• Manufacturer: Sightron
  • Model: SIII 25143
  • Model Number: SIII10X42MMD
  • Finish: Matte Black Anodizing
  • Magnification Range: 10.0
  • Objective: 42mm
  • Tube Diameter: 30mm
  • Eye Relief: 3.6" (91mm)
  • Click Value: .25 MOA
  • FOV: 10.0' @ 100 yards
  • Adjustment Range: 150 MOA
  • Reticle: Modified Mildot
  • Focal Plane: Fixed Power
  • Weight: 19.4oz (550 g)
  • Overall Length: 13.19" (335mm)
  • List Price: $ 899
  • Street Price: $ 599
  • Buy Here:

For nearly the entire 20th century, the fixed power day optic sight (DOS) was the mainstay of the military sniper weapon system. The simple operation of a fixed power scope combined with improved durability due to fewer moving parts and reliable performance gave the fixed power scope a distinct advantage over the variable power scopes. This remained the case up until about the year 2000 when the major players in the sniping community began to adopt high quality variable power scopes. The Schmidt & Bender 3-12x PMII scope replaced the legendary Unertl 10x scope on the USMC M40 rifles. The Leupold Mark 4 M2 3.5-10x scope was selected on the US Army M110 SASS rifle platform. The adoption of these scopes, as well as others, opened the floodgates to the adoption of the variable power scopes for the majority of the military issued DOS today. As manufacturing capability has improved over the years the manufacturing shortcomings of the variable power scopes were gradually overcome and the improved flexibility of variable power scopes have now prevailed. But there is still some value to the simplicity of a fixed power scope and while the durability of variable power scopes has been drastically improved, it will never quite reach the same level of the fix power scope. So it is here that we are reviewing one of the few remaining fixed power tactical scopes that can be found on the market today. This one is the Sightron SIII fixed 10x42mm tactical rifle scope and you almost have to purposely go looking for it to find it in their catalog. We decided it would be a good scope to put through the same tests that we normally do and see how it fairs and if there still might be a place today for fixed powered DOS on top of modern sniper weapon systems.

The packaging is typical Sightron SIII packaging with a nice box and an instruction booklet. They also provide a handy mil chart card to help with some of the basic calculations and uses of the mil style reticles. It is large so you likely will not be carrying it with you into the field, but it does provide some useful data if you are just learning to use the mil capabilities of a scope. The scope itself does not come with any scope caps, flip up or otherwise. But there is a “ScopeCoat” style neoprene cover that can be used to protect the lenses and the scope when the rifle is stored.

The SIII 10x has a fast focus eyepiece that is typical on many scopes today. There is no locking ring on it and it spans the entire adjustment range in about 1.4 rotations. There is not any sort of markings or indicator line on the eyepiece to provide a reference to be able to move it to a predetermined setting. This typically is not a problem as the dioptre adjustment normally gets set once and then is left alone. Most shooters with corrected or uncorrected 20/20 vision will have a very similar setting for the dioptre, so not a lot of adjustments are needed. There is a medium amount of resistance when rotating the eyepiece and it is fairly smooth, though not as smooth as others we have tested. For durability reasons, we would prefer to see a fine focus ocular on a fixed power scope like this one in order to make it as rugged as possible, but we did noticed that this eyepiece shows no signs of looseness or weakness.

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In front of the eyepiece the ocular lens housing actually has a rounded egg shape taper to it which is a bit different from other scopes, but it does look nice. Just in front of the ocular housing, where the normal zoom power adjustment ring would be located, you will find an adjustable parallax control. There are very few scopes on the market today that have the focus adjustment located here, the SWFA SS series of scopes being the other ones that come to mind. It obviously can only work on a fixed power scope, but the location is actually handy and well located. The side focus is perhaps a bit more convenient because the twisting motion on a side focus adjustment is a bit more natural than it is with it located at the rear of the scope. The adjustment range of the parallax adjustment only covers 50% of the control knob and half of that is taken with the 10 to 50 yard settings. For a scope like this that is intended for tactical long range use, adjusting the control to go from perhaps 50 yards to infinity, instead of 10 yards, and then distributing the focus range over that half of rotation might be a more precise and effective way of doing it. The focus still works well enough, but it could be tweaked a bit for even better results.

