07/01/2013

Richard FairburnLaw Enforcement Firearms
with Richard Fairburn

'KISS ballistics' for police precision riflemen

Don’t overcomplicate things — it really is pretty simple stuff until you go beyond 400 yards

When firearms instructors and/or tactical cops call an officer a “shooter,” they’re generally referring to a precision rifleman — a sniper. I was a “shooter” before I was a police officer and rifles have always fascinated me. My first major writing project was the first police-specific rifle training book (with the zero-imagination title Police Rifles) in 1994. 

During the years I have engaged static targets at distances out to a mile and big game animals at more than a quarter mile (only under “ideal” conditions). 

Reading the atmospheric conditions, plugging them into your smart phone app, and making a first-round hit at long range is both a mental and physical challenge, and intensely satisfying. But, it has almost no relationship to the practical use of a precision rifle by a police sniper. 

Don’t Overcomplicate Things
I almost hear the collective gasps of police shooters across the country. 

“Blasphemy!” you say! 

A police sniper may be called on to make a surgically precise hostage rescue shot, so we must understand exterior ballistics to “the Nth degree!” Actually, you can take the fanaticism with ballistics science to the point where you might degrade your ability to make a good snap shot during a rapidly unfolding incident.

The sources vary, but it’s safe to say the “average” police sniper rifle shot is taken at less than 100 yards and patrol rifle shots are closer to the 25-yard mark. Even at the highly unusual police sniper distance of 300 yards, the factors needed for hair-splitting precision are few.

A prime example: Does the up/down firing angle really matter that much?

An Ordinary Example
Let’s run the numbers on a worst-case scenario. I work in a building which has an open balcony on the 13th floor. A “floor” is generally assumed to measure about 12.5 feet. That puts a criminal sniper on the balcony at a height of about 163 feet. 

There is a tree line at the far edge of a large adjacent parking lot, allowing a police sniper to make an unseen approach. From the tree line, the laser-measured distance to the balcony is almost exactly 200 yards (not an extreme distance). 

The angle of the shot calculates to 15.6° of up elevation, making the flat or “gravity” distance 192.5 yards. Assuming the standard sniper rifle/load — a .308 Winchester firing a 168gr OTM @ 2650 fps — the bullet will drop 4.2 inches (2 MOA) from a 100 yard zero. But, when firing at any angle other than flat, the bullet will drop less, so we need to calculate how much less. 

Whether you calculate the how-much-less value by using the gravity distance of 192.5 yards, or allow your external ballistics app to recalculate drop based on a 15.6° up angle, we get a drop value of from 3.65 to 3.8 inches, instead of the normal 4.2 inches (+1.85 MOA). 

So, to make a 200 yard shot to the 13th floor balcony, an angle so steep our shooter will need to fire from the hood of a pickup truck rather than flat on the deck, the difference in impact from our normal 200 yard setting will only be about a half-inch. 

Infinitely Small Values
Since the adjustments on your scope are either ¼ minute-of-angle or .1 MIL (½ to ¾ inch at 200 yards), we cannot mechanically correct for a difference that small!

By now some of you shooters have fired up your external ballistics apps and calculators and are ready to argue about the tenth-of-an-inch difference you got when running the problem I outlined. 

To which I answer, “KISS!”

When firing at extreme ranges, we must factor in variables such as the ambient temperature, humidity, barometric pressure, spin drift (caused by the rifling twist rate), the Coriolis effect (caused by the rotation of the earth) … and maybe even the wind direction change caused by a butterfly farting on a flower 100 yards behind us. But, for this precision police sniper shot, those values are too infinitely small to even calculate, just as the up/down elevation correction is too insignificant for concern.

Laser range your target, dial in the elevation correction you’ve already determined many times from live fire, make any necessary allowances for the wind, and get a nice, clean break on the trigger. Don’t overcomplicate things — it really is pretty simple stuff until you go beyond 400 yards. 

Distance, wind, and SHOOT! Now, a 10 mile-per-hour wind WILL move your point of impact 3.3 inches at 200 yards, so you must make that correction. Amateurs worry about bullet trajectory, professionals worry about the wind.

Calculating the windage and elevation for various ranges can also be greatly simplified, but that’s for another column.

About the author

Dick Fairburn has more than 30 years of law enforcement experience in both Illinois and Wyoming, working patrol, investigations and administrative assignments. Dick has also served as a Criminal Intelligence Analyst and as the Section Chief of a major academy's Firearms Training Unit and Critical Incident training program. He has a B.S. in Law Enforcement Administration from Western Illinois University and was the Valedictorian of his recruit class at the Illinois State Police Academy. He has published more than 100 feature articles and two books: Police Rifles and Building a Better Gunfighter.

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