Military optics have matured quite a great deal in the 100 years since the First World War. While military optics had been used for quite some time, even before the Civil War, they did not achieve wide-ranging acceptance until the War to End All Wars was in full swing. Today’s military optics are quite different,  yet in some ways, strikingly similar to what was used a century ago. SIG SAUER recently won a major military contract for its TANGO6T scope, which just happens to be the subject of this piece.

The use of optics on small arms has become very commonplace in today’s world. In fact, it is more common to find guns with some sort of optical equipment than without. Iron sights still play an important role across the world, but today find their majority of use on sidearms. While it is always important to have an understanding of how iron sights work, the myriad of optical platforms available today is truly dizzying and quite complex.

Over the last 20 years, military optics have seen greater standardization and a streamlining of features. The dominant military optic for combat small arms has been the Trijicon ACOG in one form or another. Most of the standard ACOG sights are set to 4-power magnification and feature bullet drop compensators in the reticle. The ACOG is well known as one of the most rugged and reliable optical sights available today. It is, however, slightly antiquated in  comparison to what is currently available.

The legacy ACOG from Trijicon is an excellent scope in its range. SIG SAUER has burst into the market for military optics and is making a splash at longer ranges.


The basic features of the TANGO6T don’t immediately stand out on a spec sheet; however, in combination with each other, they deliver an incredibly effective and compact package. The scope features a 30mm main tube and a magnification range of 1 to 6 power. The reticle is a first focal plane type, meaning that the reticle itself zooms in and out with magnification, thus allowing the same firing points and range estimation ability regardless of magnification. The adjustments for windage and elevation are 0.2 MRAD, or roughly equivalent to 2cm at 100m. While this is not a spectacularly precise click value, it is certainly fast and easy.

The elevation and windage are adjustable in 0.2 MIL clicks.

The scope itself is available in both Flat Dark Earth and Black. It comes with a throw lever for fast zoom but attaching it is optional. The windage and elevation turrets are capped and feature rubber gaskets to prevent moisture or coming loose. The illumination turret can lock in place. In order to adjust illumination of the reticle, you have to lift up on the locking ring and rotate to your choice of illumination brightness. It can be locked in place by lowering the lock ring.

The TANGO6T comes with an easy-to-use throw lever for fast magnification changes.

There is a choice of five different reticles available for this scope. The reticle tested is the horseshoe dot version. It features a general bullet-drop compensating feature out to 800 yards and a horseshoe center that eliminates for fast close-distance shooting. This type of reticle is the most similar to the traditional ACOG sights and is quite comparable to the TA31 ACOG also featured in this article.

The author found that the scope was easy to use and very simple to set up and zero. It has some clever features like an engraved mounting line which allows it to be very quickly indexed to the scope mount of your choice. As far as scopes go, this one is very user-friendly and quite intuitive to use. During the course of testing for this article, the author fired approximately 1,500 rounds and never had a loss of zero, even when shooting from difficult or hasty positions where the scope got bounced around and treated in an indelicate fashion. While its durability has yet to be fully proven on the battlefield, it did pass the MIL-STD810G test.

 The specific contract offered to SIG SAUER by the DoD is to the tune of $12,000,000, which is no small change. The contract was a huge win for SIG SAUER, which as a company is new in the optics game. There is not a tremendous amount of information publicly available regarding the adoption process of this scope. Sources associated with the project told the author that the only real differences between the commercial and military versions were in some very minor details and some markings, but there was no military source available to confirm that. SIG was unable to comment.

Testing the TANGO6T in the Field

For this article, the author built two rifles. One rifle is meant to resemble the M16A4 and features what would have been state-of-the-art technology circa 2005 to 2012. There are some parts in it that are simply cosmetic, but the function and accuracy standards meet or exceed Marine Corps standards. The rifle is capable of firing half-inch groups at 100m using Black Hills MK 262 77-grain ammunition. The accuracy standard was established using a Leupold Mark 5HD 5-25×56 scope. Velocity was calculated at 2813fps. For the purposes of this article, a military duplicate TA31 ACOG was mounted and zeroed for 100m using the same MK 262 ammunition.

The second rifle built, while made from comparable commercial parts, was meant to represent the most modern of military features. It is something of a hybrid build using the M27 IAR (Infantry Automatic Rifle) as inspiration for the lower receiver and the URG-I receiver group currently being delivered to USASOC for the upper. While it is not identical, many of the parts used in it are the same as currently issued. Both rifles in this article use parts 100% sourced from Brownells, which should make it easy if you choose to build something similar.

The two rifles featured here are built completely from parts from Brownells. Note that both have Brownells replica receivers for added authenticity.

The second rifle was also tested using Black Hills MK 262 77-grain ammunition. In a similar test, the rifle was fired at 100m with the Mark 5HD scope. Its average group was three quarters of an inch for five shots. Velocity was calculated at 2720fps. Then it received the SIG SAUER TANGO6 in a Geissele Automatics Super Precision® mount. It was then zeroed at 100m.

The finished Military Hybrid build has features taken from both the Marine’s M27 IAR and the elusive Geissele URG-I receiver group. The 16-inch rifle is a perfect host to the TANGO6T.

Both of these rifles were fired at distances of out to 800m, with the majority of testing taking place inside 500m. This was designed to simulate combat scenarios. The guns were fired at steel plates and cardboard IDPA targets.

Between the two scopes and rifle setups, is quite easy to see how far technology has marched along in the last decade. Even though the M16A4 build was very easy to handle and very accurate, it was found generally lacking by direct comparison, despite the fact that it was more accurate on paper and delivered higher velocity. What it really came down to was the flexibility of the optic.

