Review: U.S. Optics SR-8C 1-8x27mm Scope

BigJimFish's Review of the U.S. Optics SR-8C 1-8x27mm Scope with C2 Reticle

Table of Contents:

- Background
- Unboxing and Physical Description
- Reticle
- Comparative Optical Evaluation
- Illumination Evaluation
- Speed Testing and Discussion of Contributing Factors
- Mechanical Testing and Turret Discussion
- Summary and Conclusion

Background:

I first spoke with U.S. Optics five years ago when I was just starting to write reviews. I had not been writing on optics long before I became dissatisfied with existing reticle options, particularly in the variable power low magnification class of scopes, and I contacted them regarding custom reticle design. This was the start of something, in reticle design, that would become a rabbit hole for me. It was also the start of a productive relationship with the staff at USO. They have selflessly given of their time and expertise helping me to come to a better understanding of the workings of optical systems. Expertise they may have in abundance, but their time is a scarce commodity and I appreciate the help, especially that which was given when I was just some yahoo and not a credentialed member of the press.

USO was started in a garage in 1990 by John Williams, an entrepreneurial engineer, and his son. They acquired some equipment and staff gained from Rockwell Scientific following an abrupt reduction in military demand for the products of that company at the end of the cold war era. They were willing to take this significant risk of time and capital because they saw a lack of products in the rifle scope market that were both rugged and designed with the feature sets that a serious precision rifle shooter needs.

The unique approach to the problem of feature sets that USO took was to allow the customer to mix and match whatever he or she wants. Though USO recently began to offer a few stock models (simply the most popular combinations of feature sets), they are alone in that the customer may still build a truly custom scope though them by selecting knobs, reticle, tube size, illumination, and even engraving. This focus on customizability has led USO to have one of the largest stables of reticle designs in the industry as well as a variety of different adjustment knobs and illumination colors. These options are not repetitive or meaningless: they are designed by shooters and many have been trend starters. The best example of this is probably the EREK knob that started the trend towards zero stops in elevation knobs. They have also been instrumental in the trends towards using the same units for the adjustments and reticle and have also made significant contributions to various aspects of reticle design.

Leaving an introduction of USO without talking about customer service would be remiss of me. USO is a small operation. It comprises less than thirty individuals and is housed in one building. Because of this scale they have control of, and accountability for, product quality as well as selection and education of personnel that is unusual. As a small business owner I can appreciate the benefits of a smaller, easier to manage, organization. It is this kind of accountability that makes it unlikely that you will need to send a scope back. Nevertheless, scopes contain wear components and, if you use them regularly, eventually you will need these wear components, such as o-rings, serviced. Not only is USO generous when it comes to this sort of thing, but they are also informative and easy to work with. When you call them up it won’t be like the USPS, where you find out your package is somewhere in the ether and they are not sure where or when you will get it back. Instead, you will actually find out what is going on. I have even heard of loaner scopes being sent to folks who had a match during the time their scope was being serviced. What I am saying is that, with USO, you can expect to be treated fairly, kept informed, and ultimately satisfied, even in the unlikely event that your scope should have an issue.

Unboxing and Physical Description:

USO’s packaging has achieved something resembling cult status. It is so simple and perfunctory that it borders on the absurd. USO scopes come in a plain white box with a label affixed to one end bearing the scope’s details and wrapped once around the middle with a piece of packaging tape bearing U.S. Optics name. Despite their simplicity, these boxes are somewhat coveted and easily add $100 to the used sale prices of USO scopes.


U.S. Optics SR-8C unboxing

Inside of the unique box, I found the SR-8C wrapped in bubble wrap and a thick plastic bag. I also found USO logo flip caps as well as a manila envelope labeled with the scope’s details and containing the manual paperwork. This scope example probably contained one of the last old style manuals to be produced. I have noted that the USO website contains PDFs of new product line specific (and much more comprehensive) manuals. That is a great improvement as the old manuals were not a cohesive whole, but rather, a few sets of loose instructions. The new instructions booklets are far more complete, contain more and better images, and are organized into a format that is easier for the user to understand.

