Posted On September 27, 2013 by Print This Post

Buildings and Automobiles and Guns, Oh My!: A Brief Discussion of Terminal Ballistics

ADAM FIRESTONE is back! When I attended his weapons workshop last year, his discussion on terminal ballistics held us all spellbound. Since then, I can’t watch a movie or TV show without thinking about Adam’s comments. Read on to avoid making these common mistakes in your action scenes!

I don’t go to the movies very often. There are a number of reasons for this.

First, the thought of paying $15.00 to sit among people who are physiologically unable to silence their cell phones, refrain from texting or stop talking about the latest episodes of any number of reality television shows results in a reaction ranging somewhere between dread, loathing and the slowly mounting terror that comes with realizing that the sushi one had for lunch wasn’t quite…right.

Next, I spend a lot of time on the inside of airborne aluminum tubes. I’m just as much a bibliophile as the next jet-setting hoplologist, but sometime after the second hour of a nineteen hour flight that took off at 11:15 PM, the words on my Kindle’s screen start to shimmer and swim, the infant two rows back starts to bawl and there are many hours until the next meal service. At that point I retreat into the world of cinema…And all that, boys and girls, was a long way of saying that I much prefer to see NEW movies while I’m a captive audience than ones I’ve seen a number of times.

Finally (and this really tears it) I’m unable to suspend disbelief when it comes to portrayals of firearms and their use. I’m the unfortunate soul for whom the movie is ruined when the 41st round comes out of a fifteen round Glock magazine. Or, worse, when the Cadillac is blown sky high when the protagonist shoots it once with his hunting rifle. Moreover, the disappointment increases – verging in fact, on a sense of betrayal – when a book is involved. There’s a greater sense of involvement that comes with imagining the scene than when we merely consume someone else’s vision.

Misery, however, loves company. And so, for the rest of this piece, we’ll be discussing the realities of how things react to being shot. You know, so YOU can go to the movies and mutter disgustedly under your breath “THAT’S not the way it works!”

Vrooom! Screech! and Bang Bang Bang

The scene is a familiar one. The police cruiser arrives at the scene. Officers fling open the doors, leap out and take shelter behind opened doors. It’s so iconic and so dramatic that it’s practically the action scene archetype. And it’s so very wrong. But let me back up a bit and take this step by step.

1. Handgun vs. Windshield Glass

Good guy on foot, pistol in hand. Bad guy is driving a car, at a high rate of speed, intent on squashing the good guy like a bug. Good guy, unperturbed, takes careful aim at the bad guy’s noggin, and BANG – the bullet goes through the windshield like it’s not there and the bad guy is toast. Unfortunately, physics gets in the way, and it doesn’t quite happen like that. Windshield glass is hard. Really hard. So hard, in fact that it can be used to stop bullets. And even if it doesn’t stop a projectile, a windshield can significantly alter its flight path. Take a look at Figure 1, below:

Figure 1, Windshield Effect on Handgun Bullet

Figure 1, Windshield Effect on Handgun Bullet

There are a couple of factors that are important to remember. One, handgun bullets move at relatively low velocities (between 900 and 1,300 feet per second). Two, they tend to be blunt or flat nosed. Also, windshields are sloped. When a handgun bullet strikes a windshield, unless it has been fired from above the car, it does not strike squarely. Instead, the lower portion of the bullet’s nose strikes first, and slows down first. At the same time, the upper part of the bullet is still moving at speed. As a result, the bullet pivots as it penetrates the windshield, rotating toward an angle where it is perpendicular to the windshield. The flight path also changes, and the bullet, instead of moving along the original line of sight, flies in a downward direction. Practically speaking, this means that the good guy’s headshot is very likely to wind up striking the bad guy in the shoulder or chest.

2. Rifle vs. Windshield Glass

The behavior of modern rifle bullets differs from that of handgun bullets. For one thing, they move MUCH faster – typically between 2,000 and 3,000 feet per second at the muzzle. This means that while in flight, they are much more energetic than handgun bullets. For example, a typical 9mm Parabellum handgun bullet has between 350 and 400 foot-pounds of energy at the muzzle. In contrast, a .308 Winchester bullet may pack between six and eight times as much energy, in the neighborhood of 2,600 foot-pounds. Also, they tend to be much more sharply pointed than handgun bullets. The net result is, as can be seen in Figure 2 , below, that it’s difficult to predict where a rifle bullet will fly once it strikes a windshield.

