U.S. Optics ST-6 Scope Review
May 12, 2011

U.S. Optics ST-6 Scope Review

Although today's economy may be tough, there are still people wanting not just good, but great, high quality, rugged and dependable optics (scopes).  Several big name optics manufacturers out there are trying to cater to this crowd, and honestly they do put out some good tactical products. However, they don't seem to be providing a military grade optic (scope).  Immediately you're probably thinking I'm nuts, and you know that big name scopes are used in the military today, but bear with me.  When I say military grade, my reference is to something above just high quality tactical capability, but something that can withstand extreme conditions. 

There is one company that has targeted this market, and that company is U.S. Optics.  When you visit their website, they are pretty clear about their products by having a slogan "Engineered for Extreme Performance".  U.S. Optics is an American company and they claim to be "building one of the most durable rifle scopes in the industry today".  They also claim to "offer more options and accessories than any other rifle scope manufacturer", and each scope is basically custom built to your specifications.  While looking online at the U.S. Optic products, I got the impression that they do offer many options, and the appearance of their scope seemed rugged.  The next thing I looked at online were prices on a couple of the their scopes, and clearly these scopes must have high end optics and be of great quality to support their price tags.

While working on a review for the Ruger Gunsite Scout Rifle, I came across the opportunity to review one of the U.S. Optics scopes and jumped at the chance.  I was able to obtain the U.S. Optics ST-6 fixed 6X power scope, and I reviewed this scope while installed on the Ruger Gunsite rifle.  The base price for this scope at the U.S. Optics website is $970, and there are not many other retailers that carry this scope. This means you are probably going to have to pay about that amount.

The following text in colored italics was taken directly from the U.S. Optics website or their Product Catalog on 4/27/11 and gives an overview and the specifications for the ST-6 scope.  The , and are my way to keep up with details that I have covered in this review with either photos, commentary, or both.  I may also add commentary after these marks or as necessary to explain some items if needed.


  • The ST-Series of rifle scopes represents U.S. Optics' offering of an affordable, fixed  magnification, long range riflescope.
  • Extreme durability, unmatched resolution and compact simplistic design make this scope an obvious choice for any marksman.


  • Model: ST-6
  • Power: 6X
  • Weight: 1.40 pounds
  • Eye Relief: 3"
  • Eyepiece: Rapid Focus
  • Eyepiece Housing: Low Profile
  • Eyepiece Covers: U.S.O. Flip-up
  • Tube: 30mm
  • Color: Matte Black Type III Hard Coat Anodized
  • Elevation Knob: U.S.#1 1/2 MOA
  • Windage Knob: U.S.#1 1/2 MOA
  • Reticle: JNG MOA
  • Parallax: Fixed
  • Objective: 28mm
  • Objective Cover: U.S.O. Flip-up
  • Field of View: 25 feet at 100 yards
  • MOA Adjustments: 120+
  • Waterproof: 33 ft.
  • Dustproof: Yes
  • Shockproof: Yes, 50 BMG capable
  • Nitrogen Filled: Yes
  • Multi-Coated Optics: Yes, all glass surfaces have a proprietary multi-coating

What's In the Box

When the scope arrived, it was packaged in a very simple box, and there was an accompanying manila envelope with instructions and literature.  I don't mind simple boxes because it is what's inside that counts.  It seem the more you spend on a scope, the more plain the box.  Conversely, the less you spend, the fancier the box.

Figure 1
U.S. Optics ST-6 Scope Review

The end of the box had a label with all the significant information.

Figure 2
U.S. Optics ST-6 Scope Review

The scope was wrapped in a thick plastic bag with layers of bubble wrap on top and bottom.

Figure 3
U.S. Optics ST-6 Scope Review

The photo below shows the configuration of the scope when removed from the package.  It was in perfect condition with no scratches or blemishes.  Actually on page 2 of the Warranty, it states that "the scope is checked carefully by at least two people and no new scope is allowed to leave the plant with scratches or dust", and I believe it.

Figure 4
U.S. Optics ST-6 Scope Review

The envelope contained a matching serial number to the scope.

Figure 5
U.S. Optics ST-6 Scope Review

Inside the envelope was a set of product pamphlets and U.S. Optics stickers as shown below.

Figure 6
U.S. Optics ST-6 Scope Review

Also in the envelope was my Invoice (not shown), Operating Instructions, Instructions for Telescopic Sight Erector Centering, Lens Cleaning, and the Warranty. U.S. Optics also provides videos at these links covering Erector Centering, Scope Mounting and Scope Lens Cleaning.

