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Thread: Explanation of Co-Witness

  1. #181
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    Quote Originally Posted by AR15freak View Post
    I never understood why some would want a lower 1/3 co witness. I only want to have one point of aim when I look through the scope, not two separate ones. BUIS means backup.. Point is that iron sights used to be the primary sighting system for fighting rifles, but now they are used more as a backup option should your red dot fail. Since the human eye picks up the red dot quicker than an iron sight post it makes sense to use it as your main sighting system.. However since the BUIS are in a fixed position on the rifle and don't move, you need to sight them in first, then align the red dot to the BUIS.. I have always done it that way, it was taught to me that way, and I believe that is the right way.. however others with far more experience than me may do things differently. If it works then more power to them.
    on lower 1/3, Me personally, I do not like flip up sights. I have some on my work gun because I am told what to use. My personal gun has Troy HK style (Rounded hood) battle sights fixed. I like them much more than std ar front sight post (V type). Having fixed front and rear, lower 1/3 is much better or has a cleaner view. It works for me and i really like it. It may not or does not have to work for you but you may want to try it. Not just a few shots but run it for a while.

    IMO, co witness does not mean they meet eachother when sighting, it simply means, viewed together (inside the RDS window).

  2. #182
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    I use co-witnessing as a tool to get a newly-mounted red dot in the neighborhood of the already-zeroed irons before I go out to fine-tune the red dot.

    Then, I fine-tune-zero the red dot independently.

    I don't worry about keeping my irons and red dot in agreement, especially when using a quick-detach mount for the dot. If my dot fails, I will detach it and use the irons. If for some unforeseen reason I'm forced to aim the irons through the glass because I don't have time or am otherwise unable to remove the glass, then my approach is obviously not optimal in the cases where the glass slightly shifts the iron picture.

    If my red dot and irons agree after I've zeroed them independently, great, but I don't expect them to agree.

    In other words, I treat the two aiming systems as independent systems that I use and zero independently.

  3. #183
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    I'm a firm believer in the co-witness application but I don't understand the normal person wanting to put 45 degree sights on their AR. I can understand if your shoot 3 gun or involved in a run and gun other than that it seems like a pain in the rear.

  4. #184
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    Ok so now I'm confused...let me start by saying forgive my ignorance. Hopefully someone can help me understand...

    Am I to understand this cowitness business only applies when the rear sight is not in play?

    With rear sights up I turn on the HWS, the dot sits on top of the post like a dumdum sucker -Absolute. I like.

    Rear sights down, my view in window is more like a 1/3. Mind you my model Eotech (517) has side buttons, and a 7mm built in riser forcing me into a 1/3. (I learned this about 30 mins ago, source Eotech.

    Sights: A2 front, MBUS pro flip in the rear. Eotech 517, vortex vmx-3 magnifier.

    Why does it all appear to be absolute cowitness with rear sights up only? I guess I have to mount the magnifier with shim for 1/3 to be in line with hws? My face hurts from over thinking this.

    Sent from my E6810 using Tapatalk

  5. #185
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    "Absolute" and "Lower 1/3" describes where in the field of view in RDS the front & rear sight line up.

    "Absolute" means the front and rear line up in the center. With the rear flipped down, the dot will sit on top of the post in the center.

    "Lower 1/3" means they line up in the lower third. With the rear flipped down the dot will sit on top of the front sight in the lower third. If the dot is in the center, there will be a space between the dot and the front sight post.
    Last edited by MistWolf; 12-19-18 at 12:10.
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  6. #186
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    Hieght over bore must be considered.

    If you co-witness your iron sights or red dot using the other as the POA, you have not accounted for the difference in the height of each sight's Point of Aim from each other. Unless your dot aligns perfectly with the front sight at the same height above the bore of the barrel, there will be a difference in point of impact at ranges beyond the zero range. Each set should be zeroed independently of the other and then left alone. That way they will be more likely to be in synch at short to moderately not so short ranges. They will never be 100 percent in synch at all ranges because each has a different height above the bore line that needs to be accounted for in the trajectory. At short ranges you may not notice much difference, but the longer the range the greater the variation between each other in hold over required.
    It's just physics. The fact that the irons only show in the bottom 1/3 rd confirms this situation. They would have to be in the exact middle of your red dot to be truly co witnessed and have the same hold overs at longer ranges.

    Look at all the Trajectory calculators on the web. One of the questions required is the height of the optical center of the sight over the center of the barrel bore.
    Last edited by SilverBear; 01-25-19 at 23:55. Reason: exactitude of terminology correction

  7. #187
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    Hope this helps,
    Attached Images Attached Images

  8. #188
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    Just a thought, if you have no iron sights and your red dot goes dead, I'll bet that if you center your target in the red dot tube field of view that you will hit your target (person sized target) quite easily at 50 to 100 yards. Personally I don't like the clutter of the co-witness iron sights in the RDS field of view. Just another distraction.

  9. #189
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    Quote Originally Posted by SilverBear View Post
    Just a thought, if you have no iron sights and your red dot goes dead, I'll bet that if you center your target in the red dot tube field of view that you will hit your target (person sized target) quite easily at 50 to 100 yards. Personally I don't like the clutter of the co-witness iron sights in the RDS field of view. Just another distraction.
    A dead CQO being used as an impromptu giant peep sight? I'd like to see a video of this one at 50 to 100 yards on steel that's been freshly painted.

  10. #190
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    Quote Originally Posted by FightinQ View Post
    A dead CQO being used as an impromptu giant peep sight? I'd like to see a video of this one at 50 to 100 yards on steel that's been freshly painted.
    How big of a piece am I gonna need...

    Sent from my E6810 using Tapatalk

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