The Basics of Firearms and Body Armor

​In our modern society, it is important to learn how to protect ourselves. No matter your stance on the subject, education on the topic will only improve your ability to make informed decisions both in your safety and the safety of friends and family. Body armor is a self defense tool, similar to a knife, firearm, taser, baton, or something else. While body armor is effective on it's own, it is important to have both sides of the equation. Just as a car has a brake and an accelerator, and both perform their functions separately, they function better together. However, to understand how body armor works, we must first understand what it is we are protecting against. Firearms.
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What is a firearm?
A firearm is a tool that forces a projectile down a barrel by controlled explosion (explosions are events of rapidly expanding and high-pressured gas). There are two types of explosions, conflagration (supersonic) and deflagration (subsonic). Modern firearms almost always work off cartridges that deflagrate, and other methods are outside of the scope of this article.

What is a cartridge?
While it can be called many things such as a round, bullet, or cartridge, this article will refer to them as a cartridge. A cartridge is a culmination of a projectile (what actually leaves the gun), casing (holds the other components), powder (the propellent that becomes the gas and by extension the driving force of the projectile) , and primer (a smaller more sensitive explosive designed to begin the deflagrating explosion) as shown below:

​Projectile: what leaves the gun
Casing: Holds the other components
Powder: The propellent that becomes the gas and by extension the driving force of the projectile)
Primer: A smaller more sensitive explosive designed to begin the deflagrating explosion)

When a firearm is fired, a pin or striker hits the primer which explodes, and ignites the powder. The powder begins to deflagrate and rapidly converts into a gas. This sudden change into a less compact state of matter forces the projectile out of the casing. There are many more intricacies to this process such as atmospheric pressure, temperature, powder type, projectile weight, how far the bullet is seated, chamber pressure, pressure inside the casing, etc. but once again, these will be covered in future articles. One thing to note is that while there are explosions in the firearm they are noting to be afraid of and as long as you follow the manufacturer specification on the pressure of your ammo, you will be safe save for extremely catastrophic design failures.

Once the cartridge has been fired, the bullet will travel down a barrel. A barrel is a straight, usually metal tube. When it is rifled it puts spin on the bullet which helps it be more accurate, similar to the spin on a football. One notable instance where this is usually absent is in shotguns which are called smoothbore firearms.
Once a projectile leaves a firearm, it always hits something whether it is the ground or a target. It is important to remember projectiles do not just disappear! Modern weapons make it easy on us as they are all relatively accurate and shoot in a straight line (but not a straight trajectory) from where the barrel is pointing. Always ensure you know what is in front of your barrel and never put your finger on the trigger unless you intend to shoot.
Now we get into the more difficult part of determining how a projectile will interact with the target it strikes. There are several things to consider, and many times they are best to compare to each other, not in a vacuum.
The energy a bullet has is measured by the formula

​E is the total energy in foot pounds
M is the mass of the projectile in grains (there are 7,000 grains in 1 pound)
V is the velocity of the projectile in feet per second
*the divisor converts the equation into foot pounds 

For example, a 180 grain 7.62x51 traveling at 2,700 feet per second would produce about 2913 ft/lbs of force, and a 200 grain 7.62x51 traveling at 2,700 feet per second would produce about 3236 ft/lbs of force. This is a convenient way to compare these two loads, however velocity and mass are usually inversely proportional although not directly so. Most of us also cannot guess what 3,000 ft/lbs of force applied over 7.62 mm would feel like or do, so again it is best to use for comparison.
A bullet with greater energy, all other things being equal, will do more damage to what it strikes. Another formula we can use is to find something called sectional density, or how dense it is for its size

SD is the sectional density
M is the mass in grains
D is the diameter of the projectile

For example, those same 7.62x51 loads would come out to an SD of .271 for the 180-grain load, and an SD of .301 for the 200-grain. This shows that if all other things are kept equal, the 200-grain bullet would penetrate better than the 180-grain. You can also see using the previous equation that it produces over 300 ft/lbs more of force than the 180-grain.
 
In the modern era, there are a few methods of operation firearms generally follow. Think of it as the difference between manual and automatic cars. They work differently but they achieve the same general purpose.

Bolt action: After every round, the user must cycle a bolt manually, loading the next round from the magazine (covered below).
Semi-automatic: The firearm cycles itself after each round, and fires one round per operation of the trigger. This is it. It is not a weapon of mass destruction or pure evil.
Automatic: The firearm cycles itself after each round and fires more than one round per operation of the trigger. Note that this could mean two, or three, it does not have to fire until your magazine is empty.
Pump action: The user must manually cycle the action after each round, usually found on shotguns but it has recently become more popular in rifles again.
Single shot: The user must load a round into the weapon after each shot.
Note: There are more methods like rotary and lever action, but they are not nearly as commonly encountered.

