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SIG Sauer BDX: One-stop Solution for Accurate Long-Range Shooting

1. The BDX app puts information in logical order. 2. Storage for 25 ballistic profiles means less prep and more shooting.

Cutting-edge technology built into rifles, optics and ballistic calculators are enabling long-range shooters to harvest astonishing group sizes at far greater distances than once ever imagined. However, the resulting stampede to market by manufacturers has given endusers — seasoned pros and new comers alike — a steep learning curve. What should you use? How can you take full advantage of the latest suite of precision-shooting technology? SIG Sauer has just made the process more intuitive and less expensive.

3. The bullet library has both the big brands and small shops included. 4. Applied Ballistics software goes to work once all the data is entered.

The One-Stop Shop

SIG Sauer's new line, called the Ballistic Data Xchange (BDX), takes the confusion out of selecting and using all the tools necessary to be a precision shooter. There are two components that require purchase: a scope and a rangefinder. Then, you download a free app to a smartphone for the complete hat trick.

5. Recalculating holds is almost instantaneous as new targets are ranged. 6. Holds are visually created for rapid acquisition and dialing should you lose the Bluetooth connection between scope and rangefinder.

What is BDX? The short answer is that it's a personal data-sharing network between your smartphone, a Kilo BDX rangefinder and a Sierra3 BDX riflescope. Through the use of Bluetooth technology, the rangefinder uses a shooter's ballistic information that's entered into the app to calculate the precise holdover of a target based on its ranging. It then communicates with the scope to paint a dot on where the holdover needs to be.

Fire control

The first step in using the system is building the "gun profile" in the application. SIG Sauer collaborated with Applied Ballistics on the app, so it is a tested and proven calculator. Here's how the system is set up:

Next step in setting up the system once the gun profile has been built is to pair the system to work together.

First, open the bullet library and scroll through the bullet inventory in the Applied Ballistics system. All the big boys are in there including Hornady, Nosler, Berger, Sierra, etc. There are even bullets from small custom makers. The likelihood of not finding what you're looking for is very low. Making a selection will automatically load the bullet diameter, weight and ballistic coefficient (BC) into the app. It is also possible to manually enter the BC, which is important should the shooter want to true the app to their rifle.

The shooter must also input the rifle's muzzle velocity and the range that the rifle was zeroed. I have seen hunters successfully use the muzzle velocity printed on ammunition boxes, but it will not exactly match what comes out of an individual's rifle. Shooting at least five rounds across a good chronograph will lead to a more accurate calculation.

Thanks to low-energy Bluetooth and other technological advancements, the rangefinder uses just one CR2 battery.

Once the gun profile is built, the next step is to pair a BDX-enabled rangefinder to the system. If you've ever paired your cell phone to your car or headphones, the process is similar. Once paired, an illuminated dot automatically appears with the correct hold in the scope after you laze a target with the rangefinder. Put the dot on the target, fire and you'll hit. There is a screen on the app that also allows you to see all the data the rangefinder and ballistic calculator are providing. Much of the same information is also visible in the rangefinder as well. The redundancy built into the BDX system is a blessing in the field.

Pinging a target will provide a shooter with conventional elevation and windage holds displayed on a smartphone and in the rangefinder in either mils or MOA at the same time as the illuminated dot appears in the scope. The app also displays the range to the target, the angle to the target and the bullet's energy and velocity at that impact distance, which is actually very useful. The rangefinder display screen on the app enables the shooter to manually input windspeed and direction along with temperature and elevation. Once entered into the app, temperature and altitude will apply to all gun profiles. These environmental factors will not update once the information is loaded into the rangefinder.

Sierra3 BDX lenses are coated with Spectracoat, SIG Sauer's coating that reduces reflections across the visible spectrum.

I recommend getting on the internet in the area you'll be hunting and looking at the Weather Underground website ( for the most recent conditions and forecast. I would look at what the high and low temps will be for the next day and then split the difference when setting up the app and rangefinder. The BDX system can also auto populate temperature and altitude from the cell phone, if you set it up that way. I prefer manual entry.

That's all there is to setting up the BDX system! Once the gun profile is saved in the app and the rangefinder and scope have been paired to it, there's nothing left to do but go shooting. Shooters don't even need to take their cell phone with them on the hunt or while shooting. All the ballistic calculator hardware and software lives inside the rangefinder. The app and cell phone are only necessary when managing gun profiles and pairing the rangefinder to any one profile.

Providing power for the Sierra3's dot illumination and other internal electronics requires two CR2032 batteries.

I found SIG Sauer's BDX to be the most painless, user-friendly, long-range system currently in existence. Inside 600 yards, it was exceptionally accurate.

Working the system. Any ballistic calculator is only as good as the information you give it. My test ammunition was Hornady's 140-grain Extremely Low Drag Match (ELD-M). Given that it's in the app's library, the information pulled up automatically when selected. Finally, I gathered my weather information and entered that into the BDX app before heading to the range.