Figure 7
U.S. Optics ST-6 Scope Review

My first impression of the scope was that it was "shear raw ruggedness" and it gave me a "utilitarian" feel.  The 30mm tube, large eyepiece and large turrets also gave me the impression of "beefy".  When holding it, my impression of sturdiness continued to grow due to the mass of the scope.

Figure 8
U.S. Optics ST-6 Scope Review


Scope body, eye piece, objective housing and any and all other body parts are made with 6061-T6 aircraft aluminum and are then coated with a matte black type III hard anodizing.

Figure 9
U.S. Optics ST-6 Scope Review

The scope with covers measured 11.32" in length.  There was 1.13" of 30mm tube exposed forward of the turret housing and 1.98" rear of the turret housing.

Figure 10 - Top Side
U.S. Optics ST-6 Scope Review

Figure 11 - Right Side
U.S. Optics ST-6 Scope Review

The bottom of the scope is marked with the serial number of the scope and the manufacturers name.

Figure 12 - Bottom Side
U.S. Optics ST-6 Scope Review

The large cap shown below on the left side of the scope is where you would install the green or red reticle lighting 11 position rheostat.  I believe the other small cap is where they fill the tube with nitrogen to displace any air and prevent fogging.

Figure 13 - Left Side
U.S. Optics ST-6 Scope Review

The scope comes with U.S. Optics custom flip-up covers.  You will need to remove the cover on the eyepiece end to adjust the focus on the scope for your eyes and then reinstall the cover so it is clocked to flip up.

   Figure 14 - Eyepiece End                                      Figure 15 - Objective End
U.S. Optics ST-6 Scope Review   U.S. Optics ST-6 Scope Review

Figure 16 - Eyepiece End                                      Figure 17 - Objective End
U.S. Optics ST-6 Scope Review   U.S. Optics ST-6 Scope Review

The next couple of photos show the scope with the turret covers removed and the flip-up covers in the up positions.  This is the first look at the large 24 MOA turrets. The turret materials consist of stainless, brass, 4130 alloy steel, and the ball detents are tungsten carbide with a stainless steel jacket. The scope also includes duel elevation and windage rebound springs.

Figure 18
U.S. Optics ST-6 Scope Review

Figure 19
U.S. Optics ST-6 Scope Review

The eyepiece measures about 1.71" in diameter and has a total length of 3.58".  The rapid focus eyepiece turns about 1.4 total turns for the full range of adjustment.  You can also see a slight greenish tint on the lens that indicates some type of coated optics.

Figure 20                                                                    Figure 21                        
U.S. Optics ST-6 Scope Review  U.S. Optics ST-6 Scope Review

The objective end measures about 1.37" in diameter and has a length of 1.97".  The objective lens seems to have some type of coating also.  I have not been able to get any details on the coatings other than all class surface have a proprietary multi-coating.

                                         Figure 22                                                                    Figure 23
U.S. Optics ST-6 Scope Review   U.S. Optics ST-6 Scope Review

The windage and elevation knobs are the U.S. #1 knobs. They have 48 clicks per revolution which gives 24 MOA of travel per revolution in 1/2 MOA clicks. U.S. #1 knobs are the standard option on this scope.  When my scope arrived, the MOA hash marks on the turret cap didn't line up perfectly with the index mark on the turret body. I was able to loosen the top screw and rotate the cap without adjusting the zero on the scope.

Figure 24
U.S. Optics ST-6 Scope Review

The photo below shows the turret caps after I made the adjustment.  For the elevation turret, rotating the turret cap counterclockwise (in the direction of increasing numbers of MOA) moves the point of impact up.  For the windage turret, rotate the turret cap in the increasing numbered direction 1R, 2R, 3R, etc. to move the point of impact to the right or 1L, 2L, 3L, etc. to the left.

Figure 25
U.S. Optics ST-6 Scope Review

Using a 3/32" Allan wrench, I removed the screw holding the turret cap in place.  The screw actually pushes on a large black washer that presses on the cap.

Figure 26
U.S. Optics ST-6 Scope Review

Next I was able to lift the turret cap off the actual rotating turret (brass part shown below).

Figure 27
U.S. Optics ST-6 Scope Review

I did the same for the elevation turret.  The photo below shows two O-rings that seal the turret cap to prevent water from getting inside the turret workings.  The bottom O-ring is covered with grease and the turret cap slides against this O-ring when making an adjustment.  The top O-ring does not slide against the turret cap and no grease is required.  Also, I believe you should not let grease get on the tapered surface because it is this surface in contact with the mating tapered surface on the cap that creates friction when you tighten the screw and ensures the turret and cap always rotate together.

