ACOG TA31F: Intial Thoughts

ACOG TA31F: Intial Thoughts

Going used was a good decision. The ACOG is a product that is built tough enough to stand a lifetime of use. The forging of the aluminum housing is solid, and it is as if the optical components themselves were set in stone. There is heft and solidity to the ACOG that can be appreciated upon picking it up. Like many readers, I had only seen genuine ACOG’s once or twice in person. It was really difficult to, without having ever “test drove” one, spend even what I did on a used model. As a piece of equipment, it is substantial in build quality.

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The ACOG weighs 14 oz with included TA51 mount. The glass is clear with a chevron reticule and gradually fading red stadia lines. The tritium from this specimen is quickly picked up by a non-light adapted eye. Very bright stuff.

It has finger adjustable 1/2MOA adjustments hidden under the caps.

Eye relief is 1.5 inches. The optic is quick to acquire so long as either A) you, your ACOG, and your rifles LOP work  well together or B) you have a adjustable stock. This optic is going on my primary rifle which has a VLTOR A5 stock system. With this setup I can comfortably position the ACOG and adjust my LOP to bring the ACOG quickly to the eye. A fixed stock such as the A2 and shorter arms may pose a challenge. I can see some people having to mount it at the rearmost slot which would preclude using a BUIS.


The rifle’s front sight is a ghost, and definitely not in the way. Pictures online show variable degrees of shadow, but in reality it is an incredibly faint effect.

The illuminated reticule is “red dot” bright in the sun/daytime though there is much less bloom than if I cranked up my COMPM4 to the same intensity.

Pictures online make the stadia lines appear tiny. They are small in the overall sight picture of the ACOG but they are not hard to pick up as pictures online purview. Once your eye swallows the sight picture of the ACOG you can find everything you need quickly.

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Using BAC is somewhat difficult. You bring the optic to the eye, place color on target and fire. All this must be done instantly or the brain will pick up the clearer image of the 4x ACOG. The BAC concept seems to rely on movement. So long as the eye is behind the glass and the rifle is moving everything the dominant eye sees is a blur except for the bright chevron. The left eye can focus on the target / periphery and as soon as the brain superimposes the red color on the target, fire. The manual states not to seek a clear chevron… just put a color / streak / red on target and fire.

Any delay and suddenly your brain will switch to the 4X view and it will slow you down.

My question is, at close range, can I just align myself with the target and fire with reasonable accuracy? Do I need to use BAC at room distance? Does the BAC technique maintain accuracy at 25 yards?

I delayed my range trip to wait on this product. Can’t wait to give it a spin. I will be using it for a couple of months before writing my review. I know it’s good, but everything has an Achilles heel.

Written by lothaen


  1. Shawn · October 6, 2013

    the bAC is a waste of time with a 4X. but, place the chevron at center mass and use it like a RDS. you will see its as easy as using a red dot and its pretty close to being as fast with practice. if you had a lower power ACOG the BAC works out OK, but the 4x is not the best choice. you will see that just using it as normal and using the chevron as a refrence on center mass give fast accurate performance

  2. lothaen · October 6, 2013

    Have you tried using ACOG’s with the lens covers to shoot as if was an OEG for up close? Thoughts?

  3. Recce Rifleman · October 6, 2013

    I use a TA31F myself. A lens cover works wonders for helping to use BAC. In fact, on the “poor man’s ACOGs” like the Primary Arms PAC3X, lens covers come standard and instructions indicate directly the advantage for use with BAC shooting.

    As for your question about reasonable accuracy up close, this link is a pretty good analysis of expected accuracy:

    One of the best remaining investments you can make (if you haven’t already) is a LaRue QD mount. It returns to zero, and that allows you to practice with irons when you want without having to re-zero.

  4. lothaen · October 7, 2013

    It is pretty funny to think that I am looking at upgrades to my upgrade… upgrades are all incremental. 🙂

  5. Brad · November 4, 2013

    I don’t know what model it was, but we use the ACOG in the Marine Corps, mounted on the M4 and the M16A4. We use it from 10 yds all the way to 500. Using it at close range, we are taught not to close our off eye, to use both eyes. Let the red chevron act as a guide instead of a target point. It works amazing at both. I’ve seen one dropped from a single story roof, placed on an M4, and nail center every time. And with the rail system, you can take it off of one rifle, put it on another of the same kind in the same place, and not lose your zero. If I was thinking about tactical shooting, it would be what i wanted on my rifle.

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