The SR-8C itself is unusual in appearance. It is, relatively speaking, long, at 12in; thin, at 30mm; and, not surprisingly, on the heavy side, at 34oz. The unusualness in appearance stems from having a much longer section of tube behind the adjustments than in front of them. This is a design feature that I also remember being present in the first incarnation of the Premier Reticles 1-8x that was never to be. I expect this aspect ratio stems from the fact that it is this section of the tube that holds the erector mechanism. This mechanism, which holds the reticle and also the set of lenses whose movement is controlled by the power ring, is responsible for changes in magnification. It makes sense that a massive 1-8x power range might dictate a longer erector tube to allow for more movement. In any case, the result is a unique appearance that is readily identifiable. I do not find the effect unpleasant. The flared objective, holding a larger than most 27mm lens, probably helps with this. Instead, I find the appearance kind of intriguing.

Many of the other features of the SR-8C will be familiar to the user. The SR-8C features the digital illumination control module debuted a few years ago by USO. This unit is much more rugged and water resistant than the previous analog unit. It also close to doubles battery life. As shown in the close-up photo of the turret area later in this review, the brains of this unit are user removable along with the battery by unscrewing its housing. This allows for easy repair, if necessary, and the unit is small enough that a soldier who doesn’t trust electronics could conceivably bring a spare. The eyepiece on the SR-8C is the now familiar USO low profile eyepiece with a euro style diopter and a large, knurled, 270 degree throw power ring.

The mount pictured in the featured and final images is the American Rifle Company M10 QD-L that I reviewed earlier this year.

Reticle:


U.S. Optics SR-8C with C2 reticle at 8x focused on a tree line at 100 yards. Haze in the bottom left quadrant is caused by the photography set up and not the optic.

At the time of this writing, four reticles are made for the SR-8C. The most common one, and the one offered off the shelf through distributors, is the 8C mil. This reticle is identical to the no longer offered C2 reticle that my example has, except that the circle feature is absent in the 8C, the cross hair is much finer and both the x and y axis of the cross hair extend to the stadia of the reticle. In practice, four things stood out to me about the reticle. The first thing I noticed is that the circle feature is totally unnecessary for close quarters use. The illumination on this scope is the dominant close quarters feature. The circle is superfluous and I am happy to see it go with the 8C update. The second thing I noticed is that, at high power, the center lines are thicker than I would like. This has also been remedied with the 8C. Overly thick reticles are a curse of FFP scopes and is especially pronounced in this 8x magnification ratio model. Because the reticle is magnified along with the target, it is difficult to find a line thickness that is thick enough to be seen at low power but doesn’t look like a 2×4 at high power. The solution to this is to have more than one line thickness. The center should be stepped down, but that was not done in this case and, therefore, it is difficult to aim precisely at high power for purposes such as establishing a 100yd zero. The third thing that I noticed was that the reticle’s graduations, which have no labels and utilize tick marks of differing lengths for odd and even mils, is not intuitive. For a second I thought the increments were twice as wide as they should be because I naturally assumed the longer lines represented 1 mil divisions with the shorter lines interspersing them at .5 mil increments. This is not the case on this reticle. It is one of the few reticles so graduated that I am aware of. Lastly, a classic mil hash reticle, such as this one, works best when paired with a target style adjustment knob. The zeroing knobs that the example I have is paired with do not match up well with the mil hash reticle for long range shooting. In the future I understand that USO is going to offer a mini EREK knob in this model. That will match up very nicely with their classic mil hash reticle choices.

