John S. is a guest writer who is concentrating on the subject of body armor. This is his second article on TFB, his first one being

For simplicity sake, I’m not going to go too in depth as it can be rather confusing. This also isn’t a blanket guide, different manufacturers use different blends of materials and can in turn produce plates with very different threat ratings. I’m not going to talk too much about the different composites and blends as there’s too many.

• Ceramics.
  Often in the form of a composite blend, one of the most common Ceramics used in plates currently is Alumina Ceramic (Aluminum Oxide). Now often lots of Ceramic plates have a Dyneema/ Polyethylene or Kevlar blended back. This is mainly just for reducing blunt force or acting as a backer for the bullets.

Currently the US Military’s ESAPI plates are made of Boron Carbide (Type of Ceramic), which allows it to have a higher threat rating, at a lower weight. ESAPI is a military rating and generally you will not find civilian plates made of Boron Carbide to ESAPI specifications. The only civilian ESAPI I know of is made by bulletproofme.com and costs $460-640 per plate (depending on the size).
Generally, the pro’s of Ceramics are its weight they are generally lighter at around ~6.5-8 pounds, their ability to withstand AP threats and they do not produce dangerous spall when hit.
However the cons are Ceramic must not be regularly rough handled, I mentioned Ceramic is not like glass, but don’t toss your plates around or toss them on the ground. They are especially susceptible to damage when dropped on the edges.

Exception: As I mentioned before, not all armor is created equal.
RMA Armament produces Ceramic plates model #1189 that are not fragile and are rated up to 6 rounds of .30-06 M2-AP.

• UHMWPE (Ultra High Molecular Weight Polyethylene) (Or Polyethylene or Dyneema)

For our purposes here, we are talking about PURE Poly plates, I will talk about these composites shortly.
This is a type of ballistic polymer, a type of molded resin. Therefore, it has the properties you would find in a polymer.
These plates are generally going to be the lightest and or thinnest level 3 plates available. However, that does not come without a cost.
A pure Polyethylene plate can be defeated by a single round of M193 or M855. It would pass through the plate quite literally like a hot knife through butter. (Think hot fast metal against plastic).
Heat and Cold can also be an enemy of Polyethylene plates. When exposed to extreme heat (think Texas summer in the trunk of a car) the plate can become soft and warp, which in turn decreases the ballistic effectiveness. When exposed to extreme cold (think winter in Maine) the plate can become brittle, which also decreases the ballistic effectiveness. (-15F to 150F)

Again, keep in mind this is not a blanket assessment, not all plates are created equal and not all manufacturers make the same plates.
Polyethylene composite plates are less susceptible to the weaknesses of pure Polyethylene. This again depends on the manufacturer and what kind of composite.
Its very important to look at the rounds that the manufacturer has tested outside of NIJ requirements when choosing a Lightweight Polyethylene plate.
Poly composite plates are also heavier, due to different materials such as ceramics or metals being added in.
When in doubt, email or call the manufacturer to make sure.

• Steel armor (AR500, AR650, MIL-A 46100, etc)
  Steel armor, the cheapest and heaviest of them all. I personally have a strong dislike for steel armor, but I am here to provide facts. How you choose to spend your money is none of my concern. However, I will not be recommending any steel plates today.
  
  First off there are several types of steel armor, but the properties are going to be roughly the same. Its steel, even if you change the hardness or composition, the fruit isn’t going to fall far from the tree, the physics are similar.

The numbers after “AR”, whether it be 400, 500 or 650 is just denoting the hardness of that type of steel. As you know… harder steel may be brittle, and the other way around it may be soft.
MIL-A 46100 is a Mil Spec or “military grade” steel that was designed to be used on armored vehicles or to fortify structures.

Let’s start off with the pros of steel since it’ll be short.
1) Can be multi-hit capable. AR500 plates can take a beating, as traditionally they were used as shooting targets. They can be struck in the same place twice generally without issue.

2) Low-visibility/ concealment. Steel can be thin, yet stop rifle threat rounds, hence its usefulness in concealment scenarios. However, Ceramic/ Polyethylene technology has reached a point where steel is obsolete for this role.

Now with the cons,
1) Can be vulnerable to high velocity threats such as M193 or M855 fired at a high velocity. Mainly FMJ and steel core/ penetrator type ammunition.
(Example, AR500 Lvl 3)
https://www.youtube.com/watch?v=oMYkEMhPsO8&t=1s

2) Spalling is a major concern for all steel armor. Since steel is hard, when a bullet impacts the strike face, it will explode into shrapnel and fragmentation.
The spalling that is generated from bullets striking steel armor generally runs along the face of the plate. Which means fragmentation is likely to go into your chin, arms and legs/ groin if you are crouching.
Pretty much all steel armor is now sold with at least one build up coat of spall liner (Rhino, Line-X, etc). However, a single coating generally does very little for spalling and is best for one or two rounds.