The ACOG, while rugged and reliable, is not a scope that is meant to be dialed in for windage and elevation in a fight. It is meant for speed and lethality in various light and environmental conditions. Using a 100m zero, the author was easily able to engage targets out to 500m without much of a fuss. After 500m, the BDC  (Bullet Drop Compensator) began to separate from the trajectory of the bullets, and it was difficult to keep rounds on target out to 800m. The hit ratio on man-size targets from 50m to 500m was 80%, which was excellent considering that the targets were at known distance points. At ranges past 500m, the likelihood of hits began to drop considerably when engaging targets. The graduations on the reticle just weren’t precise enough to allow for easy holds when wind and mirage were taken into account. Overall, the ACOG is an excellent optic and has earned its reputation.

The reticle is crisp and easy to use. Note a 10-inch steel plate 200m downrange.

Our hybrid military build did significantly better thanks to the flexibility of the TANGO6T. The fact that it behaves in a similar way to the ACOG at ranges from 50m to 500m was great, but it truly began to shine at distances past that. Because of the fact that the author knew the velocity of the bullets, he was able to very easily translate precise drop points to the reticle of the scope. Making small adjustments was much easier thanks to the fact that the turrets allow for easy and fast adjustment. While the extra magnification was nice, it was not enough to be considered a significant upgrade over the ACOG. In fact, the author did much of his shooting with the TANGO6T at 4 or 5 power just because of the wide field of view he prefers.

Medium Range Performance

For the next series of tests, the author took the two rifles to a shorter distance range of 200m. There were berms at 100m and 150m as well. These drills assess how well the scope did in a close-range scenario against multiple targets.

The M16A4 with the ACOG went first. The rifle was well-built and was a very smooth shooter. The longer gas system and buffer tube make for an excellent, very soft shooting rifle. The only real downside to the set-up is how short the eye relief is on the ACOG. You really have to get your eye right up to it to see a full field of view.

Because of how close the optic is to the shooter’s eye, it can be slightly uncomfortable in the case that the rifle is not properly in the shoulder pocket or an awkward position is assumed. While the rifle built for this article had almost no recoil, it can be distracting to have something so close to your eye while shooting rapidly.

Using the 100m zero, all that the shooter must do is simply put the Chevron in the center of their target out to 200m and fire. This is very fast, and the illuminated Chevron is very easy to pick up. Shooting at these shorter distances with the ACOG is like shooting with a magnified red dot. You can be quite precise if you take your time and aim, but it is much to your advantage to simply center on the body of the target and fire. Overall, it was hard to miss from most field positions.

An advantage of the ACOG is that it takes advantage of the Bindon Aiming Concept which allows for both-eyes-open shooting. This is part of what makes the design so fast. There are some shooters who swear by this shooting style, and it is very easy to see why they do. The M16A4 with an ACOG mounted is one of the most comfortable and accurate combinations ever fielded in modern warfare.

With the M16A4 and ACOG freshly tested, the author knew that the TANGO6T had a steep hill to fight. Unlike the ACOG, there is plenty of eye relief to be had with the TANGO6T. The scope was positioned further forward than the ACOG, which allowed for a more relaxed feel when shouldering the rifle. Because of the fact that it was so easy and comfortable to get behind, the scope was a pleasure to shoot at these closer distances.

Again, the author did not spend much time on 6 power. These closer targets demanded speed and visual acuity. Because of the fact that there is not a significant difference in bullet drop between the M16A4 and the military hybrid to build at closer range, it really came down to speed of target acquisition. The TANGO6T is a conventional scope in that it really is meant to be used with one eye closed. That is not to say it cannot be used quickly.

Because of the way the horseshoe reticle is laid out, there is a visible gap below the center dot used for zeroing. This means that, unlike the ACOG, you can be more precise at closer distances. The ACOG reticle, while useful, has a Chevron that interrupts fine aiming points at medium distance. The author counts this as an advantage for the TANGO6T.

At medium distance, the newer scope did not show a significant enough advantage for the author to declare it a winner; although it was easily on par with the established standard. In the next series of tests, the author moved to a 25-yard pistol bay to practice some close-quarters drills.

CQB Distance Crucible

The 25-yard range is where the two rifles and their scopes saw the heaviest round count. By the end of this test for this article, the two rifles saw a combined total of nearly 3,000 rounds. The goal was to see how they would perform when hot and dirty.

An assortment of combat drills were used to test the TANGO6T. At these closer ranges, the author kept the scope 2x magnification with the illumination turned all the way up for bright daylight. It was a very hot day when the testing was conducted, and there was a significant amount of heat coming off of the barrels of both rifles. These were harsh conditions for any gun, not just the rugged examples built for this article.

When shooting quickly at short distance, the M16A4 build was again quite comfortable to shoot, but it was slower to swing onto target, and the eye relief of the ACOG again became a liability to performance. If you move your head too far back along the stock, you lose the full-sight picture through the optic. The both-eyes-open feature was great here.

Our hybrid military build performed extraordinarily well thanks to the fact that it had an adjustable stock and the TANGO6T’s excellent eye relief. When shooting at the short distances, the newer scope had the propensity to give a double image when using a both-eyes-open shooting style. When using a more conventional aiming style with one eye closed, the TANGO6T performed extremely well.

The TANGO6T is the latest in a long line of military optics dating back to the era before WWI. Will it stand up to the test of time or be forgotten in favor of the next advancement?

Closing Thoughts

As far as military end-use goes, the author believes that the U.S. Army has made an excellent choice with the TANGO6T in its intended Squad Designated Marksman Rifle role. The modern SDMR systems that use this scope will bring a significant advantage to our warfighters simply by means of user-friendliness and simplicity. The scope is very easy to learn and allows the marksman to rapidly and easily engage targets from CQB distances out to a half-mile. As far as civilian end-use, the scope offers a number of benefits to competition shooters and hunters.