Besides illumination control, parallax adjustments can be made using the inner dial to the distance being targeted.

Next came velocity and zeroing. Since I'm picky about what chronograph I use, I selected a LabRadar. LabRadar makes a trusted partner, but Magnetospeed and the Oehler 35P are also good choices. I shot 10 rounds across a LabRadar and entered that data into the BDX app.

For those that don't have a chronograph, the BDX system also works accurately by inputting the muzzle velocity listed on the box of ammo and then "truing" it at 600 yards. All that's required to true is to shoot at 600 yards, note how high or low the rounds impacted relative to where the BDX system predicted, and then enter that difference into the app's muzzle velocity adjuster.

When range is confirmed by the rangefinder, a blue LED light located on the power-adjustment ring will blink indicating the correct holdover has been calculated.

I confirmed zero at 100 yards on the new Christensen Arms Modern Precision Rifle (MPR). I then started banging steel from 200 to 600 yards to see how far I could push the BDX. At the touch of a button on the rangefinder, a small illuminated dot appeared on the vertical stadia of the scope's crosshair. It's point-and-shoot after that.

The BDX was designed for hunters and long-range shooters who desired simplicity and speed, and it works in that regard. However, I only recommend putting it on a rifle that has a tubular forend around the barrel when used in conjunction with the Kilo2400BDX rangefinder. The chassis guns make it necessary to alter sight height to get hits on target, especially as distances increase.

If the Bluetooth connection is lost in the field, windage and elevation can still be dialed using data procured from the app or the rangefinder.

On Sight Height

One detail about setting up a ballistic calculator for accurate shooting is sight height, or the distance between the centerline of the bore and the centerline (line of sight) of the scope.

I spoke with Andy York, president of SIG Sauer Electro-Optics, about sight height on the BDX system and asked if the shooter could input that data.

When considering the holdover and windage, the system utilizes 18 horizontal wind-hold indicators, 76 vertical segments and two LevelPlex indicators. The LevelPlex is a digital anticant system that's six-times more accurate than a typical bubble level.

"Just when using the 2400BDX," York replied. "Our goal is to provide an accurate and simple system. In pursuit of that balance, we fixed sight height on all other rangefinders at 1.75 inches. That is a very common height for most hunting rifles."

York is correct. Once the scope is mounted at 1.75 inches (or within a tenth of an inch of that height), it worked like a champ out to at least 600 yards on any hunting rifle. Shooters that use a chassis will need to use the BDX system with SIG Sauer's Kilo2400BDX rangefinder, as it is currently configured. I did not use a 2400BDX rangefinder with this chassis rifle during testing, which is why I saw some deviation past 300 yards.

York also said that SIG Sauer could do a software update at any time to allow the end-user to input their own sight height with all rangefinders. They will certainly do it if that's what the customer desires. My vote is to leave the system as it is. The BDX is a simple and elegant solution to long-range shooting for the rifle-wielding majority. Those wanting pinpoint accuracy out past 1,000 yards should use the Kilo2400BDX rangefinder.


Putting it all together.

A big selling card of the BDX system is that it allows shooters to buy one component at a time. For example, the fastest and cheapest way to see a big increase in your long-range shooting potential is to pick up the Kilo1400BDX rangefinder. It retails for $300 and has the Applied Ballistics Ultralite calculator built into it. When used with the free app, you can range your target. The hold you need to dial will pop up in the rangefinder. Dial whatever scope you're using and then shoot.

Until now the only product with similar capability was the Kilo2400ABS, and it retails for $1,800. The Kilo1400BDX won't get you out as far, but it's everything you need to shoot really accurately out to 600 yards in my opinion.


For readers untrusting of technology, rest assured that you won't be left hanging in the field. If for some unforeseen reason the Bluetooth link between the BDX scope and rangefinder stops working as the shot of a lifetime presents itself, you can still see the elevation you need to dial in the rangefinder. All you have to do is pull the elevation turret cap off the BDX scope and dial as usual.

The BDX system will do very well with the rapidly growing long-range community and with hunters who contend with longer ranges because of the speed and simplicity it offers. Along with the flexibility of only having to purchase a piece at a time and a wide range of models to choose from, there's a configuration to fit just about any budget.

SIG Sauer Sierra3 BDX

SIG Sauer Sierra3 BDX

Power: 6.5-20X

Objective: 52mm

Tube Diameter: 30mm

Elevation Adjustment: .25 MOA per click

Windage: .25 MOA per click

Reticle: BDX

Length: 14.4 in.

Weight: 1 lb., 10 oz.

Eye Relief: 3.7 in.

MSRP: $960

Manufacturer: SIG Sauer, 603-610-3000,

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