SIG Sauer Sierra6 BDX (Ballistic Data Xchange) Scope: Review

My most common reaction to new technology is “I don’t need it.” New technology requires me to mess with something with which I am unfamiliar and, frequently, I find that I’m no better off than I was before the new widget came into my life. However, sometimes technology brings with it a huge increase in capability or convenience. Smartphones are a prime example. Like the smartphone, SIG Sauer’s latest BDX, the Sierra6, brings both capability and convenience.

One principle that governs SIG’s approach to its newest BDX is the concept of phased integration. New technology can be intimidating, so it is best to take it on a little at a time. Neophytes will be able to use this new scope as a standalone optic on their rifle; paired with a free app on their cell phone; or together with the smart device and one of SIG Sauer’s BDX laser rangefinders. Structuring the Sierra6 BDX system this way allows the product to fit a variety of consumer needs.

A “smart” scope?

While the technology and manufacturing of riflescopes has changed considerably in the past 20 years, what scopes do for the shooter hasn’t changed that much at all. A scope allows the shooter to better see the target and, thanks to magnification, develop a more precise point of aim. Reticles have changed to suit shooter preference, and now offer multiple aiming points. However, even new reticles function the same way they always have.

SIG Sauer’s BDX systems represent a significant change to riflescopes. These aren’t the first optics to provide an electronic aiming point (or points) for the rifles they top, but they are the most elegant and easily ­operated. The subject of this review, the Sierra6 BDX 3-18x44mm is a SIG-designed magnified optic with a 6X erector assembly. Being able to move from 3X to 18X with the flick of a wrist gives this scope appropriate magnification for 90 ­percent of rifle-shooting scenarios. The elevation and windage turrets are capped and adjust in .25-MOA increments for sight-in. Guns & Ammo’s test scope has a 44mm objective lens, a 30mm maintube, and came with a removable power-ring throw lever installed. The scope has adjustable focus which can be used on targets as close as 50 yards.

Two CR2032 batteries power the optic. These are almost as common as AA and AAA batteries, and available everywhere. Two CR2032s provide the juice needed to power the illuminated reticle system as well as the Bluetooth connectivity to cell phones and laser rangefinders, if utilized.

I spoke with SIG Sauer’s Electro-Optics division about the Sierra6 scopes and asked how long the batteries last. The answer was complicated because every BDX scope has Motion Activated Illumination (MOTAC), a sensor system that turns the scope off after it hasn’t moved from 1 to 5 minutes; the customer chooses. As soon as the optic moves, it powers on instantly. The other battery-saving feature is a “Hard Timeout.” This kicks in after anywhere from 30 minutes to 8 hours, depending on when or if the customer sets it. Once the set time passes, the optic shuts off. Turning the power magnification ring or the side-focus/cartridge-family-setting turret immediately turns the optic on. Typical use that leverages these battery-saving features results in a battery life of around 1 to 2 years. If you shut off all the battery ­saving features and use the optic non-stop so MOTAC doesn’t kick in, battery life is 200 hours. Interestingly, the feature that drains the battery the most is the blue light on top of the ocular housing. Putting the optic in “battery ­saver mode” on the app turns this light off.

One of SIG Sauer’s priorities for the latest Sierra6 BDX was to make them “standalone” solutions. This allows the customer to drop the scope on any rifle; it’ll work as designed. No additional purchases or technology is necessary. Even in this most basic-use case, the Sierra6 BDX adds a lot of capability to any rifle. Close inspection of the turret holding the batteries shows 10 settings that some might mistake for illumination levels. However, the marks on the focus/battery turret actually determine what ballistic group the shooter would like to use with the scope. There is a guide that is readily available on the internet, and it ships with each scope. It categorizes rifle cartridges based on caliber, bullet weight and velocity. There are about 10 to 12 choices in each group, so there’s a high probability that your pet cartridge is on the list. For this example, let’s say I’m shooting a 6.5 Creedmoor with a 140-grain bullet at 2,742 feet per second (fps). That puts me in “Group 4” for the optic.