The “rear focus” control itself rotates smooth through the range and feels very much like a zoom power adjustment ring. There is some basic knurling on the control ring to help with gripping it, though it is not very aggressive. There is a single small indicator dot on the eyepiece to help align the focus ring and there are some yardage markings squished onto the ring going from 10 on up to infinity. There is a good amount of resistance on the ring to keep it held in place when it is not being adjusted and while this focus knob it is a bit different in terms of location, the parallax adjustment does work well. We have read a report in the past that indicated the rear focus may actually be the most precise and best place to locate the adjustment in terms of mechanical design, but we have no proof ourselves that that is the case.

In front of the parallax, or focus, adjustment ring there is 2.1″ of tube length for which to locate your rear scope mounting ring. The tube is a 30mm diameter tube and at the front of the mounting area the tube blends nicely into a rounded shoulder area where the elevation and windage adjustment knobs are located. The shoulder area itself is not large, providing just enough area to elevate the knobs and to house the internal mechanisms.

Both the windage and elevation knobs are an exposed tactical style large knob. The elevation knob has a similar knurling on the top that is found on the parallax adjustment ring, it is not overly aggressive, but it does provide some good grip. The markings are in a bronze color that matches the markings on the rest of the scope and does give it a bit of subdued tactical appearance. There is a decent amount of marking area on the knob, of which a lot of it is used by some tall hash marks. The numbers are clear and easy to read and the knob has 15 MOA of elevation per rotation. The amazing thing about this scope, and something that being a fixed power scope aids with, is that there is 150+ MOA of total elevation adjustment!. Our test scope actually had 153. That is an extreme amount of elevation and it allows this scope to be mounted with a flat, uncanted base and still have plenty of elevation to take a 308 shooting 175gr ammo from 100 to well over 1300 yards. Again, that is WITHOUT a canted base. Add a 20 or 40 MOA cant and you are talking extreme ranges, though the scope only has 10x of magnification. The clicks themselves are a nice click with minimal slop and with a good firm tactile feel to them. There are horizontal hash marks beneath the elevation knob to help track how many rotations have been dialed into the scope, which will be needed with the extreme amount of elevation adjustments available and with there not being any sort of zero stop feature.

There is an up arrow indicator on the top of the knob to help remind the operator which way to dial the knob to move the impact of the round up. There are also three set screws around the top of the knob that can be loosened in order to “slip” the knob to zero once the scope and rifle have been zeroed. It should be noted that the knobs are in MOA and the reticle is a MIL reticle and this is the only configuration the scope is available in. Is this a show stopper? No, not at all. Sometimes things get blown out of proportion and the requirement that a scope have the same units for the knobs and the reticle we believe is one of those things. An operator can be just as effective with a scope setup with MIL/MOA as they can be with a MIL/MIL or MOA/MOA scope. It is a matter of learning your rifle and optics and then mastering them. We have used all of the possible reticle/knob combinations and can testify to the effectiveness of all of them.

The windage knob is the same size and shape as the elevation knob and it has the same markings in terms of font and color with the same large hash marks. The windage knob only counts up in one direction, to the right, and it too has 15 MOA of adjustments per revolution. We do prefer that the windage knob count up in both directions to help with ease of dialing in and tracking windage corrections. But we have used scopes that this is not the case and there are plenty of them out there this way and they are perfectly functional and effective once the operator is familiar with the setup. In fact, this was the way all the scopes were up until about a decade ago. Adapt and overcome… with training.

There are no controls on the left hand side of the scope where a side focus normally would be located, and there is no illuminated reticle either. In front of the shoulder area of the scope is another 2.0″ of tube length for mounting the forward scope ring and then the scope tube tapers up into the bell housing that holds the objective lens. The bell is threaded to accept a sunshade which is available as a separate accessory from Sightron. The objective lens is set back into the housing about 7/8″ which acts as a partial sunshade itself. With the 42mm objective lens size, the bell is fairly small which means the scope can be mounted nice and low on the rifle.

The overall fit and finish of the scope is nice with an evenly applied high quality matte black anodized finish applied over the entire scope. The scope itself is not large at all, only being a bit over 13″ long and weighs just 19.4 ounces (1.21 lbs). The simplistic operations of the fixed power scope and semi-compact size make the scope a good candidate for a field rifle that may need to cover lots of ground and be used quickly to engage targets. The overall lines and proportions of the scope look nice and it has a nice clean look to it.

