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Guns, Cars, VBGs and Night by Adam Firestone
Posted By Becke Martin Davis On April 23, 2014 @ 12:01 am In Gun Expert Adam Firestone,Monthly Columns/Labs,Romance University,Scene Construction | 2 Comments
Heeee’s baack! Every time Adam Firestone  comes back with his regular posts, I wonder what topic he will discuss. He always surprises me, and his posts always address issues that have spiked my curiosity. As a writer, I’m very grateful for Adam’s attention to detail. He knows how to make our fictional action scenes come to life, as you will see as Adam tackles the following scenario.
Guns, Cars, VBGs and Night
A writer once posed the following scenario to me, and I think it’s a fruitful topic, and one worth relating:
a. What kind of rifle and ammunition would the shooter use?
Analysis Part 1 – Location, Location, Location
There are few more things at issue here than choice of weapon. Specifically:
Solution Part 1
The shooter needs to position himself in a treeline, behind a bend in the road. For our purposes, let’s make this a two lane (one in either direction) rural road. The treeline (and the darkness) will provide him a concealed shooting position, while the 90 degree bend allows him to be directly behind the target vehicle without being in the roadway itself. Importantly, the 90 degree bend also forces the car to slow down to between 10 and 20 miles per hour, and then accelerate back to highway speed. This period of slow movement provides the shooter a window in which he can engage the target when it at a known distance.
Why is a known distance so important? Because of a little thing called GRAVITY. Bullets do not follow a straight path, like a laser. Instead, they fly in a ballistic arc, dropping in elevation as they get further from the gun’s muzzle. Shooters account for this by adjusting sights such that in order to look directly at the target, the firearm’s muzzle has to be raised to some degree above the horizontal, launching the bullet upwards so that it drops into the target. As an example, at a distance of 200 yards from the muzzle, a bullet fired from a rifle chambered for the .308 Winchester cartridge will drop almost eleven inches. By knowing the distance at which the shot is to be taken, the shooter can pre-set the range dials on his sights, compensating for drop over distance.
A schematic of an ideal setup for this scenario is shown below.
Analysis Part 2 – The Right Tools
There are four components to tool selection:
Interdependencies between all of these come into play for our shooter.
The target is a car. More specifically, it is a car WINDOW. Glass (tempered or otherwise) is an interesting substance. It’s extremely hard, and extremely brittle. Sure, it will shatter when struck, but it will also have very significant effects on projectiles as they pass through. A bullet in a typical hunting caliber (let’s say .308 Winchester, .30-06 or .30-30) will pass through, but will also be deflected unpredictably. There is also a significant chance of large scale deformation. It might continue straight, it might tumble, it might move up, down, left or right. As a result, the nature of the target has an impact (no pun intended) on our choice of ammunition.
Given the nature of the target and the potential effect it will have on projectiles, we can deduce a requirement for a projectile that will have minimal, if any, deflection when moving through read window glass. This narrows the selection scope to big, heavy, high speed projectiles.
It’s dark, but we have a relatively large amount of ambient light. What our shooter needs is some sort of optic that will intensify the ambient light and allow him to see his target clearly. Fortunately, there are many optics built around image intensifier tube technology. Image intensifier tubes convert low levels of light from various wavelengths into visible quantities of light at a single wavelength. This technology is available in many precision firearm optics.
The easy part, right? It’s got to be able to a) use a large cartridge that features a heavy projectile and b) mount an image intensification optic.
Solution Part 2
It’s a good thing that our shooter is a) well heeled and b) a former military sniper. The former means that we can kit him out with the objective solution system without worry about cost, while the latter means that he can plausibly have experience with the objective system. Without further ado, let’s introduce “the right tool for the job.”
The current US military long range sniper rifle is the Barrett M82A1, type classified by the Army as the M107. It is chambered for the .50 Browning Machine Gun (BMG) cartridge, and a number of specialized sniper rounds have been developed for it. Among these is the M1022 long range sniper cartridge, with an effective range of 1,800 meters. It uses a 670 grain (about 1.5 ounces) projectile with a muzzle velocity of about 2,800 feet per second. This means that at the 250 meter distance to the target in our scenario, the bullet will strike the window moving at around 2,450 feet per second with an energy of some 8,950 foot pounds. That’s a LOT of foot pounds. To put this in perspective, Dirty Harry’s .44 Magnum had an energy at the muzzle of about 1,200 foot pounds.
To get an idea of just how truly huge the .50 BMG is, take a look at the photo on the left. The cartridge on the left is the US military 5.56mm, used by the M16 series of rifles. The center cartridge is the .338 Lapua, considered a large, high performance round. The .50 BMG is on the right. As my Canadian friends might say, “Big, eh?”
For our scenario this means that the projectile will punch through the rear window as though it isn’t there and zip right through the windshield, creating a half-inch hole with lots of nice star shaped craze cracking.
I know what you’re thinking. But Adam, it’s DARK! How is he going to see the car? I saved the best for last. The M107 is frequently fitted with the AN/PVS-10 Sniper Night Sight, which couples image intensification technology with a 12.2 power telescopic sight.
Using this sight, the shooter will be able to see the target clearly, and, at 250 meters, be able to select the part of the window he wants to hit. The icing on the cake is the distance determination.
By putting an infrared ChemLite out on the road at precisely 250 meters from his shooting position, he’ll be able to know when the target is at the proper distance. Infrared ChemLites emit a glow that is invisible to the naked eye, but clearly seen with an image intensification device.
There are one or two other issues, such as the five to six foot width of the car, and the fact that about half of that is taken up by the occupants – but those are details that can be plausibly explained in the story.
Now that we’ve got our shooter set up and equipped to handle the physics of the scenario, we can identify the way things happen. The sequence of events works like this:
Do you need Adam Firestone’s advice for a particular scenario in your story? Don’t be shy – if your question is too complex for Adam to answer in the comment field, he might just use your question as the topic of a future post!
On Friday, RU founder Kelsey Browning presents, “Lessons Writers Can Learn from American Idol.”
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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 Buildings and Automobiles and Guns, Oh My!: A Brief Discussion of Terminal Ballistics: http://romanceuniversity.org/2013/09/27/buildings-and-automobiles-and-guns-oh-my-a-brief-discussion-of-terminal-ballistics/
 Accuracy Matters: Calibers, Cartridges and Kindles by Adam Firestone: http://romanceuniversity.org/2013/10/25/accuracy-matters-calibers-cartridges-and-kindles-by-adam-firestone/
 How “Automatic” Pistols Really Work by Adam Firestone: http://romanceuniversity.org/2014/05/23/how-automatic-pistols-really-work-by-adam-firestone/
 Shaken, Not Stirred: The British Military Martini, or a Saga of Victorian Steel by Adam Firestone: http://romanceuniversity.org/2014/02/28/weapons-expert-adam-firestone-2/
 What’s in a Name: Assault Rifles, Assault Weapons and the Deliberate Imprecision of Language by Adam Firestone: http://romanceuniversity.org/2013/01/21/whats-in-a-name-assault-rifles-assault-weapons-and-the-deliberate-imprecision-of-language-by-adam-firestone/
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