Posts Tagged ‘hard armor’

The final class of materials for use in rifle plates is a familiar face- UHMWPE. Despite its drawbacks in soft armor format, in hard/rigid applications, this material does not show as many weaknesses. For reasons that are still not fully understood, the heat tolerance of PE hard armors is much better than soft armors (showing a danger zone of 195-200 degrees F rather than 180 F). This may be due to the typically thicker profile, thus providing a larger thermal mass to heat (taking longer and requiring more ambient heat to achieve irreversible denaturing). Also, contact shots are not as likely to have such a high risk of penetration due to the physical properties of a rigid defense compared to a flexible.

In addition to finding wide application as the backing material in many (if not most) ceramic plates (and a VERY effective steel/UHMWPE hybrid by Armored Mobility, the TAC3S), it is also used as the sole material in a significant number of plates by various manufacturers. In a hard armor format, UHMWPE offers some notable advantages: it is positively buoyant (it floats), is immune to acids, zero spallation/splash, and makes for the lightest rifle plate available. The drawbacks are moderate-high cost, and the thickest profile of any rifle plate (some have likened it to wearing a Wheaties box on your chest). In addition, UHMWPE plates typically do not stop M855 Green Tip ammunition, while having no difficulty with M193 (the opposite of most steel plates).

UHMWPE plates stop rounds by means of frictive braking. The fibers of UHMWPE squeeze and apply compressive braking force to rounds that strike. Generally the projectile is embedded about halfway into the armor when it is stopped. This leads to no splash or spallation, since the round remains mostly intact. M855 is thought to penetrate due to the incompressibility of the steel penetrator. Regardless of the mechanism, it is important to take into account when considering potential threats.

Due to their properties, some applications (maritime, swimmers) tend to benefit from their use. If the thicker profile is not a hindrance, they can be quite effective. As always, assess your needs and potential threats before making a decision.

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As we transition from our overview of soft armor, the microscope is focused on the question of rigid defense. An interesting side note is how much history reflects the current situation when it comes to protective gear. Typically, a man-at-arms from the 14th century onward would wear a maille, garment (byrnie (shirt) or hauberk, coif, and sometimes leggings), with hard defenses over the top. Today, the same system works well, with soft armor providing the correlate to the maille, and hard/rifle armor standing in for the plate defense.

When considering modern rigid armor, it is important to have a thorough understanding of threat level ratings and the needs of the end user. There is a common misconception that ALL hard armor will provide protection against centerfire rifle rounds. This is far from the truth. Rigid trauma plates have been utilized in concealable soft armor for decades, typically made of steel or titanium. While some of these legitimately increase the threat level rating of the armor they are worn with (and some are even standalone rated themselves), they do NOT give protection from rifle fire.

Hard plates stop projectiles using a different mechanism from soft armor (which must only contend with pistol rounds). When soft armor is hit with a round, the fibers interact with he (relatively) large frontal area. Like a net, these fibers catch, slow, and stop the round, absorbing the kinetic energy by elongating (very slightly), and “fiber pullout.” The later is very similar to “playing” a fish on a fishing line. By allowing line to pay out, under drag, the fish is depleted of energy. The more fiber pull-out force is applied to the round, the more efficiently it is stopped.

Rifle rounds, because of their narrow cross section, do not engage enough of the fibers for them to apply a stopping force. Centerfire rifles will not even “see” soft armor. Hard plates are required, and stop rifle rounds using three distinct methods (sometimes a combination of two of three): mushrooming/deforming, shattering/yawing, and frictive braking. Different material plates have different effects, and we will look at specifics in later posts.

There are some specific plates that will stop lead core 7.62X39 rounds (The Second Chance K-30 plates specifically), but my personal recommendation is thus- if you are wearing rigid plates larger than 6″ X 8,” they should be rated a minimum of level III.

A side note is neccessary- for some time, with increasing frequency of late, manufacturers have started releasing level IIIA hard plates. I am lukewarm on these, for the simple reason outlined above. IF YOU ARE WEARING RIGID PLATES, YOU MIGHT AS WELL DERIVE RIFLE PROTECTION. The only scenarios that these plates would be appropriate might be if you were fairly certain that rifle rounds would not be encountered, or if you were looking for a moderately concealable plate to protect you against blunt force trauma (bats, fists, knives) over and above what your normal concealable armor provides.

About those ratings. NIJ ratings are the most commonly encountered, and can be somewhat confusing. Level IIIA is a soft armor rating, and provides protection from hot .44 Magnum and 9mm subgun rounds (typically at velocities found in 16″ barrels). Level III is a rifle/hard armor certification, and the spec is: 6 rounds of M80 ball at 2750 fps, fired at a distance of 15 feet, striking within a 6″ circle. To further confuse the issue, manufacturers generally specify whether the armor is “ICW” (In Conjunction With), or “standalone.” ICW requires soft armor (usually level II or IIIA) to be worn behind the plate in order to meet the full spec. This can be for several reasons- first off, ICW plates can be thinner in profile, usually sacrificing some of their backing material (usually a rigid aramid or UHMWPE composite). Secondly, ICW plates may not make their BFD (backface deformation) numbers without some additional padding behind the plate. Finally, the ICW plates may occasionally have issues with backface spall/break through (rounds that either transmit enough energy to cause ejecta, or barely penetrate).

What this means is, if it says ICW, believe it. Wear soft armor behind your plates. I go one step further, and recommend you wear soft armor behind ALL hard plates, even stand alone. The reasons for this are: the added weight and bulk of 4th and 5th generation woven p-aramid plate backers is negligible, and having the extra padding (in the event of a ballistic strike) will be MUCH appreciated after the fact.

Level IV plates exhibit a higher nominal rating than level III plates, but many make the mistake of assuming that they are “better.” Better, as always, is subject to the requirements of the end-user. The spec for level IV plates call for stopping ONE round of M2AP Black tip, at 2800 fps, 25 feet from the muzzle. There is no requirement for more than one round, so hypothetically the plate could stop the round and disintegrate into a fine powder (generally, they won’t). IF you expect to face AP threats, then IV makes sense. But if you only anticipate standard lead or mild-steel core threats, III makes more sense (and usually is more cost-effective).

Also, it is important to note the specs. PAY ATTENTION to the specs, as some rounds that should be “expected” to be stopped will penetrate. III is M80 ball, IV is M2AP. Manufacturers will often include an addendum to the certification if they have bench/proof tested other rounds over and above the NIJ rating. More details forthcoming in future posts.

Next, we will look at the various plate materials, their relative benefits and drawbacks, and how you can choose the best for your intended use.

Stay classy folks.

Note: edited to add more material