Ballistics: Three Myths That Can Kill You

Ballistics is the dark mysterious study of bullets in flight.  No subject garners as much anecdotal b.s.  The fact is that much of the data is fairly straight forward and is governed by simple physics.  You guys remember physics class right?  It was taught by the troll looking guy with coke bottle glasses who always smelled like canned soup.

This article will review scientific data for calibers most often used in concealed carry and home defense.  I will show you what these rounds will actually do when they hit cars, walls, and human flesh.  After reading the article, you will have a good idea of what home defense round you should use, what you should and should not shoot, and hopefully, we will have dispelled myths that could put you or your loved ones in danger. 

Ballistics Overview

Ballistics is the study and science of projectile, firearms, and their effects.  For the purposes of this article, we will be investigating scientific data relating to self defense calibers in order to better understand what they do to humans.  To do that, we will be looking at ballistic gel experiments as well as bullet penetration tests.

Terminal Ballistics and Wounding

Terminal ballistics is defined as the effects of a bullet at the termination of its flight.  Specifically, we will be looking at bullet wounding in humans.  There are three components of bullet wounding: bullet channel, permanent cavity, and temporary cavity.

In fact, bullet wounding can be defined as damage produced by penetrating bullets which depends on the impact energy that is delivered to the tissues, the rate at which this occurs, and the local response of the tissue subjected to it’s effects.

Gun shot wounds are considered a special form of blunt trauma. They do not consist simply in plain tissue penetration, since they involve crushing due to overpressure in front of the projectile, and also indirect damage from temporary cavity formation in its wake region, called cavitation.

Myth #1

This brings us to our first myth that bullet efficacy depends on the size of the bullet.  This is categorically false.  As was mentioned above, there are three mechanisms of injury and the size of the bullet only impacts one aspect of the triad.  Sure, a bigger diameter bullet will cause a bigger permanent wound channel, but it will not necessarily have any  greater cavitational effect, which causes the vast majority of injury.  Check this video out. Even the maker of the video is surprised how little bullet size matters.

From this video we can see that the permanent cavity created by the 9mm round was much bigger than that of the 45 acp. So much for that knock down power huh?

Now that we have seen what relatively low powered handgun bullets can do to ballistics gel lets look at a 5.56mm in gel.

You can see that the bullet does not travel in a linear fashion through the gel.  As it encounters more and more resistance it begins to travel side ways or yaw.  This eventually results in bullet precession, which is the bullet traveling forward, leading with it’s rear.

Yaw and precession account for bigger permanent wound cavity creation than in hand gun rounds, but as you can see, that is only the tip of the iceberg.  The cavity created behind the bullet is much larger than the permanent cavity.  This review of bullet wounding sums up this point nicely

“As the projectile is moving forward, tissue detaches from the projectile-tissue interface, as a result of boundary flow separation, and is subsequently accelerated radially, the same way as a speedboat displaces water, while the momentum imparted to tissue particles results in the formation of a vacuum. The underlying process called cavitation becomes clinically important at impact velocities exceeding 600 m/s, thus considered the most important feature in wound ballistics of high-velocity projectiles”

This bring us to our next myth concerning the infamous 7.62 x 39mm vs. 5.56mm debate.

If you like this kind of article, then put your email in on the right, and join the 1563 members of the Tier Three Team.  If you don’t I’ll hire a hobo to give you awkward hugs

Myth #2

Most shooters would agree that 7.62 x 39mm has more knock down power.  In fact many Marines I served with told me this numerous times ; however, this is not an accurate statement.  Rounds fired from an AK-47 do have more muzzle energy but that is irrelevant to actual wounding.

In fact, it is only the energy deposited to the tissues that is transformed to work resulting in tissue disruption that truly matters.  And 5.56mm rounds do this much better.

According to this study, the small-caliber bullets of the M16 and Kalashnikov AK-74, 5.56mm and 5.45mm respectively, yaw and tumble significantly earlier than the twice heavier bullet used by the ubiquitous AK-47 rifle and they create large wounds early in their path.  In effect,the faster and smaller bullet creates a larger wound cavity and a larger temporary cavity due to its higher velocity as it enters human tissue.

I know some of you are having a hard time believing this, you are probably saying,”but what about all the stories where someone is shot with an m16 numerous times with little effect?”

Unfortunately, you can’t shoot the same person, at the same time, in the same way with two different rounds to see which works the best.  I would imagine that had you shot that person with an AK-47, the effect would have been the same. The only way bigger rounds work better than smaller rounds is if they maintain the same velocity as their smaller cousins.

Unless you shoot them in the melon, you are only disrupting their tissues to the point where vital biological systems no longer function and that takes time. There is no magic round that can escape the laws of physics, except maybe that JFK one, oh, and those bullets Angelina shot in Wanted.

Penetration and Cover

We have covered terminal ballistics in humans, but what about the ballistic effects on other materials?  In this section we will discuss the ballistic effects on the two most important types of objects for the tactical shooter, cars and homes.  Why these two you ask?  Simply put you spend most of the time in and around these two types of objects.

