why are body armor vests so small?

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Always seems like there are big parts of the chest not covered by the Kevlar. I get that there maybe aren’t organs up by your shoulders, but, seems like it makes it easier for bullets to come in from the side. Why not just have more coverage?

In: Engineering

Mobility, remember the times these things are used are often combat, you don’t want anything impeding someone’s ability to use a gun without messing up their aim and muscle memory

Cause you are essentially protecting your vitals. Soft body armor like kevlar vest worn to protect you from pistol caliber armor typically covers a larger portion of your body. Hard armor like ceramic plates for rifles are smaller and only cover the areas where being hit is going to result in rapid death/incapacitation. And covers less for weight and to allow more maneuverability

Because it’s meant to be worn for hours at a time and a large piece of body armor is heavy and hard to move in

There are different types of body armor with different levels of protection. For example flac vests do offer more protection to the sides, shoulders, neck and groind. And these were issued to infantry in early Vietnam war deployments. The problem with this type of vest is that in order to protect these areas they restrict the mobility of the wearer, which can be more deadly as they are unable to observe dangers and respond to them in a good way. For example body armor which makes it uncomfortable to fight kneeling down or laying down will cause the soldier to remain standing when fighting exposing their body even more. Thus the body armor increases the risk of harm rather then decreasing it. So even during the Vietnam war soldiers modified their flac vests to remove these restrictions. Opening up their collars and removing sholder protection.

There are lots of body armor that cover the whole chest area with kevlar. The former US military [ Interceptor_Body_Armor](https://en.wikipedia.org/wiki/Interceptor_Body_Armor) is an example of this.

It is modular so you can add arm, neck, leg, and another part to it as required. You can see it cover almost all of the body on [this mannequin](https://upload.wikimedia.org/wikipedia/commons/3/38/USMC_Turret_Gunner_mannequin.JPG)

It has ballistic plates that can protect the front, back, and sides of the torso,

The problem with body armor is that is heavy and not that conformable to wear. It also do not let air or moisture through so you get warm in it and sweat can’t get out.

Kevlar that is flexible can handle bullets from pistols and some fragmentation for explosions but not bullets from intermediate or full caliber rifles. You need stiff ballistic plates for those.

The result is that the level of body armor is a compromise between risk, protection versus weight, comfortableness.

Just protecting the front and back of the chest that can include ballistic plates gives you quite good protection but you can keep the weight down and make them quite comfortable so it is good enough for many situations like the police.

For military usage adding a kevlar that covers more primary is protection against fragmentation from artillery, hand grandad etc that can hit you from any direction. For non-military usage, fragmentation protection is not that relevant because it is not something that is common.

Modern military body armor is historically almost exclusive protection against fragmentation not bullets. Bullets in a military conflict are primary rifle or intermediate caliber that is hard to protect from. Artillery has also been the primary killer in large wars at least since WWI. From WWII you find numbers of 75% of all casualties are from artillery, So this is what military helmets and body armor is primary for.

Heavier body armor that can stop rifle and intermediate caliber bullets have primarily been in military usage for the last two decades in “War on terror” that has been asymmetric warfare ie standing armies vs insurgency or resistance movement militias. The usage of artillery against the standing armies has decrease and small arms or improvised explosives have increased.

Body armory has changed because the primary threat has changed.

The best way to survive a gunshot is to not get hit. Covering more of someone reduces their manoeuvrability, meaning they can move as quickly so they’re an easier target. It’s a balancing act between covering their vital organs so that any hits are more likely to be survivable, and allowing them to get out of the situation.

Like many things in engineering design, it’s a compromise. Body armour is heavy and rigid. Wearing it makes doing your job more difficult. The compromise is to cover only the vital organs.

It is a trade off between mobility, endurance and protection.

Too much weight: you can’t last long before exhaustion

Too much coverage: you can’t move because the armor blocks you

Too light armor: you die IF you are hit.

For example: specialists that go disarm bombs don’t need mobility or endurance, and they are covered with massive full body armor.

Opposite: a scout, he need to carry food and water for days. Armor can be the last priority

Because there are factors outside of pure defensive protection, which are also high priority. Weight load, mobility, ease of use, etc. It’s all a trade off of one vs others.

If I have a full upper torso protection, with plates on all sides, but I can’t run/duck/crouch, I’m just going to get shot/blown up when I take fire.

In the US military, we don’t even typically use a lot of the parts of the armor we have. We typically prefer the lighter weight and easier movement vs a little more side protection, crotch guard etc.

They’re really heavy. A buddy of mine who did a couple tours always explained it to me as you can tell how much shit people have seen by how much equipment they take with them. A newbie soldier is going to go out in full armor and be kitted out. A seasoned soldier is going to wear as little armor as possible and only take what they actually need because it’s heavy and hard to move carrying all that crap.

The whole point of body armor is to make someone relatively safe from dying and restrict their movement as little as possible. So, yea you could make someone way safer by adding more protection elsewhere on the body, but then both the weight and the shape start to restrict movement to a point that isn’t acceptable for a lot of people. Basically it’s better to take a shot to the arm while running away than to be weighed down by your vest so you can’t run.

All armour is a trade off.

Generally the stronger and more protective the armour is, the more constrictive and heavy it will be. The more constrictive and heavy, the less you can move and the more trouble you will have responding.

So the aim is to find a good balance that protects the vital organs (clustered in your chest and abdomen), while leaving your other limbs free. It is also notable that while they can often be life altering, bullets to the arms, shoulders and legs are much less likely to be fatal – again this is just the designers deciding what needs prioritised and what can be left out to gain back other advantages.

So the reason you usually see the best shape with cutouts at each shoulder is because that shape covers the important vitals, and benefit of having your shoulders fully mobile outweighs the risk of getting shot (or that shot being fatal).