3) Ricochets.
Ricochets are another concern when it comes to steel armor, if a round hits at an odd angle, it may travel along the plate and go into one of your arms or legs.
Due to the hardness of steel, they are more prone to ricochets than Ceramics.

4) Blunt force trauma/ energy transfer
Rifle rounds have a tremendous amount of energy and force behind it. Steel is a rigid and hard material, when a bullet strikes it, the energy will “pass through” the steel and into the chest of the wearer.
If the plate is struck at the right place, depending on how strong your bones are, it may break your sternum and puncture your heart.
A few rounds to the chest could even equal heart stoppage/ internal bleeding.
Ceramics work like a “net” where the ceramic breaks and catches the bullet, also dissipating some of the kinetic energy, though not all of it, it is less severe than steel.

5) Weight
This is an obvious one, a 10×12 Steel plate is 8.4 pounds with two buildup coats of spall liner. Then more with trauma padding (seriously shouldn’t wear them without).
Steel plates weigh as much as the heavier end of Ceramic plates, but has a level 3 rating and many disadvantages along with it.

How you choose what armor you require is up to you. Armed with this knowledge hopefully you can make an informed choice. I always urge you to do more research on your own.
Before choosing what armor is best suited for you, you should ask yourself these questions and be honest when doing so.

1) What is the REALISTIC threat you are facing? Do you really need the bulk and weight of AP protection if you’ll never face it?

2) What realistically do you need more? $400 in training? Or $400 for a set of plates “when it hits the fan”?

3) Is saving $200 more important than getting quality armor if you truly NEED it?

Choose a quality brand:

When it’s time to buy the armor, make sure to choose a reputable brand.
The following are some good brands to buy from and some of their choices.

1) Velocity Systems:
You cannot purchase directly from Velocity Systems unless you are MIL/LE/GOV.
-PSA Level 4 Standalone (10×12 Swimmer) $304 Each (US Elite) or $320 (AT Armor)
2) AT Armor:
-FFS4 Level IV Standalone Special Threat Tested (SAPI Cut Sm-XL, Shooters cut 10×12) $185 Each
-STOP Plate (See website for rating) (SAPI Cut Sm-XL, Shooters cut 10×12) $430 Each
3) Hoplite Armor:
-Level IV 10×12 Single Curve Swimmer Plate $150 Each
(Hoplite makes great rifle threat rated shoulder plates too, one of a kind)
4) RMA Armament:
-Model #1155 (10×12 Single Curve SAPI Cut Level IV Standalone) $135 Each
-Model #1189 (10×12 Single Curve SAPI Cut Level IV Standalone) $300 Each
(Non-Fragile and multi-hit .30-06 M2-AP
5) Highcom Security:
-Guardian 4SAS7 (Level IV Standalone, Sizes vary from XS-XL, side plates, SAPI cut, Swimmers cut, Square, etc) $160-230 Each (Chest) $130 (Side).

6) Ceradyne:
The manufacturer of the current US Army issued ESAPI plates. Most of their armor is not available for purchase to the general public but much of it is legal to own if you find it.

Sources:

1. National Institute of Justice 0101.06 Standard:
   https://www.nij.gov/publications/Pages/publication-detail.aspx?ncjnumber=223054
   (PDF) https://www.ncjrs.gov/pdffiles1/nij/223054.pdf
   -pg. 4 (Level III/ IV testing parameters)
   -pg. 36 (Drop testing)
   -pg. 49 (Back-face deformation)

1. MIL-A 46100 D Standard:
   (PDF) http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-A/download.php?spec=MIL-A-46100D_INTERIM-AMENDMENT-2.020498.PDF
   -pg. 22 (MIL-A 46100 D .30 cal testing @30 degrees)

1. SAPI/ ESAPI approximate ratings:
   http://bulletproofme.com/Body_Armor_Accessories_Rifle_Protection.shtml

Polyethylene Plates weakness against AP/ Heat & Cold

http://www.bulletproofme.com/RP-Polyethylene.html

Further Reading/ information:

If you’re interested in more of this, here is some more reading to do and some videos.

1. NIJ 0101.06 Standard (One of the sources for this article)
   https://www.ncjrs.gov/pdffiles1/nij/223054.pdf

Shooting test for a Level IV plate:
https://www.youtube.com/watch?v=4vL-08x7T4I (Skip to 2:10)