Rifles > News

Ballistic Software for Long-Range Shooting

Much like going from a slide rule to an iMac, today’s software for mobile devices can take the guesswork out of windage and elevation settings for long-range ballistic solutions.

Two years ago, shooting alongside veteran Marine sniper Steve Reichert, I thought I’d accomplished something: Using handwritten ballistic data cards, I scored first-round hits on steel targets across a wooded valley at 1,000 and 1,400 yards. Despite his fancy handheld ballistic computer, Reichert missed both targets. Unperturbed, he punched two corrections into his Trimble Nomad computer and from then on, during several days of shooting, never missed—that is to say he didn’t miss another target at any distance. I knew, then, it was time to take a closer look at today’s advanced ballistic software.

Unlike a desktop computer ballistic program that generates drop, wind drift and time-of-flight tables, modern ballistic software incorporates all the shooter’s specifics—rifle, barrel length, twist-rate, scope details, ammunition details, etc.—and then, based upon the target (distance, angle up or down, moving or stationary) and the atmospherics (altitude, temperature, barometric pressure, wind direction and speed) it calculates the exact elevation and windage settings for a direct hit.

Such precision is unattainable with handwritten cards or manual calculations. For example, most shooters equate one minute of angle (m.o.a.) to 1.047" at 100 yards; however, some of today’s software uses the more exact 1.047197580733" and similar precision for many other factors. Shooting less than 500 yards, many shooters don’t need such computational assistance; beyond 500 yards, it becomes very useful; beyond 1,000 yards. it dramatically increases the likelihood of a hit.

Field Firing Solutions
The first program I examined was “Field Firing Solutions, Version Delta V,” loaded in a field-rugged Trimble Nomad handheld computer, the same as Steve Reichert used and with which he has fired his .338 Lapua Mag. rifle accurately to 2000 yards. Everything about the software demands and yields precision. Instead of lasing 100 yards for my initial zero, I was instructed to tape-measure it—remember, a laser is accurate “only” to within one yard. And I was required to measure not from my muzzle but from my scope’s elevation knob, the exact spot where a shooter applies elevation and windage changes.

Elevation knobs are inherently inconsistent, I learned—which is what inspired the software developer, Blaine Fields. Back in 2002 he had problems matching his new scope’s Bullet Drop Compensator to his rifle’s trajectory. Devising a simple computer program, he found that instead of the knob rotating 1/2 m.o.a. per click, it was actually 0.489 m.o.a. After solving that discrepancy he just kept going. “The program just took on a life of its own,” he explained. Following his procedures, I determined my scope’s precise click-value.

The Field Firing Solutions software contains a bullet database of nearly 3,500 entries, with room to enter custom loads, too. Many ballistic programs use only a bullet’s G1 Drag Model to produce a Ballistic Coefficient (BC), but Fields knew a bullet’s drag increases as it slows, lowering its BC, while today’s Very Low Drag bullets demand a low-drag G7 Model. Thus, his software employs multiple “stepped” Drag Models, which vary with bullet shape, length, weight and velocity at various distances.

Instead of entering the cartridge manufacturer’s muzzle velocity or measuring it with a chronograph—Field has found both slightly inaccurate—he had me test-fire at several distances, a process called “trueing”—to determine exactly how high or low my hit compared to the computer-generated point of aim. “The program will take this point of impact, compare it to the point of aim and then calculate a muzzle velocity which corresponds to that actual point of impact,” he explained. In one more step, I determined the velocity error factor and the software calculated the bullet’s BC. With that input, the software traced an updated trajectory that was “true,” reflecting my bullet’s precise arc, calibrating it to my scope’s click value.

Along with the corrected muzzle velocity and BC, I entered barrel length, twist-rate and direction of twist, and the exact height of the scope’s optical axis above the bore axis. All these details became a “profile” for that particular rifle, scope and cartridge, ready to be called up whenever needed. What if I wanted to profile another load or another rifle? According to Field, his program can store nearly 2 million such profiles.

