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Trijicon ACOG 4x32mm Green Crosshair Reticle – TA31-C-100413

The Trijicon ACOG (Advanced Combat Optical Gunsight) is a fixed power, compact riflescope with an illuminated reticle pattern for use in bright to low or no light. The ACOG is designed to be extremely durable and reliable. Combining traditional, precise distance marksmanship with CQB speed, many variants include a bullet drop compensated (BDC) reticle. Undoubtedly, every feature of its design was chosen for a single purpose, to provide increased hit potential in all lighting conditions.

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This 4 x 32 BAC ACOG scope provides a dual illuminated reticle using fiber optics and tritium for a bright aiming point in any light condition. It allows the user to instantly switch between supersonic and subsonic ammunition without having to re-zero the optic. The supersonic BDC (out to 600 yds.) has been merged with the subsonic BDC (out to 200 yds.) to provide one set of aiming points for both types of ammunition. The reticle drops are based on an average of commonly available off the shelf subsonic and supersonic ammunition from a 16″ barrel. This BDC reticle is not limited to one or two specific bullets: a majority of commonly available ammunition will fall within the 2 MOA diamond aiming points.

Battery Free Illumination

It features a tritium and fiber optic illuminated reticle that automatically adjusts the brightness based on available light.

Rugged Aluminum Alloy Housing
Forged 7075-T6 aircraft aluminum alloy housing it provides for a nearly indestructible sighting system.

“Both Eyes Open” Design
The ACOG can be used as a CQB sight when shooting “both eyes open,” utilizing the Bindon Aiming Concept (see below).

Fixed Magnification
Fewer moving parts than a variable optic equals more durability.

Combat Proven
No other magnified optic has been used more in combat than the ACOG.

Shock Resistant
Proven to withstand recoil from a .22LR to a .50BMG. Passes U.S. Military drop test requirements.

It is filled with dry Nitrogen to eliminate fogging. Five times more waterproof than military standard requirements.

Limited Lifetime Warranty
Tritium lamp is warranted to illuminate for 15 years on fiber optic scopes and 10 years on non fiber optic scopes.

Bindon Aiming Concept

Traditionally, “both eyes open” aiming has been widely used with iron sights or reflex style sights, but use with a magnified scope was often deemed unlikely. But, The Bindon Aiming Concept (BAC) is a method of combining “both eyes open” aiming while using a magnified scope.

Because shooting with “both eyes open” offers several advantages to the user,  better situational awareness, a far greater sense of balance, a wider field of view, and far less eye strain. These advantages aid the shooter in quick target acquisition and improved shooting performance.

Utilizing BAC

When tracking a moving target with your shooting eye through a  riflescope, the image appears blurry as the riflescope moves due to the magnification. This blurriness forces the brain to automatically switch eye focus and take in target data from the non shooting eye (non magnified). The reticle remains visible in the shooting eye and your brain will superimpose the aiming point onto the non magnified target.

 So, when you bring the weapon onto the target, the target will “zoom” in, allowing you to identify and engage more accurately. This aiming concept happens naturally, without conscious thought, for those with equal or close to equal vision in both eyes.

Finding Your Dominant Eye

  1. First, OPEN BOTH EYES, and hold you index finger out in front of you line of sight on a fixed object.
  2. Next, CLOSE your non shooting eye and note the position of finger on target.
  3. Then OPEN BOTH eyes, keeping finger on target.
  4. Finally, CLOSE opposite eye and note position of finger on target.

The TA31 also includes:

Flattop Mount (TA51)
4 x 32 Scope coat (TA64)
Lanyard Assembly for Adjuster Caps (TA71E)
Trijicon Logo Sticker (PR15)
ACOG Manual
Warranty Card


Magnification 4x
Objective Size 32 mm
Bullet Drop Compensator Yes
Length 5.8 in
Weight 9.9 oz
Illumination Source Fiber Optics and Tritium
Reticle Pattern Crosshair
Day Reticle Color Green
Night Reticle Color Green
Calibration 0.223
Bindon Aiming Concept Yes
Eye Relief (in) 1.5
Exit Pupil (mm) 8 mm
Field of View
Field of View @ 100 yard 36.8 ft
Adjustment @ 100 yards 2 clicks per in
Mount TA51
Mount Comes With TA51
Housing Material Forged Aluminum