, throat, and extremities, and precautions need to be taken by the wearer (https://drmorgear.wordpress.com/products/spall-guards/).
In closing, it is important to evaluate your needs, and determine if steel plates are the correct choice. Next time, we will look at ceramic plates.
Stay safe!
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