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Posted: 5/8/2018 2:33:12 PM EDT
[Last Edit: 5/8/2018 2:56:18 PM EDT by acogta110]
Phoria is a known problem for those of us using ACOGs up close. Our shots can be 10" or more off our target at distances of 25 yds. For this reason, many people say BAC doesn't work.

I remember reading how one Marine said they are trained for CQB with their ACOGs - "Keep both eyes open and break the shot the VERY INSTANT you see the splash of the reticle on target".

That is secret #1. I have tested and proven this to myself. If I wait even 1-2 seconds to break the shot, phoria kicks in and my eye drifts sending my shot down and to the left. If I break the shot the millisecond I put the reticle on target, I get hits equal to what I would get with a red dot.

Secret #2 is having the ability to dial up the intensity on my reticle (LED ACOG). In separate tests, the dimmer my reticle was, the faster and more severe the offset due to phoria. A nuclear bright reticle gave me better hits on targets within 25 yards snap shooting.


1. Break the shot instantly. Even 1-2 seconds is too slow.
2. Bright reticle.
Link Posted: 5/8/2018 2:50:07 PM EDT
[Last Edit: 5/8/2018 2:58:07 PM EDT by acogta110]
Here is a test that will help show the time aspect of phoria. Phoria takes time to take effect.


1. Find a spot on the wall about 15 feet away. Focus on it with both eyes open.
2. Cover your right eye with a 3x5 card.
3. Leave it covered for a few seconds.
4. Quickly move the card to cover your left eye.

I'll bet the spot appeared to move. Just for fun, you can cover the left eye first and move the card to the right eye. You may see a difference in the magnitude of the shift if one eye is worse than the other.


Now, here is a way to show that it takes time for the phoria to kick in.

1. Focus on the same spot on the wall with both eyes open.
2. Take the 3x5 card and quickly move it back and forth, alternating covering your left and right eye.

The spot doesn't move.

For extra credit, in the second test, you can gradually slow down the movement of the card back and forth until you see the dot appear to shift position. This will tell you how much time you have to break your shot.
Link Posted: 5/8/2018 4:55:08 PM EDT
All very true. That’s why I’m loving my Browe. The reticle is always auto adjusting to be bright enough for BAC. If you can find the reticle without getting “inside the scope” BAC works at across the room distances.

I’d add# 3. Get back off the scope. The further out the scope is the less shift I notice. I doesn’t matter if you have your full field of view in the optic as the goal here is to stay “ out of the optic”
Link Posted: 5/8/2018 5:05:26 PM EDT
Inkya - that is a great point. I have found the same thing to be true. If I back my head off the scope, it improves my POI / POA.
Link Posted: 5/9/2018 12:20:26 AM EDT
Speed, comfort, not being up too much on the scope (nose just off or bouncing off the CH), and actually looking with both eyes (hard for some people) while scanning for targets all help greatly.
Your brain sees the most detailed view, the unmagnified one, preferentially, until you stop moving the rifle, then it prefers the even more detailed magnified one which is no longer blurred from motion.
With practice your brain will switch so fast from the unmagnified view to the magnified one as soon as the scope stops on a spot that you almost can't shoot fast enough.. You will notice that
the shot taken the instance the donut is on target, using BAC, will match the precise POI of the magnified view.

It's hard to explain, but to use BAC to it's best effect, after becoming proficient with the scope you almost have to keep the rifle moving, even if it's just barely circling, otherwise you can lose the RDS (OEG) effect,
or encounter "phoria" and the problem of dot drift.

After enough practice, familiarity, you, or at least some, can actually switch the mind's view at will, without moving the rifle. And without degradation of accuracy. If you have POI offset under these circumstances,
keep training, for many either it goes away or you can almost unconsciously adapt your POI.

Many dis the TA55 ACOG because of it's size and moderate magnification, but it's super bright high contrast image with the 5.5X mag (blurs easy on movement) makes it among the easiest to master BAC with.
I am most comfortable with the TA11C I use on the Recon, and the advantages that it matches MK262 out of my 16" is a big plus.
But I run BAC with the TA31F just as well, even though I have trained with it less.
A TA31 is probably the best choice for most users.
Link Posted: 5/9/2018 11:30:29 AM EDT
I agree with your observation that the higher the magnification is, the easier unoccluded BAC is. I can't use BAC with anything below 2.5x for that reason. My right eye takes over even when scanning and makes me feel drunk.
Link Posted: 5/9/2018 12:58:43 PM EDT
That is basically just understanding how BAC actually works. Once the sight settles the brain will trainsition to the zoomed in sight picture. If you don’t learn how to focus your sight on each image the brain will marrying the images weirdly and throw shots. Took me forever to get it down
Link Posted: 5/9/2018 1:57:33 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hoody2shoez:
That is basically just understanding how BAC actually works. Once the sight settles the brain will trainsition to the zoomed in sight picture. If you don’t learn how to focus your sight on each image the brain will marrying the images weirdly and throw shots. Took me forever to get it down
View Quote
Shhhhhh just let it happen.jpg

First thing I noticed about the ACOG very weird/cool when you realize that you dont realize your sign picture is automatically shifting from open eye to the zoomed sight picture.
Link Posted: 5/9/2018 2:12:27 PM EDT
I always flip the front cap down and close the scope off then just kind of look past the scope to the target and super impose the red splotch on the area I want to hit. Im not super accurate but at room distances Im good enough
Link Posted: 5/10/2018 11:48:54 AM EDT
I think there is a lot of confusion among ACOG owners. BAC shooting is NOT the same as occluded shooting.

They are two very different things. For a right handed shooter:

BAC - Two eyes are open. When the scope is moving, the left eye sees the target. The right eye sees a blur. The instant the scope stops moving, the right eye takes over seeing the magnified image of the target through the scope.

Occluded - Two eyes are open. However, at no point can the right eye get a sight picture. The right eye cannot see through the scope.

Ways to shoot occluded:

1. Scope cover
2. Dark conditions
3. Head position such that you can see the reticle in the ACOG. But, your right eye cannot see through the scope. There is a sweet spot for head positioning that allows this.
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