The concept of “bulletproof” is as conflated as the concept of “inflammable”, yet both are used quite often in our descriptions of materials. The truth is, nothing is truly bulletproof, in the same sense that nothing is truly inflammable; if you get something hot enough, it will burn, and if you launch a projectile fast enough, it will punch through anything. They are concepts that are subtextually understood to be relative, such that describing something as bulletproof means to say it is reasonably bulletproof. Though somewhat pedantic, this annecdote is an important predicate for our topic today.
I recently saw John Wick: Chapter 4, and have been thinking about one of the series’ signature elements: the bulletproof suits. Throughout the films, John wears specialized kevlar suits that allow him to essentially eat bullets, something the series has wholeheartedly bought into in the latest film, with John and other assasins often comically tucking their lapels over their heads as they fight.
Interestingly, the concept of “ballistic chic” is nothing new. Here’s a morbid article published in The New York Times from 1981:
As with current pundits suggesting “bulletproof backpacks” as a response to the school shooting epidemic, here we see a vintage example of addressing the effects of violence, and not their causes.
The question at hand is simple: Do bulletproof suits—as used in the John Wick franchise—exist? If not, are they plausible? I hope you’re not scared of math.
The Nitty-gritty
For the first time since graduating, let’s put my physics degree to use.
First off, we need to pick our poison. Wick, although no stranger to a diaspora of weaponry, is often toting a pistol as his firearm of choice. For the sake of this experiment, we’ll stick to 9mm parabellum, as it is one of the most common pistol cartridges around, and one Wick explicitly uses in the latest film.
Our goal is to do a little bit of research and calculation on 9mm parabellum, as well kevlar in order to determine if a bulletproof suit akin to Wick’s is capable of withstanding bullets, as well as keeping its wearer alive and kicking. In order to do this, we need some initial statistics, including the velocity of 9mm parabellum, and its weight.
Using this website, I was able to calculate the muzzle velocity of 9mm parabellum, as well as its velocity after 1 foot. Why one foot you ask? Because most of Wick’s exchanges occur in extreme close quarters combat (CQB), with rounds being exchanged at point blank range.
Here is our data set:
We can glean from this that the velocity of the bullet after it has travelled one foot will be around
Now, we need to look into kevlar and the dimensions of our theoretical suit. We’ll be generous and measure the thickness of the suit from the lapel, using one of my own suits as reference.
From this incredibly precise measurement, we get a thickness of ~ 1cm. We will assume that we want the bullet to only penetrate half this thickness (if it went the whole way, then it wouldn’t be very effective bulletproof suit, would it?), giving us a penetration distance of 0.5cm=0.005m
In order to calculate the force required to stop the bullet, we need an acceleration.
For simplification, we’ll just say the bullet takes 1ms to travel 0.5cm into the fabric. Our initial velocity will be the velocity after 1 foot of travel, which we found previously to be 380.4 m/s. The final velocity will be 0m/s, as the bullet will be at rest.
Now that we have our accleration (deceleration, rather), we can go to our trusty friend Newton.
The weight of a 9mm parabellum bullet—according to the ballistics website I used—is around 115 grains, which is about 7.45 grams, or 0.00745 kg. Plugging and chugging, we get
According to our calculations, the suit lapel would need to be able to exert/absorb 2.8 thousand newtons of force in order to stop the bullet halfway through the material. For reference, the strongest bone in the body—the femur—takes about 4000 newtons to snap.
However, it’s important to note that this force isn’t typically applied as a point source. In fact, there are many ways a bullet can possibly impact. In the case of a bullet penetrating the human body—which is full of incongruent assemblages of muscle, ligaments, and bone—the bullet will likely fragment. When unable to penetrate, the bullet will crumble, flattening out like a pancake.
This dispersion of force is essential to how kevlar vests work in the first place. By combining layers of treated kevlar, the force is able to be displaced in a myriad of directions and capacities, the kevlar essentially stretching in a transfer of kinetic energy. It’s ultimately kevlar’s ability to gradually dampen the force of a bullet, not stop it outright like a brick wall, that protects its wearer. That said, 2.8kN is one hell of a punch, and to have a material that thin be able to be that sturdy would probably entail a fair bit of weight, far heavier than a conventional suit jacket.
I found this scientific article, which examined the penetration of various rounds and combinations of layers of kevlar. The study concluded that for pistol rounds, 21 layers of kevlar are recommended to adequately stop the bullet. From a brief search, 21 layers of kevlar is about 0.7” of material, which is over three times the thickness of our suit lapel measurement.
So, does something like the John Wick suit exist? As it turns out, Youtube channel Hacksmith Industries spent a year developing their attempt at replicating a John wick suit. They were able to fabricate a suit that could withstand pistol rounds.
However, this was accomplished using both a suit and a vest beneath it. Further, it was shot from a few meters, with no real way to measure the impact the bullets would have on a live body even though they did not penetrate.
This brings us back to our cursory discussion on semantics. The suit that Hacksaw Industries made is “bulletproof” in the sense that bullets could not pass through it, but as we’ve expounded on, the effects of a bullet go beyond its ability to physically enter the body.
All this is to say getting shot with a bulletproof vest on hurts, and is still potentially life threatening, even if the bullet doesn’t penetrate your body. Could the John Wick suit exist? Maybe, but there’s no way in hell someone could take the amount of bullets he takes and stay standing.