Sightron SIIB Big Sky 3-12x42mm Riflescope

By Chuck Hawks

Sightron SIIB 3-12x42mm
Illustration courtesy of Sightron.

This is one of Sightron's fine Big Sky line of premium riflescopes. Having previously used and reviewed several SIIB riflescopes (see the Scopes and Sport Optics - Reviews index page), we are generally familiar with the line. As regular Guns and Shooting Online readers probably know, Sightron's Big Sky line incorporates the following features:

ExacTrack: This scope features Sightron's unique ExacTrack windage and elevation adjustment system. No other system on the market comes close to the precision and performance of ExacTrack.

All Weather Construction: This scope features the ultimate in all weather construction. They are waterproof, nitrogen filled and provide a lifetime of internal fog protection for inclement weather.

Fingertip, Resettable Windage and Elevation: The round knurled dials are complete with positive clicks and are resettable providing all the precision needed to complement your Sightron scope. Available on select SIII Series and SII Big Sky Series Riflescopes.

Zact-7 Revcoat Multi-Coating: All Sightron SII Big Sky Series Riflescopes feature ZACT-7 seven layer multi-coating with precision ground glass. These lenses provide superior light transmission and resolution for the ultimate in performance.

Lifetime Warranty: Sightron is so confident in the quality of our products that we offer a Lifetime Warranty.

In addition to those proprietary Sightron features, it is worth noting that the SIIB 3-12x42 is not produced in some third world country. It is made in Japan, a first world nation world famous for optical excellence. (Sightron is the sport optics brand of one of Japan's best known optical manufacturers.)

It is built on a one inch diameter, one-piece, aluminum alloy main tube that is fully internally blackened. It has 1/4 MOA windage and elevation adjustments. The eye relief is a non-critical four inches. The reticle in the test scope is a well executed Duplex type. It is shipped with a cloth storage bag and premium lens caps.

All that is missing is a lens hood, which is available from Sightron ( for a reasonable $29.95. I know it is swimming upstream, but all camera lenses, riflescopes and telescopes should be equipped with a lens hood (sun shade). The hood increases color saturation and contrast, as well as protecting the front lens element.


  • Model: SIIB31242
  • Item number: 63009
  • Magnification: 3-12x
  • Objective diameter: 42mm
  • Field of view at 100 yards: 31.9 ft. (3x) to 8 ft. (12x)
  • Eye relief: 3.9-4.2 in.
  • Reticle: Duplex
  • Click value: 1/4 in. at 100 yards
  • Minutes per revolution: 15
  • W/E travel at 100 yards: 70 in.
  • Knob style: Hunting, resettable
  • Parallax adjustment: 100 yards (fixed)
  • Weight: 13.4 ounces
  • Length: 12.56 in.
  • Main tube diameter: 1 in.
  • Country of origin: Japan
  • 2015 MSRP: $739

As you would expect for a riflescope in this price class, the zoom ring turns with just the right amount of friction. It is easily adjusted, even when wearing gloves, but stays put and will not be inadvertently changed.

The fingertip windage and elevation adjustments click precisely. I found them to be accurate and repeatable, which definitely saves ammo when sighting-in a hunting rifle. The low turret caps avoid unnecessary bulk.

The ocular focuses to the shooters eye on fine threads and is retained by a locking ring, in the American pattern. I find this less convenient than fast Euro-style focusing, but it is admittedly less prone to inadvertent change.

The main tube wears a matte black finish. The Sightron "S" logo on the left side of the adjustment turret, the numbers engraved on the zoom ring and the model designation engraved around the front of the objective bell are copper-tone filled, not screen printed. There are no distracting, gratuitous graphics.

Looking through this SIIB in its most useful 3x to 7x magnification range reveals crisp, clear, contrasty views of the target that are sharp almost all the way to the edge of the field of view. As the magnification is increased to the maximum 12x setting, there is some understandable image degradation, particularly in decreased contrast.

Advertising claims aside, when riflescope zoom ranges are stretched beyond about 3:1, given the limitations of acceptable consumer retail prices and the current state of the art, image quality inevitably suffers, usually at the high magnification end of the zoom range.

Distortion is well controlled. It is difficult to check for lens flare and internal reflections in rainy Western Oregon in winter time, but I know from experience that Sightron's Zact-7 Revcoat full multicoatings work as claimed to minimize flare.

The approximately four inches of eye relief provided by the SIIB is appreciated, especially for use on a powerful magnum rifle. With an eye relief variation of only 3.9-4.2 inches throughout the magnification range, it is not necessary to change one's head position as the zoom ring is rotated.

Overall, this is good performance in a riflescope with such a wide magnification range. If you miss the target, you are not going to be able to blame this scope.

I requested a riflescope with a one inch main tube for a standard grade .30-06 test rifle from my friends at Sightron. I was thinking along the lines of a nice little S1 Hunter 2-7x35mm or 1.75-4x32mm, which is all the scope necessary for any reasonable big game hunting with what is basically an inexpensive .30-06.

When the SIIB 3-12x42 arrived, I simply could not bring myself to mount it on a relatively inexpensive rifle with an injection molded stock. This much scope deserves a rifle that can benefit from its extended capability.

Perhaps the most logical choice for a riflescope with a 3-12x magnification range would be a dual purpose (varmint and medium game) rifle in calibers such as .243 Winchester, 6mm Remington, .240 Wby. Magnum, .257 Roberts or .25-06. 3x provides an adequate field of view for hunting large animals in the woods and 12x provides sufficient magnification for long range shooting at pesky rodents.

However, I decided on a restored and enhanced Weatherby Mark V Deluxe .270 WM. This beautiful rifle has received some TLC at the hands of Guns and Shooting Online Gunsmithing Editor Rocky Hays. It was already wearing an entirely adequate Nikon Buckmaster 3-9x40mm Riflescope, but what the heck, an upgrade to the SIIB 3-12x42 makes a great hunting rifle even better.

The mounting space between the front and rear bells and the adjustment turret is generous. It was not a problem to mount the Sightron on the long Weatherby Mark V Magnum action.

It is worth noting that, although the Sightron 3-12x42 is longer than the Nikon 3-9x40, the two scopes weigh the same. The SIIB did not alter the rifle's balance and handling, a credit to Sightron's design and engineering.

Not being a fan of long range shooting at living animals, I will never come close to exceeding the 326 yard MPBR (+/- 3 inches) of the .270 Weatherby/130 grain factory load, so 12x magnification could be considered over-kill. However, good optics are always appreciated and I tend to think of this as, among other things, an excellent pronghorn antelope rifle.

As Class 2 animals go, pronghorn are small and they tend to live in open country where they can make the best use of their excellent eyesight to spot hunters and other predators at long distances. A scope like the Sightron SIIB 3-12x42mm can help to equalize the situation.

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Copyright 2015 by Chuck Hawks. All rights reserved.