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Posted: 12/30/2003 5:56:48 PM EDT
Hi guys, I am trying to learn and understand the Bindon Aming Consept (BAC), but I need to get some facts straight.

I have used a Reflex sight for some years now, and recently purchased an ACOG TA31A to replace my Leopold Vari X-III 1,75-6x scope om my AR15. The reason I chose the ACOG was my impression that I could use the two eye open technique I trained with the Reflex, by aiming "OEG" style through the blurred image.

However, when switcing focus from left to right eye, I see that the aiming point is substantially off to the side, and I would miss smaller targets completely without adjusting aim.

What should happen if I tape over the objective opening of my scope, and zero the sight using a two eye sighting, where my right eye observes the target, and my left eye observes the reticule? Should the zero be the same as if I zero the sight in the normal manner, looking through the magnified scope?

The reflex, Aimpoint and EOtech 1x magnification scopes are parallax free.
The TA31 manual states that the sight is parallax free in the vertical plane. However it does not say any thing about the horizontal plane.

Any input greatly appriciated, I haven't had any range time since I got the scope, and am getting a bit frustrated.
Link Posted: 12/30/2003 9:54:19 PM EDT
For some people it just doesnt line up. The magnification cuases some people difficulty in lining the two pictures up.

BTT so NewARGuy can find this one, he'll know more.
Link Posted: 12/31/2003 1:10:39 AM EDT
I believe what you are describing is what Trijicon calls Phoria(at least that is what they call it in my ta31 manual pg.19). It more less states that the aiming dot from the initial aim can be expected to be a little to the left or right of the final (magnified) aim depending upon your amount of phoria.  Phoria is the slight crossing of the eyes, looking toward each other, when you are looking at a target in the distance.  At least that is what I get from it.  
Link Posted: 12/31/2003 7:38:31 AM EDT
Phoria is a slight crossing of the eyes;  but even if you have 0% phoria, you will still see the dot shift because it is a result of having binocular vision and magnification. If you have phoria,  the difference will be more exaggerated.

The amount the dot shifts for anyone is a certain percentage of the field of view. At close ranges it won't make a difference in impact, at longer ranges it can be way off; but with longer ranges you also have the time to let the image "zoom".

What should happen if I tape over the objective opening of my scope, and zero the sight using a two eye sighting, where my right eye observes the target, and my left eye observes the reticule? Should the zero be the same as if I zero the sight in the normal manner, looking through the magnified scope?
View Quote


If  you do  this, your sighting using weak-eye BAC will be zeroed; but your sighting through the scope will be off by the same amount that  your left eye sighting is right now.


Link Posted: 12/31/2003 10:14:49 AM EDT
It is not possible to use the BAC as a TRUE OEG.  You can approximate it though.  Like you said the side to side parallax might be off based on the spacing of your eyes, etc.  The ACOG scope has a constantly centered reticle.  Moving the scope adjustment will not help you if you have taped over the scopes objective.  The scope zero will be changed, but the OEG effect will remain unchanged.  The actual OEG sight did NOT have a constantly centered reticle.  In fact it was quite annoying with both vertical bullet drop and horizontal parallax changes at various ranges.  If you want to see something hilarious have a left handed shooter shoot with an OEG that was zeroed for a right handed shooter.  He will be extremely off.  That has been my experience.  I used to own an OEG when they were new.  Watch-Six
Link Posted: 12/31/2003 2:02:57 PM EDT
Originally Posted By Strid_223:
Hi guys, I am trying to learn and understand the Bindon Aming Consept (BAC), but I need to get some facts straight.

..............

However, when switcing focus from left to right eye, I see that the aiming point is substantially off to the side, and I would miss smaller targets completely without adjusting aim.

.
View Quote


Remember, BAC is to help you hit big targets, up close, in a hurry, with a magnified optic.

It is not meant for precision shooting on small targets.  If you are trying to hit a small target, you will have to readjust your point of aim when you switch to the magnified view.
Link Posted: 12/31/2003 5:51:05 PM EDT
Thank you all for the input, it has been most informative.

I guess this means that the physical properties of the magnified scope sets limitations on the use of the ACOG as a "blurred" red dot.

I use the rifle for IPSC, practical rifle competition, and the engagement distances varies grately from stage to stage and match to match.

I find variable power scopes to be less than ideal, as you will seldom be able to anticipate the possible engagement distance to an upcoming target in a tactical situation.

I guess my ACOG will be able to fill the "universal" scope role well with a lot of practice. After all, quality wise, it seems like a good choice. However, I guess I got a little carried away with the idea of the BAC on a 4x as a red-dot replacement.
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