Figure 28
U.S. Optics ST-6 Scope Review

The turret body includes reference marks so you can relocate your zero point in the event you loose it during adjustment operations.

Figure 29
U.S. Optics ST-6 Scope Review

The turret covers are aluminum and measure 1.35" tall and about 1.38" in diameter at the knurled area.

Figure 30
U.S. Optics ST-6 Scope Review

Figure 31
U.S. Optics ST-6 Scope Review

The scope, turret covers and flip-up covers weighed in at 1.42 pounds.  The flip-up covers alone weighed 0.05 pounds, so the scope and turret covers (I consider them as part of the scope) weighed in at 1.37 pounds which is in line with the 1.40 pounds per the specifications.

                  Figure 32                                                           Figure 33
U.S. Optics ST-6 Scope Review   U.S. Optics ST-6 Scope Review

JNG MOA Reticle

The reticle is a JNG MOA reticle.  The photo below is taken looking at a wall, and the two dots were some type of glare off the ceiling lights.  Also, I was having difficulty getting the reticle in focus with the camera in many of the next photos.  This may be due to the reticle being in the first focal plane for this scope.  When you look through the scope with the eyepiece focused, the reticle appeared very sharp and clear.

Figure 34 - JNG MOA Reticle
U.S. Optics ST-6 Scope Review 

The next photo shows a close up view of the reticle.  This reticle has fine crosshairs that are marked in 2 MOA increments from 24 MOA down to 36 MOA up and 36 MOA left and right.  It also has a 36 MOA diameter 2 MOA thick aiming circle.

Figure 35 - JNG MOA Reticle
U.S. Optics ST-6 Scope Review

The figure below is also found at the U.S. Optics website and shows additional details about the reticle.  The more I used this scope and evaluated the reticle, the more I liked this style of reticle.  The aiming circle seems great for close quarters and the reticle gives you the ability to correct you shot without having to adjust your turrets and also doesn't take up too much of your field of view.

Figure 36 - JNG MOA Reticle
U.S. Optics ST-6 Scope Review

Before I start evaluating the reticle and scope adjustment features, I want to be clear on the definition of MOA.  MOA stands for Minute of Arc or Minute of Angle and one MOA at 100 yards is equal to 1.047" on paper.  I will use this 1.047" factor to calculate scales and distances to evaluate the reticle and elevation/windage MOA markings.

Verifying Reticle Scale

In my first evaluation, I wanted to determine if the reticle MOA scale was accurate.  To do this, I setup a target of known diameter (27") at 50 yards and mounted the scope on a tripod, and then I placed a camera behind the tripod.

Figure 37
U.S. Optics ST-6 Scope Review

The photo below shows the cross hairs on the center of the target.  Each ring on the target is 1" in width, but the center circle adds another inch, so the total diameter of the large yellow circle is 17".  Since my target is 2x larger at 50 yards than that at 100 yards, this 17" diameter is equal to 34" if seen from 100 yards.  Since I want units of MOA, this 34" circle is 32.5 (34/1.047) MOA across.  What all this means is that if the reticle is to scale, the edges of the large diameter yellow circle should be falling at about 16.25 MOA on the scope reticle.  Based on the view below, I would say that they are about as close is it could get.  Since this mid range point matches, I believe the rest of the reticle MOA markings will match also.

Figure 38
U.S. Optics ST-6 Scope Review

Verifying Tracking

Next I wanted to evaluate how the position of the reticle tracks into each quadrant from zero and then returns back to zero.  To do this, I mounted the U.S. Optics ST-6 on my Ruger SR-22 with a green laser mounted in front as shown below.

Figure 39
U.S. Optics ST-6 Scope Review

I adjusted the scope reticle to be on target with the laser projection at 71.6 feet (23.9 yards).  This distance allowed me to be able to make MOA adjustments such that 1 MOA (1.047" at 100 yards) equals 1/4" on the target.  Since the center of the aiming circles are exactly 6" apart, I could evaluate a 24 MOA change in both elevation and windage.