The first of the custom shop reticles, and my favorite for this optic by a large margin, is the RWF 3GUN. This reticle, like many in the USO catalog, was designed by a third party who believed enough in his design to put up the cash for ten optics. The reticle mates better than any of the others with the low profile knobs on the SR-8C because it features a caliber-specific BDC section surrounding the six o’clock crosshair. This section is calibrated for MK262 ammo and has drops and windage out to 800yds from a 100yd zero. All four quadrants of the crosshairs are labeled in mils with graduations every half mil. Strangely, the even number mil hash marks are shorter than the odd number hash marks with the 1/2 mil hash marks being shorter still. I found this needlessly confusing and the only outright bad choice in this reticle design. The even and odd hashes should be the same length. The RWF 3GUN reticle has one more innovative feature on it that I proposed some five years ago to several optics makers but no one picked up. It must not have been that bad an idea because it appears that Ron has independently come up with it and used it in his design. That feature is to offset the central close quarters aiming feature, in this case the dot, below the 100yd zero line so that it better lines up with actual close quarters targets.


RWF 3GUN reticle for the USO SR-8C

The SR-8C is also offered with a Horus reticle. Oddly, this reticle is graduated in MOA. I don’t like MOAs because the math is a mess. Most people think of an MOA as an inch at 100 yards, but it is not. That angular measurement is referred to as IPHY and has nice easy calculations with multipliers of 100 associated with it. The MOA does not have easy calculations because it is 1.047? at 100 yards rather than 1.000?. In the most common equation used, this causes you to multiply by 95.5 instead of 100. Other than the fact it is dimensioned with a unit I have no use for, the Horus reticle looks about like other Horus reticles except that: the upper quadrant also houses a 90 degree MOA scale, there appears to be a set of caliber-specific windage lines, there are caliber-specific indicator marks for drop, and, lastly, there are two circle features. The design is an unmitigated and virtually indecipherable mess. You start out with a scale unit, in MOA, that no one in their right mind would use because the math is a mess. You go on to stick a secondary scale right in the middle of the upper half, where most folks like to have a little bit of clear space to get an unimpeded look at the target. Next, throw in some circles because circles are fast and two is better than one. Do this despite the fact that the optic has projected dot illumination and doesn’t need even one circle to add any speed. Lastly, superimpose caliber-specific bullet drop elements right on top of your already cramped MOA scale. Don’t scallop anything, break any elements, or do anything to make things any clearer or mitigate the look of one type of design being dropped right on another. This is the least artful, most cobbled together, abomination of a reticle design that I have ever witnessed. I also expect that it is expensive but I’m not going to bother asking and neither should you. You should choose a different reticle and Horus should spend more time working on designs and less suing everyone for stealing their clearly brilliant ideas.


Horus H-130 reticle for the USO SR-8C. It’s like Turducken, except not good.

The last reticle offered is the JNG Mil. I’m not going to go into this one in any depth because it is functionally so similar to the standard 8C reticle that I would not see any reason to pay extra for the custom shop and wait 16 weeks over going with the standard 8C. Bottom line, It is a mil-hash reticle that is a little thicker than the 8C and has a broken circle feature.

Comparative Optical Evaluation:

Over the years I have used a wide variety of USO scopes including the SN-4S 1-4×22, LR-17, ER-25, and ST-10. All of the examples I have used had good to excellent clarity. This SR-8C is no exception. In my testing, it well exceeded the Bushnell SMRS but fell short of the March and Leupold offerings. In contrast to most of the other scopes tested, the color rendition on this USO was on the cool side of the spectrum. It seemed to prefer browns to greens and yellows.

Though the USO has good clarity, it is a quirky optical platform with a number of notable aberrations that I did not notice at SHOT Show, but that became apparent when I had a good long time to sit with it at the bench. These aberrations include curvature of field, pincushion distortion, and eyebox, but the effect they have at low and high power differs, so I will discuss each situation separately.

