AR400 vs. AR500 Plates: Which is the Better Protective Material?

Safety is one of our most basic needs.  You need to know that the body armor you are strapping on is the right one.  It can be a life or death choice, so you have to be informed.  Not all body armor is made equal, and you owe it to yourself to take the time to get the right information and make the right decision. AR500 plates are better at protecting you than AR400 plates because the steel in the AR500 plates is a harder and tougher material.  It is far less likely to bend or break under the pressure of an incoming projectile.

In this article, we will explain in-depth why AR500 plates are superior to AR400 plates.  We will then go into what makes a good vest and how to choose the right vest.  We will also compare some popular vests on the market to give you a breakdown of their attributes so you can make an informed decision.

Which is the Better Protective Material?

The AR in AR500 and AR400 stands for Abrasion Resistant.  This is a specially formulated type of high-carbon alloy steel that has been carefully and specifically designed to have greater hardness.  AR steel plates are extremely durable, offer impact resistance, and work well in harsh applications. AR steel is used in everything from mining and construction to making body armor and sniper rifle targets.  Mining and construction equipment is made from AR steel because it can take a beating and keep going. The same is true for AR steel body armor and rifle targets; they withstand far more damage than regular or mild steel ever could.

The number in AR500 and AR400 is an expression of Brinell units, which are units of hardness.  To determine a metal’s Brinell score, they take the metal and apply a weighted steel ball to it.  They then measure the depression left in the metal by the steel ball. The amount the metal bends under this weight determines the Brinell score. Based on this measurement, AR500 had less give than AR400.  When tested, the AR500 steel did not have nearly as much of a depression caused by the weighted ball as did the AR400 steel. (Go here to see the detailed formula for how Brinell Units are calculated).

AR500 Testudo Plate Carrier Multicam Gen 2 (Source).

Why AR500 is a Better Protective Material than AR400?

The hardness of the metal in your body armor plates is an important aspect to consider, but it is far from the only factor to take into account when choosing the right vest.  When your life is on the line, you have to know that your body armor is going to protect you. The AR500 has greater stopping power due to its superior hardness.

Properties of AR400 Plates

  • Far stronger than Common or Mild Steel, which only has a Brinell rating between 120 and 180.
  • Commonly used on construction, mining, and farming equipment for its toughness.
  • Cheaper than AR500.
  • 3/8th inch plate weighs approximately 10lbs per square foot.
  • Can stop standard handgun fire from .9mm, .40 caliber, and .45 caliber handguns.
  • Unable to withstand rifle fire at 100 yards.  The metal is too soft, causing it to pit under the pressure of the projectiles. 

Properties of AR500 Plates

  • Harder than AR400 steel on the Brinell Scale by 100 units.
  • Commonly used on construction, mining, and farming equipment for its toughness.
  • 3/8th inch plate weighs approximately 7lbs per square foot.
  • Stops all standard magnum and non-magnum handgun calibers at 12 yards.
  • Stops shotgun slugs at 50 yards.
  • Stops non-magnum rifle calibers at 100 yards.
  • Stops magnum rifle calibers at 200-300 yards.

Why Hardness is Such an Important Factor?

Our skin is a poor protector for our body when it comes in contact with something hard and fast like a bullet.  To protect our fragile bodies from projectiles like that, we need something much harder, and that is where body armor and armor plating comes in. The hardness of the steel plates has to outperform the hardness and speed of any projectile seeking to harm our bodies.  The bullet type, size, and velocity all factor into determining what armor is needed to effectively protect the wearer.  Not all armors are equal.  A projectile of sufficient size, traveling fast enough, can defeat a lesser armor.

NIJ (National Institute of Justice) Levels

The National Institute of Justice is the research, development, and evaluation agency under the United States Department of Justice.  The NIJ has developed a system of measuring the effectiveness of body armor based on ballistic performance. The NIJ measures body armor to see that bullets fired at it are not able to penetrate the vest and that there is no blunt force trauma caused to the wearer by the bullet.  The NIJ has strict criteria for all body armors that they certify.  They also assign a specific level to the armor to indicate what extent of attack it can withstand.

  • NIJ Level IIA: Designed to stop a .9mm Full Metal Jacket round at a speed of approximately 1,165 feet per second and a .40 S&W Full Metal Jacket at 1,065 feet per second.
  • NIJ Level II: Designed to stop a .9mm Full Metal Jacket round traveling at a speed of approximately 1,245 feet per second and a .357 Magnum Jacketed Soft Point round at approximately 1,430 feet per second.
  • NIJ Level IIIA: Designed to stop a .357 Sig Full Metal Jacket Flat Nose bullet traveling at a speed of approximately 1,470 feet per second and a .44 Magnum Semi Jacketed Hollow Point round at a speed of 1,430 feet per second.
  • NIJ Level III: Designed to stop 6 hits of a 7.62x51mm NATO Full Metal Jacket round at a speed of approximately 2780 feet per second.
  • NIJ Level IV: Designed to stop 1 hit of a 7.62MM armor-piercing round at a speed of 2880 feet per second.