Figure 2, Windshield Effect on Rifle Bullet

Figure 2, Windshield Effect on Rifle Bullet

3. Handgun vs. Automobile Body

The police have shown up, the bad guys are barricaded in the bank, and everyone’s shooting. The police take cover behind their car doors…

…and get shot. With rare exceptions (a note about them later), handgun bullets will go right through sheet metal car doors and their plastic and polyurethane liners. Typical bullets (9mm Parabellum, .40 S&W, .45 ACP, .357 Magnum) will fragment, yaw and break up as they penetrate the doors – but they will still penetrate the car – and the occupants. Worse for the occupants, they will take bits and pieces of the often filthy and bacteria-laden door innards with them.

The exception comes in the form of modern police vehicles where the department in question has purchased certain options. For example, the 2014 Ford Police Interceptor (built on the basis of the Ford Fusion sedan) can be ordered with ballistic door panels rated to National Institute of Justice (NIJ) Threat Level III. This means that the doors of police cars so equipped can stop 7.62mm NATO M80 ball rifle rounds moving at around 2,750 feet per second. However, this is not a standard feature and not all police cars have this feature.

Figure 3, Ballistic Door Panel Insert from Ford Police Interceptor

Figure 3, Ballistic Door Panel Insert from Ford Police Interceptor

4. Rifle vs. Automobile Body

With the exception of cars equipped with ballistic door inserts, automobile bodies offer no protection against modern rifle ammunition. The bullets zip right through doors and body panels – and right out the other side, merrily perforating the occupants inside. In fact, the only portions of an automobile that might realistically offer protection from small arms fire are the engine block and the steel brake rotors and rims.


5. Shotgun vs. Automobile Body

Shotgun shells contain a number of individual pellets. When fired, these pellets spread out into a pattern, increasing the likelihood of one or more hits on a target. A 12 gauge shotgun shell intended for defensive uses will typically be loaded with 00 (0.33” pellet diameter) or 000 (0.36” pellet diameter) buckshot. The pellets typically have a muzzle velocity akin to that of a fast pistol bullet (around 1,300 feet per second). As such, they generally act like handgun bullets, defeating car doors and occupants, but not exiting the vehicle. Moral of the story? Automobiles offer the same level of protection against shotgun blasts as they do against handguns – none.

Figure 4, Shotgun Effect on Automobile Occupant

Figure 4, Shotgun Effect on Automobile Occupant

Thumps in the Night (and Bang Bang Bang)

1. This Little Piggie Made Her House Out of Straw (Well, Wall Board at Any Rate)

As we’ve seen, cars won’t protect good guys and bad guys very much against modern small arms. What about houses? Let’s assume a typical residential or office building. The exterior walls may be of brick or concrete, but the interior subdivisions of the building are made from sheet rock or wall board.

The answer is short and simple: Modern handgun and rifle ammunition will easily penetrate six or more interior walls – and kill someone inside the seventh room, while wallboard offers only minor protection against shotgun ammunition. Experiments were conducted using twelve sheets of 5/8” wall board. The results are below:

Ammunition

Result

9mm Parabellum, 124 grain Ball

All 12 sheets penetrated

.45 ACP 230 grain Ball

All 12 sheets penetrated

.45 ACP 200 grain Jacketed Hollow Point

All 12 sheets penetrated

5.56mm M193 Ball (Rifle)

All 12 sheets penetrated

.308 Winchester (Rifle)

All 12 sheets penetrated

12 Gauge Shotgun (00 Buck)

8 sheets penetrated

Table 1, Handgun, Rifle and Shotgun Wallboard Penetration

2. This Little Piggie Made Her House Out of Wood

Things get a little more interesting when ¾” pine boards are substituted for sheet rock. In this test, 12 pine boards. This is atypical for most construction, but not so much as to be incredibly rare:

Ammunition

Result

9mm Parabellum, 124 grain Ball

8 boards penetrated

.45 ACP 230 grain Ball

7 boards penetrated

.45 ACP 200 grain Jacketed Hollow Point

7 boards penetrated

5.56mm M193 Ball (Rifle)

All 12 boards penetrated

.308 Winchester (Rifle)

All 12 boards penetrated

Table 2, Handgun and Rifle Wallboard Penetration

Conclusion

Your readers are counting on you to make your stories engaging and absorbing. One of the ways you can most rapidly lose that bubble is by failing to make your stories believable. The technical facts are that there’s really no protection offered by interior building materials from rifle fire, and only nominal protection against handgun and shotgun ammunition.