With the initial examination of the scope completed, it was time to begin the operational evaluation of the scope. To find out more about how we test our scopes, please visit our how we test page. For this scope, we mounted it on top of our normal Remington 700 test rifle that we have used for many scope evaluations and it continues to serve us well. We used a set of Leupold Mk4 steel rings and the standard warne 20 MOA canted steel base we have had on the rifle for a long time. With everything mounted up it was time to head to the range and check the shooting performance of the scope.

The weather was typical Montana late winter weather with the temp right about 30 degrees Fahrenheit and some snow on the ground. After we performed the initial zero at 100 yards we ran the scope through the initial box test of which it did very well printing rounds at each of the corners and the fifth group coming right back on top of the first. This test has really become more of a formality these days as even the low end scopes will tend to do well on this test when the scopes are new out of the box. Over time the cheap scopes can loosen up as the internal gears wear quickly due to inferior materials, such as nylon, being used. We do not expect that to happen with this SIII scope as it is made with higher quality materials.

The next test we performed was the MOA adjustment range measuring test. We fired our initial group which measured just a tad over .5 MOA and then dialed in 20 MOA of left adjustment and fired the second group. We then dialed in the 20 MOA of right adjustment back into the scope and fired a third group, which was right on top of the first, a further indication of good repeatability of the adjustments. When we measured the distance between the two groups from center to center it measure 21.15″. At 100 yards 20 MOA equals 20.94″ which means there was 1.00% of error in the adjustment size. Due to the possibility of error being introduced due to group sizes, we consider 5% to be a passing grade and 3% to be very good and what we like to see. So this scope performed great with only 1% error.

The optics on the scope are very sharp and bright which was no surprise since the scope is a part of the SIII line of scopes. There was good contrast and the image maintained is sharpness all the way to the edges. The objective lens is only 42mm, but the lens coatings are good quality so the light gathering capability appears to be good for what the scope is. With a fixed 4.2mm exit pupil size, it is also easy to get a full scope picture without scope shadow. We sometimes forget how nice a large exit pupil is on a scope when we get used to the sub 3mm exit pupil sizes found on high magnification scopes.

The reticle is a modified mildot reticle (See the picture above) that has the traditional army sized mildots measuring .2 mil in diameter. The modified part of the name refers to small hash marks at each half mil measurement. The reticle is clean and easy to use and effective. It is a nice match to the rest of the scope and on a whole the optical capability of the scope is solid with accurate adjustments.

The final tests that we normally perform on a scope is to check for reticle drift when cycling through the zoom power and also when adjusting the parrallax focus through the entire range. Because this scope is a fixed powered scope, that immediately eliminated one of the potential error points, leaving only the possibility of reticle drift when using the parallax adjustment. We mounted the bore sighting grid to the muzzle and then used the adjustments to align the reticle with one of the intersection points on the grid. We then cycled through the entire parallax range while observing for any movement in the reticle. We can report that from 50yards to infinity, the reticle showed no movement at all. Unfortunately from 50 down to 10 yards, we did observe some shift. Most scopes do not have a parallax adjustment that goes down that close, and we are not sure why Sightron decided to go to that extreme on this scope. Down on those bottom ranges, especially below 25 yards, we did notice the reticle wandering a bit. If you plan to use this scope as a 10 meter air rifle scope, then it may be a concern, else, it should be good to go if using it for its intended purpose as a longer range tactical scope.

Overall, we can state that yes, we still like fixed power scopes. It may seem old school, but with the simplicity of operation and the increased durability due to less parts to fail, we find that there is still some value and use for a good fixed power tactical scope. The SIII 10x42mm is a solid offering, it has very good optics, the mechanical adjustments are spot on, and the over all quality is nice. The light weight and smaller than average size are good features on a field rifle and that is what we like about this scope. It seems to make a very good scope to use on a rifle that is going to see a good amount of field use, one that would be drug through the weeds, carried long distances, and then expected to perform. It is not a feature laden scope and it is not without its faults either. We would probably prefer to see a slow focus eyepiece for increased durability and have the parallax adjust start at about 50 yards for better precision and accuracy. A side focus may still be preferred as well, but the rear focus control works well, so we wont hold that against it. Of course, a windage knob that counts up both directions is another little thing we would like to see changed. But with those things said, we still liked it and are glad there are still some fixed power scopes available to use, and we still like them.

Sniper Central

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