Cars

First lets look at Hollywood gunfight around cars.  This is from the movie John Wick, which is totally badass, but unfortunately not realistic.

Any rifle round, and the vast majority of hand gun rounds will not be impeded by sheet metal, which account for the bulk of any vehicle.  Only an engine block, axles, and possibly the wheels will reliably stop or deflect rounds.  Look closely at the video and you will see the bad guy’s shooting at the SUV as Wick moves behind the bullet path at the rear quarter panel.  He would be dead, end of movie, no sequel.

Now we need to discuss hugging too close to the vehicle for cover.  Kyle Lamb, formerly Army Delta, shows this concept quite well.

Bullets can skip off of sheet metal. Don’t suck up to the car for cover, and if you are close, for God’s sakes don’t stand in the door.

Homes

The next area where the majority of us spend our time is in our homes.  It’s where we keep our firearms and it is an area where we have the responsibility to defend.  There are a huge number of opinions on how to defend your home and what weapon is best.  In this section, you will see that there really is no best weapon, only weapons that work better in certain situations. The three rounds we will consider are the 9mm, 5.56mm, and 12 gauge.  Yes there are others, but we will cover the most popular weapon calibers.

Round Selection and Home Defense

Before we go any further, we need to define what our goals are when we say home defense.  The first priority is to keep everyone in your household alive.  You need to use a weapon that will produce agonal (life threatening) wounding relatively quickly if you are forced to use it. You must use a weapon that is least likely to create danger for your family or your neighborhood.  It doesn’t matter if you drill some criminal right in the chest if your round blows through him and into your neighbor’s bedroom.

Now that we have defined goals, we can go about selecting the weapon system that will allow us to accomplish them.  Using our priorities we must first select a weapon that will help keep you and your family alive by producing agonal wounding in your attacker.

What about a 12 gauge, check, 5.56mm, check, and 9mm, probably not as well.  A 9mm is a great round to carry, but if you are talking home defense it is probably not ideal compared to the others.  I can hear some of you now yelling about over penetration with the rifle round.  Well I’m glad you mentioned that.  You folks have fallen for our third myth.

Myth #3

Most folks assume that handgun rounds will not penetrate structures of a house as deeply as higher energy long guns.  Well that is simply false.  Check this video out.  To see all three at once go to 6:40.

Still not convinced.  The Marine Corps Military Operations in Urban Terrain (MOUT) manual further confirms the penetration effects of rifles.

“(1)For the 5.56-mm round, maximum penetration occurs at 200 meters. At ranges of less than 25 meters, penetration is greatly reduced. At 10 meters, penetration by the M16 round is poor as a result of the tremendous stress placed on this high-speed round, which causes it to yaw upon striking a target. Stress causes the projectile to break up, and the resulting fragments are often too small to penetrate.”

In effect, the only round that will not penetrate multiple walls is bird shot out of a shotgun.  Check this video out regarding various 12 gauge loads.

Now we know that all three of our choices are likely to penetrate multiple walls, what about other structures in the home such as brick or stucco? This study, sponsored by Interpol, shows penetration characteristics for multiple calibers on common exterior constructions.  The bottom line is that only brick or concrete provide excellent protection with vinyl and stucco providing little to no protection.  So where does this leave us in terms of home defense?

Choosing a System

In order to best choose a system, you need to take a hard look at the layout of your home.  If you live in an apartment or town home a shotgun with something like #4 buck shot is ideal.  You can still shoot through a wall if needs be, but you are not likely to kill your neighbors.  The shot pattern is also going to be very small at CQB distances, and it will have great effects on any intruders. Check this video out, covering it’s benefits.

If you have a single family home and live in a neighborhood you have a few more options depending on your location.  You might choose a 5.56 caliber weapon for its superior ability to produce agonal wounding.  However, you must be very aware what areas you may not shoot for fear of hitting loved ones or neighbors.  If that sounds like too much for you in the heat of the moment, pick the shotgun.

I would recommend handguns as a last choice.  They are the hardest type of weapon to shoot, they produce just as much penetration through interior walls as rifles, and they take the longest to kill.  You will need to be very aware of over penetration effects.

Lastly you need to consider you interior layout and family type.  If you have a large family in different areas of the house then over penetration is a very real danger.  For the vast majority of folks, a 12 gauge with with an extended mag full of buckshot, and a light will be the ideal setup.

Review

We’ve covered a lot of information. So, let’s do a quick recap.  First bullets cause injury by creating a permanent bullet channel, a permanent wound cavity, and a temporary wound cavity.  The size of the bullet only creates a slightly larger channel it does not cause any increase in wound cavitation.

Next, we learned that bullet yaw and precession are greater in 5.56mm bullets and, as a result, create much more injury in humans than AK-47 rounds.  Lastly, we learned that pistol, shotgun, and rifle rounds penetrate multiple walls to a near equal extent.

In choosing your home defense weapon, you need to consider very carefully the layout of your home and neighborhood to best keep you and your family safe.  As always, the best home defense weapon is the one you have and can effectively use.