AR400 armor plates usually have an NIJ rating of Level IIIA or lower.  AR500 armor plates are rated as NIJ Level III.  Currently, only ceramic plates are rated NIJ Level IV.

Other Aspects of Your Armor to Consider

AR500 armor is superior to AR400 armor in toughness, but what about ceramic armor?  Also, since the AR500 armor is so strong, what happens when a bullet strikes the armor and then the bullet fragments? These are questions that have to be answered when evaluating what armor is right for your protection.

Ceramic vs. Steel

There has long been a debate about which is better, ceramic armor or steel armor.  Both body armor types have their pros and cons.  Steel armor can take multiple hits better, but it is heavier.  Ceramic armor can protect against AR-15 rounds and is lighter, but it fails to stand up against multiple precise hits. 

Ultimately, the decision between steel and ceramic comes down to preference and expected need.  If cost is not a concern, then ceramic may be a better choice for a lighter armor, especially if you are concerned with protecting against AR-15 fire.

The Threat of Spalling and Fragmentation

When comparing body armor, you must always consider the danger of spalling and fragmentation.  Fragmentation is caused by the bullet fragmenting into shrapnel.  Spalling is when the armor itself has small pieces of shrapnel break away due to the impact of the bullet. Shrapnel from fragmentation or spalling can then ricochet off of the armor and lodge into the neck, face, or other vital body parts.  This is a grave danger that must be accounted for when choosing the proper protective materials.

Body Armor manufacturers are aware that round fragmentation and spalling pose a serious threat to their customers.  To combat this, they have developed coatings that they put on their steel plates.  The coating traps the bullet and armor fragments so that they are less likely to be a danger to the wearer. Armored Republic has a proprietary FragLock™ polyurea formula that they use as a coating on their armored plates to reduce spalling and fragmentation.  The coating is layered extra thick and given just the right balance of elasticity and durability so that it can effectively contain any possible shrapnel and thereby better protect the wearer. 

Spartan Armor Systems have taken their efforts to prevent spalling and fragmentation a step further than just a coating.  They do offer a full coating, but they also offer a specifically designed Spall Sleeve.  The armor fits into a sleeve made of layers of specific fiber, which helps to further reduce the dangers of spalling and fragmentation.

How Bullets Effect Ceramic & AR500 Body Armor

The Difference in Wearing the AR400 Plates vs. AR500 Plates

The AR500 plates have a superior hardness and more stopping power than the AR400 plates, but they also have a different feel when wearing them.  Overall, the AR500 armor will be lighter and more versatile than the AR400.

Getting the Right Size and Fit

As stated before, stopping power is not the only thing to consider when choosing your armor.  Another important aspect to take into consideration is how it fits, how it feels, and what mobility it offers you.  Your armor is a tool meant to protect you, but if you are not comfortable in it, then you will not wear it, and then it can not do its job. The AR400 armor has more weight to it, so if that heavier weight is something you are used to, then this might be the right feel for you.  

However, if you prefer lighter armor, then the AR500 is the way to go.  This is something you will have to try and get a feeling for yourself.  The armor is worthless if you do not wear it, so you have to pick the one that you are most comfortable in. Getting properly measured for your armor is also extremely important.  If your armor is too big, then it may shift or sit wrong, exposing vital parts of your body that should be protected.  If your armor is too tight and it can not move at all, then not only does it become restrictive, but it also can cause you more trauma when the armor is struck by a projectile.

The armor you choose also has to allow you to move in it.  AR500 armor is lighter and, if properly sized, can allow for more mobility.  If you are wearing armor to protect yourself, then you are going to be in some dynamic situations that require fast and fluid movement.  In these life or death situations, you do not want to be hampered by your armor.

AR500 armor is lighter and, if properly sized, can allow for more mobility (Source).

Swimmers Cut vs. Shooters/Standard Cut

Most armor plates come in one of two cuts or shapes.  The plates are shaped in either the Swimmers Cut or the Shooters Cut.  The Shooters Cut is also often called the Standard Cut.