The owner’s manual covers the simple process to set Group 4 in the scope, so the next step is to zero the optic at 100 yards. Once that’s done, there is an illuminated dot at the center of the crosshair, as well as an illuminated dot for the 200-, 300-, 400-, and 500-yard holds.

If the customer doesn’t mind using the Sierra6 BDX with the free BDX app, the options for using the scope increase significantly. It becomes possible to build a custom rifle profile in the app that includes choosing the exact bullet from a bullet library. This allows the program to draw on the tested ballistic coefficient (BC) of that bullet and the actual muzzle velocity as entered by the customer — hopefully, after using a chronograph. (If no chronograph is available, use the velocity on the cartridge box.) The customer also enters the sight height, or distance from centerline axis of the bore to centerline axis of the scope. Once the app has that information, the scope can be configured in a number of ways. The shooter can set the seven or eight aiming points to correspond to fixed MOA or mil values, or the dots can correspond to each 100-yard mark out to 800 yards. Each of those illuminated dots can be turned on or off manually in the app.

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Should the customer desire maximum utility from the Sierra6 scope, using the app and pairing the scope with a SIG Sauer BDX rangefinder unlocks all of the system’s capabilities. When paired with the rangefinder, the customer can enter wind speed and direction and, once the laser measures the distance to the target, two dots illuminate on the reticle. One dot is on the vertical crosshair and corrects for elevation. The second dot is on the horizontal crosshair and shows the wind correction.

The New

The Sierra6’s predecessor, the Sierra3, has been available for a few years. It taught the company a few lessons on what needed improvement. SIG listened to their customers and incorporated their feedback into the Sierra6 design.

I spoke with Andy York, president of SIG Sauer Electro-Optics. “One of our priorities was improving image quality of the scope,” he said. “So the Sierra6 optical designs were done in-house by Brad Brumfield. They offer exceptional image quality. Additionally, we wanted to slim down the reticle and illuminated aiming points so they covered less of the target.” Another of SIG’s goals for the Sierra6 was to make it more useful for the competitive rifle shooting segment. The company doubled the number of aiming points in the optic as part of this strategy. Finally, SIG moved the Bluetooth antenna to the top of the ocular housing and upgraded the transmitter. Where the old Sierra3 had a maximum pairing range of about 10 yards, the Sierra6 has a range of up to 50 yards.

As part of my testing, I used a Sierra6 BDX on the Howa rifle in 6.5 Grendel, also reviewed this month. I wanted to assess the scope independent of any other equipment, so I mounted and zeroed it, and then moved to steel targets staggered at 100-yard increments out to 500 yards. There is no category that lists the 6.5 Grendel because it’s not one of the most popular cartridges. So, I estimated that it would fit best in Category 6. Category 5 had a listing for a .260 Remington which is quite a bit faster, so I bumped the category up one and headed out to ding some steel. It didn’t take long for me realize that Group 6 wasn’t a good fit for my rifle and cartridge combination. After five rounds, I saw impacts hit lower and lower on the steel targets at 500 yards. I switched to Group 7, which is normally reserved for muzzleloaders, and that one was almost perfect. I was about 2 inches high at 300 yards and about 5 inches high at 500 yards. Considering the max distance I’d shoot a 6.5 Grendel at whitetail deer is about 300 yards, this scope works perfectly for that task.

SIG Sauer’s Sierra6 BDX provides more accessible and relevant technology than any other scope of this type. Additionally, the image quality makes this scope a good buy — even without all the features built into it. This Sierra6 is a worthy candidate for anyone looking for an adaptable and accurate holdover reticle that works just as well independently as it does with SIG’s cutting-edge rangefinders and apps.

SIG Sauer Sierra6 BDX 3-18X44MM Specifications

• Power: 3X-18X
• Objective: 44mm
• Tube Diameter: 30mm
• Elevation Adjustment: .25 MOA per click
• Windage Adjustment: .25 MOA per click
• Reticle: BDX
• Length: 11.9 in.
• Weight: 1 lb., 7.8 oz.
• Eye Relief: 3.7 in.
• MSRP: $1,100
• Manfacturer: SIG Sauer, 603-610-3000, sigsauer.com