Co-Witness

Discussion in 'AR-15 Discussion' started by DiveFlyFun, Apr 2, 2009.

  1. DiveFlyFun

    DiveFlyFun New Member

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    Does anyone one know what the "elevation" (distance form top of rail to bottom of circumference) and "line-of-sight" (distance form top of rail to dead center) heights are for "absolute co-witness" and "co-witness" on a 30mm sight/scope?

    by my calculations:

    "Absolute Co-Witness"
    The rear sights "line-of-sight" is 35mm high.
    The center of the 30mm circumference is 15mm.
    15mm - 35mm = 20 elevation

    "Lower 1/3 "Co-Witness"
    Would add 3-4mm to the 20mm above to be able to see it go over the rear aperture.
    So its elevation would be 23-24mm

    Does that look right? For some reason everybody hides these numbers on their claims of "co-witness"

    Thanks!
     
  2. crockett007

    crockett007 New Member

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  3. RL357Mag

    RL357Mag New Member

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    Ditto! What kind of gun are you talking about, what kind of optic are you talking about?

    If you are discussing co-witnessing of BUIS with a scope, there is no concern, since the focal distance of the scope will not allow the front sight to come into focus or obscure your sight picture while looking through the scope. If you are talking about a rail mounted Holosight or similar optical device mounted in line with BUIS, the optical axis or "centerline" of the lens must be higher than an imaginary line extending from the top of the front sight to the top of the rear sight. But without knowing what type of gun, sights, or optical sight you are referrencing, any advice is impossible.
     
  4. DiveFlyFun

    DiveFlyFun New Member

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    Sorry, my bad....An AR-15 Bushmaster Patrolman (M4A3) with a 30mm red dot.
     
  5. RL357Mag

    RL357Mag New Member

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    You should have no problem with co-witnessing to a 30mm red dot as long as the center axis of the red dot is slightly higher than the front sight elevation.