The moral of the story, however is that one of the quickest ways you can lose a reader is to make your story unbelievable. Attention to technical detail is important – and technical details include terminal ballistics. Safe shooting and happy writing!

***

Do you have any questions for Adam regarding terminal velocity – or other topics?

Join us Monday when CANDICE HUGHES discusses “Getting Inside the Mind and Culture of Medical, Science and Tech Characters”

***

Bio: Adam Firestone brings more than 25 years of experience with weapon systems including small arms, artillery, armor, area denial systems and precision guided munitions to Romance University. Additionally, Adam is an accomplished small arms instructor, editor, literary consultant and co-author of a recently published work on the production of rifles in the United States for Allied forces during the First World War.

Adam has been providing general and technical editing services to authors and publishing houses specializing in firearms books since the early 2000s. Additionally, Adam provides literary consulting services to fiction authors including action scene choreography, technical vetting and technical editing. In this line of experience, Adam has had the fortune to work with well known authors including Shannon McKenna and Elizabeth Jennings.

Check out Adam’s blog here: http://adamfirestoneconsultant.blogspot.com/


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Discussion

18 Responses to “Buildings and Automobiles and Guns, Oh My!: A Brief Discussion of Terminal Ballistics”

  1. Morning Adam!

    Well holy moly. I’d always wondered about the car door vs bullets…now I know!

    Is it true then that the windshield is actually harder for a bullet to penetrate than a car door? And what would be the best thing to hide behind if someone was shooting at you? I’ve seen them (in the movies) kick over an old wooden table, but your “little piggie” graphics make me rethink that….

    thanks for a super interesting post Adam….I’ll probably never look at movies the same way again!

    carrie

    Posted by Carrie Spencer | September 27, 2013, 8:40 am
    • Hi Carrie,

      Windshields are a) thick glass and b) sloped. Car doors are a) thin sheet metal and b) generally perpendicular to the bullet’s line of flight. SO yes, it’s generally easier to punch through a car door.

      Hide behind? Sandbags. Or maybe brick. Or stone. Or steel. If I’m behind a car, I’m getting behind the engine block or wheels.

      Hope that helps!

      Adam

      Posted by Adam Firestone | September 27, 2013, 11:09 am
  2. Thanks so much for this post, Adam! So many movies and TV shows have people hiding behind car doors, tables, sofas and other things that wouldn’t protect them in real life. I’m surprised they don’t get called on the inaccuracies more often! (Although this is hardly the only problem with a lack of accuracy. I mean, seriously, how many medical examiners wear heels to work?)

    Posted by Becke Martin Davis | September 27, 2013, 8:48 am
  3. Adam – I wouldn’t WANT to see anyone who’s been shot. Television and movies kind of dull our senses with all the graphic images, but without the smells and other things that make a real accident/shooting, etc. so powerful, it doesn’t cause such a visceral reaction. I think in some ways TV serves up what they think we expect scenes like that to look like, rather than the true image.

    Posted by Becke Martin Davis | September 27, 2013, 12:01 pm
  4. Wow, Adam, thank you so much for the wonderful information.

    I don’t know if you know anything about tasers. My hero is getting shot with a dart firing air taser. Any advice on getting the reaction real when shot from approximately 15 feet away?

    Posted by Carol Opalinski | September 27, 2013, 12:25 pm
  5. Adam,

    This is great info! When I watch movies with shootouts, I’m always wondering how the character can carry so many ammo clips on them and still run unencumbered. How much does a clip for a Beretta weigh?

    Posted by Jennifer Tanner | September 27, 2013, 7:26 pm
  6. Thanks so much for another eye-opener, Adam. This makes me wonder how many other things TV gets wrong – courtroom scenes, police and military slang, etc.

    The problem for authors is that readers may believe what they’ve seen on TV is true and realistic, and they may therefore question an accurate portrayal in a book.

    I can see it now – you should start a Snopes-like blog correcting misinformation from TV shows and movies. I bet a lot of people would be interested!

    Thanks again for joining us – and educating us! Have a wonderful weekend!

    Posted by Becke Martin Davis | September 27, 2013, 8:23 pm

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