It’s only when you reach a shooting location that you add more data, beginning with atmospherics. I obtained those from a Kestral 2500 electronic weather gauge—altitude, temperature, barometric pressure, humidity, station pressure, and wind direction and speed, entering it manually. The program can interpose three winds simultaneously, as well as consider vertical wind deflection from mountain updrafts and downdrafts. The atmospherics don’t usually change so long as a shooter stays at one location, but they can be updated at any time.

Now, add your target—its range, its angle uphill or downhill, whether it’s stationary or moving and to what degree. In a split-second the software calculates all winds, the atmospherics, range, up/down slant, target movement, spin drift (the tendency for a bullet to drift in the direction of its rifling), even the slight Coriolis effect caused by the earth’s rotation. The elevation and windage solution is offered as eighths, quarters or halves of one m.o.a., as 10ths of one mil, or as centimeters. To hasten engagement times, you can create a Target Range Card with a reference target for instantly shifting from one target’s firing solution to another.

“Field Firing Solutions is like having a very knowledgeable coach looking over your shoulder to answer questions,” says retired Phoenix SWAT officer Giles Stock, a 32-year instructor at Arizona’s Gunsite Academy and one of America’s most knowledgeable tactical rifle authorities. He has taken the system a step further, using his Trimble Nomad’s Bluetooth feature to automatically monitor and update atmospherics from a Kestral 4500 weather gauge, and to instantly input target data from Vector laser-ranging binoculars. It’s an incredible capability. Using the setup, he’s had rifle students score first-round hits to 2,200 yards. Marine sniper Reichert regularly does the same to well over a mile. Field Firing Solutions software is used by some of the world’s most elite special operations units as well as American police SWAT teams.

Instead of dialing computer-driven solutions on target knobs, some shooters employ riflescopes with a Horus reticle, a uniform grid that takes mil-dots to the next level. Arrayed as precise 1/5th mil aiming lines and dots, a Horus reticle appears confusingly busy—until you understand it. After that, you simply aim with the dot indicated by the ballistic software, never lifting your head away from the scope or rotating knobs. The combination of software and reticle make shooting multiple targets remarkably fast and impressively accurate.

Horus ATRAG Software
Horus also offers its own advanced ballistic software, ATRAG, the second program I explored. I was introduced to ATRAG this year while training with 101st Airborne Division snipers at Ft. Campbell, Ky., just before they deployed to Afghanistan. According to Brian Mellado of Horus Vision, the company won a U.S. Army contract for 2,700 Advanced Ballistic Calculator kits containing ATRAG software in a sturdy Trimble Recon handheld computer.

Snipers of the 101st Airborne’s 1st Battalion, 506th Infantry, have trained extensively with ATRAG’s MX military version and are now using it daily in combat. Having already used Field Firing Solutions, I could appreciate the importance of ATRAG’s similar “trueing” of the trajectory curve—and concluded that ballistic software must include “trueing” to achieve accuracy. ATRAG operates a great deal like Field Firing Solutions but for a number of nuanced differences; for instance, ATRAG does not consider a bullet’s length, which can affect spin drift calculations. Also, ATRAG employs the “clock” system for entering wind direction, while Field Firing Solutions uses exact degrees.

The “Screaming Eagle” snipers use ATRAG calculations both as knob settings and as Horus reticle holds, depending on the situation. “There is a time and place for both dialing and holding,” explained the platoon’s senior sniper, “but we greatly prefer using holds with the Horus reticle. In a kinetic [shooting] environment that requires rapid engagements, the Horus reticle provides a great platform for not only first-round hits but for fast follow-on shots and corrections.”

1   2    NEXT >>

Share |

Comments

ADD YOUR COMMENT

Enter your comments below, they will appear within 24 hours


Your Name


Your Email


Your Comment

2 Responses to Ballistic Software for Long-Range Shooting

Steve Lewis wrote:
December 13, 2013

Good morning. Great article by Mr. Plaster on 11 Dec. He mentioned also considering 'even the slight Coriolis effect caused by the earth’s rotation' Could you please provide some insight into the coriolis effect on the impact point when shooting directly East vs West and whether the effect would be horizontal or vertical. There have been some interesting TV statements about the coriolis effect lately. Thank you very much. Steve

Mike wrote:
December 12, 2013

Looks good. $400+ is a bit much. Was hoping for an article for the everyday guy/gal.