The most notable distortion at high power is the curvature of field. This shows up around 6x and becomes more noticeable the higher the magnification. Curvature of field is something of a misnamed aberration as it does not make things appear bent, but rather, out of focus. This effect stems from the fact that lenses are usually round, not parabolic, and therefore they do not actually focus all light at a single point. This results in a situation wherein your eye cannot be located at any single place and have the whole image in focus. With the SR-8C, as you move your eye around in what feels like the smallest eyebox in the test line up, you notice different parts of the image coming into sharpest focus. All parts of the field of view can be brought into focus but this cannot be accomplished simultaneously. Each part of the field will only be in focus when your head is in a particular position and that position is different for different parts of the field. Though some pincushion distortion can also be noted at 8x if you specifically look for it, it is really only the curvature of field that is problematic. This aberration is also somewhat unexpected as the USO has the smallest field of view of the 1-8x scopes and it should therefore be easier to avoid this problem in the design.


The exaggerated effect of pincushion distortion on a grid

At 1x the curvature of field is much less apparent. Sitting at the bench, the image appears edge to edge clear. Similarly, you also only notice a slightly greater pincushion distortion in the SR-8C than in the other 1-8x scopes at the bench. When in dynamic use though, users had the feeling they were looking through a straw, or as one described it, an old time telescope. I think that this impression was caused by some combination of a slight curvature of field coupled with a small field of view, tight eyebox, and magnitude of pincushion distortion greater than the other comparison 1-8x scopes. The final effect was that the user felt like the image was kind of cramped and distorted.

Overall, the optical design of the SR-8C does not appear polished, but rather quirky and a little off. The compromises made to achieve the massive 1-8x ratio are apparent to the user and they distract from the scope’s functionality.


USO SR-8C and comparison optics focused on a tree line at 100 yards. Haze in the bottom left quadrant on several optics is caused by the photography set up and not the optics.

Illumination Evaluation:

Three years ago when I first started to arrange for this big 1-8x shootout, three scopes were originally slated. These were the S&B, Premier Reticles, and Leupold. The first two of these featured beam splitter illumination technology yielding what is essentially red dot illumination. Not only would getting together this review take an extra two years to accomplish but, in the end, despite containing four 1-8x scopes, it would feature only one of the original three scopes, the Leupold, and would also only have only one scope featuring beam splitter illumination. The USO SR-8C is the optic featuring that illumination technology.

Beam splitter illumination is the most expensive and difficult to manufacture technology in a magnified optic. This technology is commonly used in the simple red dot sights that exist, but it can be adapted to magnified optics with some difficulty. With this illumination technology, the illuminated figure, in all extant designs a dot, is merely projected between the user and the reticle by means of a mirror and is not any part of the reticle itself. In fact, the projected figure is projected at infinity and does not focus with the rest of the optical design. Lining up the projected element with the rest of the reticle is a challenge for this technology and makes the cost quite high. Despite this and other difficult and costly trade offs, beam splitter technology offers some compensatory enticements. These are that, because it works independently from the etched reticle, it can be used in a FFP optic, it is daytime bright, it is battery efficient, it has no down range signature, and it can be easily paired with reflected illumination technology in a scope to allow for dual mode illumination.

This scope does not currently feature dual mode technology, but USO has bandied about doing so in the future. I expect that the manufacturing hurdle to overcome in adding dual mode illumination is that it will probably require a new illumination control module. It was not long ago that USO updated their illumination systems with a new digital illumination module. This scope has that unit. It is easy to disassemble, more durable, offers high pressure water resistance, has field replaceable electronics, doubles battery life, shuts off after an hour when left on, and returns to the previous setting when turned off. In short, it is better than the previous unit in all ways.

It is a shame that, after all these years, only of the 1-8x scopes reviewed included beam splitter dot illumination. This is clearly the most desired illumination technology and, paired with a dual mode system, would give up absolutely nothing to any other tech. It is not a pity for USO though. Their SR-8C has this type of illumination and so beats all others hands down in that arena. I hope that things will come together for the dual mode illumination in the future as well because that would aid in low light long range shooting. I say this while also freely admitting that with any of these 1-8x scopes, given their small objectives, low light long range shooting is probably optimistic thinking regardless of the illumination system.