Shooters/Standard Cut

  • Pro: This cut offers more coverage of your body, greatly reducing the chance of damage to one of your vital organs and dramatically increasing your survivability.
  • Con: This plate cut is heavier and offers less mobility in the shoulders.  Some wearers find it difficult to properly maneuver and return fire while wearing this type of plate.

Swimmers Cut

  • Pro:  This cut is lighter than the Standard/Shooters Cut, and it offers far more flexibility in the shoulders.  Wearers have said that it is easier to seat the butt of a rifle or shotgun in their shoulder while wearing a Swimmers Cut plate.
  • Con:  This plate cut offers less coverage to your upper chest and shoulders.  This opens up more points of vulnerability and increases your chance of injury.

The decision between these two cuts is one that the wearer has to make.  Either you sacrifice mobility in exchange for a greater area of protection with the Standard/Shooters Cut, or you give yourself a greater range of motion at the cost of increased vulnerability with the Swimmers Cut.

Expected Threat

Another important aspect to consider when choosing between AR400 armor and AR500 armor is what you expect to use that armor for.  Preparedness is a necessity, and knowing what types of threats you may face can help keep you alive, as well as help guide you in choosing the best armor for you and your situation.

There is a lot to take into account when trying to anticipate what threats you will need to mitigate.  Are you wearing this armor for daily personal protection, or is this part of your work uniform?  A police officer has different threats to consider than the average citizen.  Military personnel has drastically different threats to contend with than anyone else.

If you don’t mind a heavier armor and you are expecting to primarily protect yourself from handgun fire, then the AR400 will do the job for you.  If you are expecting to need to protect yourself from rifle rounds, then the AR400 will not be your ideal choice.  The AR500 is a better fit for protecting you from the threat of rifle fire.

Overt vs. Covert

Another question you have to answer is whether or not you are going to wear your armor overtly or covertly.  Wearing your armor overtly, on top of any other clothing or gear, directly shows your enemies where you are and are not vulnerable.  Wearing your armor overtly will also directly announce that you are armored and a potential threat.

Wearing your armor covertly, concealed beneath other clothing and gear, allows you to be protected without making it immediately obvious.  Covert wear of your armor is preferable if you are wearing armor for everyday protection as this way, you will not call attention to yourself.  You can covertly remain protected without drawing notice. AR400 armor, being heavier and bulkier than AR500 armor, lends itself to overt wear.  AR500 armor, being lighter and more versatile, is optimal for covert wear.

Comparing Vests

Here we will compare some of the more popular Armor Vests on the market so you can get a side-by-side breakdown of their attributes.  These are all AR500 steel armor as AR500 steel has quickly become the go-to protective material for modern steel armor plates.

NameRTS Tactical Body Armor Level III Steel Active Shooter Kit Armored Republic’s Testudo Gen 2.0 Plate CarrierSPARTAN™ OMEGA™ AR500 BODY ARMOR ENTRY LEVEL PACKAGE
Plate Type and SizeAR500 10”x12” SAPI Cut Single Curve armor plateAR500 10″x12″ Standard Cut Flat Armor Plate10”x12” Spartan™ Omega™ AR500 Body Armor Plates, Single Curve
NIJ LevelNIJ Level III – protects against High-Velocity Rifle Ballistics NIJ Level III – protects against High-Velocity Rifle Ballistics NIJ Level III – protects against High-Velocity Rifle Ballistics 
ExtrasNIJ Level III AR500 6”x8” Side Insert armor plates, Anti-Spall self-sealing polyurea coatingCan be upgraded to an 11”x14” armor plate, FragLock Coating for Fragmentation, and Spall protectionCan be upgraded to an 11”x14” armor plate, ENCAPSULOC™ anti-spall coating.

Remember, You are Not Superman

Regardless of which armor you choose, even if you get the superior AR500 steel, it will not make you Superman.  Body armor, no matter how strong or what it is made of, does not make you invulnerable.  It is misleading to call body armor a “bulletproof vest,” as body armor does not make you bulletproof, only bullet resistant. It is still possible for the best armor to fail.

Because of this, it is important to carefully choose the best armor for you.  Stack the deck in your favor as much as possible.  Even though the best armor will not make you invincible, any armor is better than none at all, and the right armor can save your life even in the worst of times.

AR500 Armor Plates are the Better Protective Material

There is quite a lot to consider when choosing what body armor is right for you.  All of these choices have to be weighed carefully since your life can potentially be on the line.  One thing you can be sure of, though, is that AR500 armor plates will protect you better than AR400 plates.  With that knowledge in mind, you can start researching all the other aspects of your body armor.


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Kevin was born and raised in Texas and loves all things tactical. His hobbies include shooting, hunting, rock climbing, and hiking with his dog Jax.

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