Two more features modern firearms usually have are a magazine and a muzzle device. Magazines are places where cartridges are held. The two kinds are external and internal. External magazines are much more popular as they can be extended, quickly swapped, and if they fail, they are cheaper to replace. These allow users to reload quicker and to quickly swap between types of ammunition. Internal magazines are held inside the gun and are slower to reload as you must load each individual round, although I suppose you cannot lose internal magazines. Muzzle devices modify the end of a barrel to receive some desired effect. They usually do this by manipulating the gas that exits the barrel. Suppressors catch and slow the gas to reduce noise, muzzle brakes redirect it to reduce recoil, and flash hiders disperse the gas to reduce signature.
Now that we know how the firearms and projectiles work, it is easy to explain how body armor works. Soft armor works by spreading out the force over a larger area, reducing the bullets sectional density. This reduces or stops the penetration of the bullet and saves the wearer from having holes poked in vital areas. One common misconception is that it will not hurt, but just like the projectile, the kinetic energy does not disappear! It is still transferred into the armor, but it is spread out over a larger area, reducing the damage to the end user. Hard body armor works by being harder than the bullet, deflecting or shattering the projectile. It also does disperse the force over a wider area, but it does not work because of this principle. Soft armor will only realistically stop handgun rounds, and hard armor will stop both handgun and rifle rounds. There are exceptions such as ceramics, and hybrids but those will be covered in another post.
Answering some common questions:
Here at Wave Industries, we have received some questions repeatedly and I would like to take a crack at answering two of them

Does body armor fail?
Yes. Body does fail, and it relies on myriad of factors. For example, how was the armor stored? Has it been shot or dropped? Has it been exposed to harmful chemicals? Has it been kept in the trunk of a car in Death Valley? Did the shooter use rounds designed to penetrate armor? Did the shooter use a wildcat round that has a very specific ballistic profile (6.5x25 CBJ I’m looking at you and your beautiful designs)? Was the armor rated to stop the cartridge it encountered? There are far too many variables to account for when manufacturing body armor.
To reduce the likelihood of this occurring, the user can do several things.

1. Decide what you are likely to encounter and be honest. When picking your body armor, you must decide between hard and soft armor, what format you would like it in, and what weight you are comfortable with. If you decide on Level III+ hard plates and a vest, to achieve protection you must be okay with wearing 10 or more pounds in a large bulky vest each day. If you are likely to encounter rifle wielding enemies, this makes sense. However, you are much more likely (22.23 times as likely, see below) to encounter handguns. If your armor is lighter, flexible and more comfortable you are less likely to decide “I just don’t need it today”. Only you know your situation and it is up to you to figure it out. You may also consider bag inserts as they can weigh as little as 8 ounces and you may not even notice a difference daily.

2. Take care of your armor. Body armor is an investment in your protection, and it can save your life. It is important to take care of it in return by following your manufacturers instructions and treating it as gently as possible. It will not break if you sneeze on it but try to avoid dropping it from 20 feet in the air. Do not bend your armor like a piece of paper either, it can weaken along the fold lines.

3. Pick armor that stops what you carry. If you carry a firearm or taser, ensure that if you should be unlucky and have it used against you, you are protected. For example, if you carry a 9mm handgun, ensure your armor stops 9mm. Likewise if you carry a 5.56x45 all day, ensure you have level III plates that would stop your cartridge. And if you are that guy that happens to carry a .338 Lapua Magnum, or .416 Barret make sure you have Boron Carbide and a whole lot of luck if it is ever used against you.

4. Do not give up. Body armor is a complicated topic and unfortunately the answer is almost always “it depends”. One thing you can be reassured of though is that your chances of being safe are almost always better with it and are never hindered by having it. Lucky this industry has many knowledgeable professionals and you should never hesitate to reach out if you have a question.
 
Why is there so much legislation targeted at rifles?
This will be a long one. The answer is, well, we don’t know. It could be due to common misconceptions. Ask yourself, what type of firearm is most often used in mass shootings? Did you come up with an answer? Was it “assault rifles”? If so, you would be incorrect.

​For every rifle used, there are 2.56 handguns used. Handguns also lend themselves better to concealment. It takes a large person to conceal a weapon that is 28-40 inches long, especially given that firearms do not bend (if your firearm bent, you have used it wrong) and it is unlikely that it would be overlooked. Despite media coverage, mass shootings actually cover a very small portion of shooting crimes in the United States, and a disproportionately high number of rifles are used. As you can see below, in general crime you are 5.1 times more likely to be killed by cutting instruments, 2.2 times as likely to be killed by fists or feet, and 1.49 times as likely to be killed by blunt objects. That is totally disregarding the fact that you are a willy whooping 22.23 times as likely to be killed by a handgun as a rifle. 

​The last factor I can think of is fear. One name most people recognize is "AR-15". Many people take AR-15 to mean the 15th assault rifle, or other such silliness. AR stands for Armalite, the original company to design this family of weapons, such as the AR-7, 10, 15, and 18. These platforms actually originated as early PDW's or personal defense weapons for aircraft survival crews who needed something light to defend themselves with. Modern day "AR's" are sporting rifles designed for "plinking" which is shooting holes in paper, or varmint hunting. 

Assault rifles are select fire (read automatic) weapons and have been illegal to manufacture sine 1986 for civilian use, and weapons manufactured before then are subject to the NFA to be possessed. Only military and police officers can have the modern ones. Fortunately, since 1934, there have only been “two homicides committed with legally owned automatic weapons. One was a murder committed by a law enforcement officer”. It is interesting that not one legal select fire weapon has been used in a mass shooting, yet this is what legislation targets, and the words the media chooses.
 
Sources:
1. https://guncite.com/gun_control_gcfullau.html
2. FBI. "Number of Murder Victims in The United States in 2018, by Weapon." Statista, Statista Inc.
3. Mother Jones. "Weapon types used in mass shootings in the United States between1982 and August 2018" Statista, Statista Inc.