The Bindon Aiming Concept (BAC) Explained – Shooting With Both Eyes Open

Running a telescopic sight on a rifle or carbine is a great way to increase its effective range and accuracy. The magnified image that’s created when looking through the scope, paired with a reticle and good zero, help shooters get pinpoint shot placement that’s repeatable round after round.

Equipping one is a sure way to push your shot distances further than irons or a dot sight – you’ll be hitting targets a few hundred yards out with ease. However, with all its benefits, there are a few difficulties that shooters encounter when using a scope. Most notable are the issues that get introduced as a result of scope’s reduced field of view.

The Need for Two Eye Shooting

two eyes open shooting

Its a common fact with all magnified optics that target acquisition and target tracking is a challenge – and its easy to understand why. When looking through a scope the observable field of view is greatly reduced compared to a non-magnified optic, or the naked eye. A scope’s field of view is measured as the amount of area seen from left to right at 100 yards. As magnification level increases, this cross area gets smaller and smaller – at 10x zoom you’ll be around 3.3m of area at 100 yards, 20x will give you ~1.8m. So while the scope magnifies your target the tradeoff is that you can’t see as much of the area surrounding it.

The ‘tube effect’ also plays a role in vision impairment. With the primary eye looking through the lens, the scope’s tube walls essentially cut off all peripheral vision of the shooter. These combined factors mean the shooter is always limited to viewing a very small portion of the area downrange at any given moment.

If you’re shooting at static targets from a bench this may not be too much of an issue, but when trying to pick up targets fast, or follow moving ones – especially while hunting – you’ll experience the trouble that this lack of visibility causes. Trying to find a target through your scope often ends up in a lot of scanning back and forth down range before you actually see it, or worse, lose it all together. To deal with this problem the Bindon Aiming Concept was conceived.

How the Bindon Aiming Concept Works

The BAC was developed by Glyn Bindon, the founder of Trijicon, and is a method for ‘two eyes open’ shooting with a magnified optic. When done correctly it allows the shooter to incorporate their non-shooting eye to provide the wide field of view that their shooting-eye lacks while looking through a scope.

The BAC works as such: As the shooter moves their scope to track a target with both eyes open, the image observed through it by the shooting eye becomes blurry due to the fast magnified motion. When this happens the brain will adjust to primarily take in the view from the non-shooting (and non-magnified) eye, which sees a much wider FOV. By using a scope with a bright reticle, the reticle remains visible in the shooting eye and gets merged into the non-magnified view.

Essentially, the brain takes the two images of the target scene – one from each eye – and combines them, pulling the non-magnified view from the non-shooting eye, and the reticle from the shooting eye, to create on combined image. The end result is the shooter seeing a non-magnified view with the reticle still present.

When the weapon settles on a target and becomes still, the brain readjusts back to primarily taking in the view from the shooting eye, allowing the shooter to use the scope as intended. Shooters who practice this method are able to track targets as they move downrange without losing them. The whole process is a natural effect that takes place within the brain, all the shooter needs is two eyes and a bright reticle to make it work.

What Optics Can Be Used?

As we mentioned above, the main requirement for an optic to be usable with the Bindon Aiming Concept is a reticle that gives sufficient contrast to the background. In some cases a thick crosshair can be enough, but typically the BAC calls for a brightly illuminated reticle – one that really stands out in the FOV and is easy to pick up with the primary eye. The best option is a solid red dot that takes up a few MOA.

Illuminated reticles can be found on a number of different optics, but this feature is something that Trijicon scopes in particular are best know for. Trijicon has made a name for itself by producing scopes with high-visibility reticles that are powered by some unique methods. From internal battery and fiber optics, to tritium lamps and solar cells, Trijicon has been a leader in developing new technologies for powering reticles to keep them consistently bright under any condition – from the washed out light of day to the darkness of night. Most Trijicon scopes utilize a combination of these methods to deliver an always-on, bright reticle which makes them well suited for this aiming concept.

Trijicon ACOG 4×32

trijicon acogThe Trijicon 4×32 ACOG is the scope most associated with the BAC, mainly because it is Trijicon’s most popular model. These scopes are built to US Military and NATO specs and are currently serviced in multiple branches – including being outfitted on each Squad Designated Marskman Rifle in the Army.

Usually a 4x scope wouldn’t be effective in CQB situations where action is happening fast and close -you just don’t need that much magnification when engaging targets that are only meters away. Typically for short distances a non-magnified red dot is preferred for its fast target acquisition speed. However, by utilizing the Bindon Aiming Concept, the ACOG can double as a suitable close quarters battle sight. Shooters can aim with both eyes open and the ACOG performs more like a non-magnified red dot than a scope.

The ACOG’s reticle is powered by a combination of fiber optic and tritium. The fiber optic is exposed across the top of the scope and in daylight it gathers incident light and pipes it to the reticle. When there is insufficient ambient light the reticle is then primarily powered by internal tritium lamps. The popular ‘chevron’ shaped reticle remains bright at all times which lets the BAC work so well.

Trijicon Accupoint

trijicon 1The Trijicon Accupoint series can also make use of the BAC when going after long range targets. The Accupoint is better suited for distance shots and hunting than the ACOG because of the magnification ranges its available in: 1-4×40, 2.5-10×56, 3-9×40, 5-20×50.

Especially at large magnifications greater than 10x, the field of view is so reduced that implementing the BAC can make everything easier. If your tracking game through the sight all it takes is opening the non-dominant eye to get a better situational awareness of where its moving to.

This scope also uses embedded tritium and fiber optic to keep the reticle powered at all times – no battery required. There are four reticle patterns available that include a triangle post, mil-dot crosshair, standard duplex crosshair, and German crosshair. With each of these the center point is what is illuminated.

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