U.S. Optics SR-8C with C2 reticle and comparison optics at 1x and maximum illumination. Target at 25 yards.

Speed Testing and Discussion of Contributing Factors:


All of the scopes to be compared in the speed testing

Over the course of the last couple of reviews, I have had the opportunity to evaluate, in cooperation with eight or nine different testers, some fourteen different optics, with a 1x setting, engaging close quarters targets. For this I use an air-soft AR and pie pans: I’m not made of money. It’s a lot of fun and you can go though thousands of rounds for the cost of fast food dinner. What I have found after doing all of this testing is that what counts for close quarters is not exactly what you would expect. Here is my summary of the major factors and what part they play:

1) Optical Design: Having a distortion-free, flat field of view at 1x is, by far, the most important factor to speed. Pincushion distortion, barrel distortion, or curvature of field throws off your ability to merge the data coming in from your left and right eyes into a single image. The result is slow and a little disorienting. This disorienting effect is not noticeable when you are focused on a stationary target, but as you move across the field of fire, having the objects viewed through the optic bend as the field of view moves across them is very hard to deal with. The SR-8C did not score well when it came to the effect of optical design on close quarters speed. The combination of curvature of field with pincushion distortion and a small field of view left the testers feeling like they were looking down a straw. It was the lowest ranking scope tested in this regard.

2) Reticle: The reticle is a little more subjective. Not every tester has always agreed. However, in general, an open field of view with a few thick objects in just the center is the desired combination. Crosshairs are generally disliked. The C2 reticle that I used, while appearing thick at 8x, becomes quite thin at 1x and therefore does not interfere with the function of the illumination. When you have illumination like the SR-8C, all you need from the reticle for good close quarters performance is for it to stay out of the way. This reticle accomplishes that.

3) Illumination: Having a daytime bright dot for an illumination system can eclipse reticle design in importance for close quarters performance, provided the reticle can just stay out of the way. That was certainly the case for the SR-8C. There is no competing with beam splitter tech and daytime bright red dots.

4) Eyebox: It should come as no surprise that having more freedom of motion while still getting a picture is good for speed. However, what I have found is that, within reason, this factor plays less a part than you might think. It is true a tiny eyebox can make an optic slow, but most scopes have enough leeway that it is not a big factor. The eyebox of the SR-8C felt the tightest in the test group and that fact was noted by almost all testers. Low margin for head movement certainly had a detrimental effect on the scope’s overall speed.

The USO SR-8C was the most operatic of all scopes in the lineup when it came to speed testing. It was the only optic to be rated fastest by one reviewer and slowest by another. This difference of opinion came down to having the best illumination, smallest eyebox, and most distorted optics. Depending the magnitude of the effect of each of these factors on a given individual, this scope could land anywhere on the comparative speed scale. On average though, it landed in the bottom half.

Mechanical Testing and Turret Discussion:

At the time of this writing, the SR-8C is only offered with capped zeroing turrets. As the name suggests, these are really only intended for zeroing the optic. Though it is certainly no EREK knob, this is probably not a totally fair assessment of these adjustments. Just a few years ago a turret with nice tactile clicks, clear labeling, a zero that could be repositioned, and more than 9 mils of travel was all you could ask for. Today we can ask for much more and, especially given the mil hash reticles that this optic is supplied with, the forthcoming mini EREK will be a significant edition. That aside, these will do fine in a pinch. They are very small, but by using .2 mil increments instead of .1 mil, they maintain the best in class feel U.S. Optics is known for and still manage more than 9 mils a turn. The zero reset is accomplished by loosening the two #8 torque screws on the cap and then lifting up and rotating the knob. This is not the slickest system. The adjustments get the job done, though I expected more given the reticles offered and the long range capabilities of an 8x maximum magnification.