Figure 40
U.S. Optics ST-6 Scope Review

By re-centering the laser (bullet impact point) on the center target, I was able to see the shift in the reticle position based on my 24 MOA elevation and windage adjustments.  If the reticle was tracking properly with the MOA adjustments on the turrets, a 24 MOA adjustment in each would cause the reticle center to land on the center of the aiming circles in each corner of the target.  The photos below are proof that the turret MOA adjustments are correct.  Keep in mind that taking these photos was extremely difficult and any out of focus or slight differences are probably due to my bifocal eyes and my camera abilities.  When looking through the scope with the eye, the images were sharp and clear.

Figure 41                                                                Figure 42
U.S. Optics ST-6 Scope Review   U.S. Optics ST-6 Scope Review

Figure 43                                                                Figure 44
U.S. Optics ST-6 Scope Review   U.S. Optics ST-6 Scope Review

After making all these adjustments, I returned the elevation and windage turrets back to the zeroed position and checked to see if the reticle center lined up with the laser. The photo below shows the results.  I would say this is a very good return to zero.

Figure 45
U.S. Optics ST-6 Scope Review

Optics Brightness and Clarity

For my last backyard evaluation, I wanted to compare the optics against a similar quality scope.  The closest quality scope I had on hand was a Zeiss Conquest 4.5-14x50mm Scope.  I set the Zeiss to the 6X power so I was comparing a similar magnification range.  The Zeiss was clearly brighter, but this was due to the larger objective (50mm) on the Zeiss as compared to the U.S. Optics ST-6 (28mm).  At 6X power, the Zeiss had a twilight factor (exit pupil diameter) of 8.3mm (50/6) as compared to the ST-6 at 4.7mm (28/6).  I figured the Zeiss would be brighter, but my real point in comparing these two scopes was to make an evaluation of clarity and crispness of the scope.  To do this, I studied the detailed features of the multi-dot target shown above throughout the entire field of view of the scopes.  Overall, I believe the Zeiss did have slightly better sharpness, but the U.S. Optics was a very close second.  I then compared the scope to several other scopes costing a fraction of the price and there was no doubt that the U.S. Optics scope was brighter and had better image quality.  Because doing an eyeball comparison is subject to interpretation, I recommend you checking one out yourself.

Figure 46
U.S. Optics ST-6 Scope Review

Range Test

My final test of the scope was at the range 100 yard range (actually 105 at this range) on the Ruger Gunsite Scout Rifle.  I shot about 5 boxes of ammunition through the rifle over a period of about 2 hours (4 boxes shown below).  I did an initial sighting in of the scope and then started shooting 5 shot groups.  Throughout that time, I enjoyed the clear, crisp and bright image through the scope.  One thing is clear, I am becoming a big fan of the JNG MOA Reticle.

Figure 47
U.S. Optics ST-6 Scope Review


Based on my examination of the U.S. Optics ST-6 scope, I believe it would be extremely durable.  If you have a chance to examine one for yourself, I think you will come to the same opinion.  While looking for more information on the durability of U.S. Optics scopes on the web, I came across a YouTube video that gives you a good idea on the durability of the scope.  In the video, L&M Outdoors shows shooting a group of shots, removing the scope, tossing it in the air and letting it hit the ground 4 different times, remounting the scope, and shooting another group.  The scope took this abuse and maintained its zero.  Click here to see this video on YouTube.


U.S. Optics offers a Limited Lifetime Warranty to cover any issues associated with the scope that may be related to defective materials or workmanship.  This warranty is to the original retail purchaser and they must return the scope in the original packaging with the original purchase receipt.  A copy of the Warranty certificate must also be presented.  The key thing with any warranty is to read the fine print and prepare yourself for the chances that there could be a problem in the future.


Bottom Line:

I was very pleased to get an opportunity to review the U.S. Optics ST-6 6X Scope.  There is no doubt that U.S. Optics is putting out some rugged and quality scopes and this ST-6 review should give you an idea on what you could expect from any of the other U.S. Optics products.  The reticle and elevation/windage MOA markings were scaled properly.  The elevation, windage and return to zero tracking was good.  The elevation and windage turrets adjusted with positive clicks and no looseness.  The fit and finish of all features of the scope were good.  Since I didn't have a 28mm objective scope to compare, I was not able to get any good comparative data on the brightness of the scope.  I did compare the brightness and image quality to some other scope costing a fraction of U.S. Optics and found the ST-6 was clearly superior.  The only thing I found negative while doing the review was the difficulty in getting details on this scope from the U.S. Optics website.  Considering the price of this scope, I wish U.S. Optics would have a section at their website that talks a little more about optics portion of the scope, specifically the coatings.  If you are in the market for a high quality and extremely durable scope, I recommend you taking a close look at the products offered by U.S. Optics.

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