Close up of the U.S. Optics SR-8C saddle section. The elevation turret had been disassembled as well as the illumination module.

For the adjustment testing of the USO SR-8C and other scopes being reviewed this year, I made up the new target shown below. I spend a good deal of time shooting at my local 100-yard range with scopes that are adjusted in mils. It annoyed me that I could not find a target made on a mils at 100 yards grid. I therefore made one and furthermore, made it have six bulls so that I can shoot a box and power change test on the same target. The grid on the pictured target is .1 mil at 100 yards. I will make the PDF of this target available just as soon as I can figure out a way to get the CAD program to make a PDF of the correct size. (It seems to be able to print out the correct size, but the PDF is not right. I will have to use some printer plug in.)

A box test checks for the accuracy in magnitude and independence in direction of the adjustments. To perform this test, the shooter aims at the same place when firing all shots, but moves the adjustments between groups such that a box is formed by the groups fired with the last group landing back atop the first. This box should be square and the corners (i.e. the groups) should be the correct distance from each other as dictated by the scale of the scope’s adjustments. As performed on this target, all of the groups should have the same position relative to the exes. The USO passed this test with no difficulty.

In a power change test, the rifle is fired at two different targets with one being shot at maximum magnification and the other at minimum. The targets are then compared to make sure that the scope does not shift with regard to point of aim when the power is changed. Some shift is expected with a second focal plane scope, but a front focal plane scope, such as this one, should exhibit no shift. The USO exhibits no shift.


U.S. Optics SR-8C box and power change test targets

Summary and Conclusion:

When I left SHOT Show last year, this USO was one of my favorite products. I was anxious to get some real time with it and see how it stacked up. Obviously, I am a bit disappointed. With some quality time behind the optic, and with other optics side by side, significant aberrations became apparent both by comparison and even when viewed alone. 1-8x scopes have incredibly high erector ratios and accomplishing that without noticeable sacrifices is not an easy task. It is also not an easy task to provide daytime bright illumination. This is a task most competing scopes fail at but at which the SR-8C is successfully.

Beyond the foibles with the optical platform, which are the crux of my complaint, I found some important features meshed poorly. Mil hash reticles, loved by many (though honestly, not so much by me), pair best with feature rich turrets. The ‘dial for drop, hold for wind’ usage mode is a fast and effective distance compensation method, provided the distance to the target is already known, and works best when a high clicks per revolution with zero stop elevation turret is paired with a mil hash reticle. The current incarnation of this design does not have the turrets to best accomplish this. Similarly, round specific bullet drop reticles pair well with diminutive knobs. This scope has the knobs but the reticle for this, the RWF 3GUN, is custom shop only. That reticle should be the standard with these diminutive adjustments.

I should also mention the fact that, currently, no MOA adjustment graduations are available to pair with the Horus H-130 MOA reticle. If I could think of a reason for any anyone to purchase this reticle, that would be a problem.

I expect that some of my issues will be remedied in the future and also that some new features slated will make this a much more desirable optic. The forthcoming mini EREK will pair quite well with several of the existing reticles and a new dual mode illumination control module would complete the illumination domination of the SR-8C.

Here is Your Pro and Con Breakdown:

Pros:
- Best in class illumination and the possibility of dual mode illumination in the future
- Clarity is good
- Adjustments pass the box and power change tests
- Mini EREK knob expected in the future that will offer high mils per turn and zero stop
- U.S. Optics’ excellent warranty and best in industry customer support

Cons:
- Significant curvature of field apparent at high magnifications
- Small field of view
- Curvature of field, pincushion distortion, small field of view, and small eye box all combine at 1x to give the appearance of looking though a straw
- Limited adjustments make the standard reticle less desirable
- Heavy

If you would like to comment on this article or on your own experiences with the USO SR-8C, please do so in my earlier forum post on the topic.


U.S. Optics SR-8C 1-8x27mm scope in an American Rifle Company M10 QD-L mount on a SCAR 16s