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cowitness advice; 20" AR 55gr M193

Discussion in 'Rifle Country' started by Lucky, Apr 21, 2009.

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  1. Lucky

    Lucky Member

    Joined:
    Jul 12, 2005
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    Location:
    Calgary, near Rocky Mountains - Canada
    What is the sight height over bore on the M16a1? I have a Trijicon with a 12.5 moa (tall) triangle which is stated to be mounted 0.22" above the M16(a1) sight plane.

    I calculate the sides of the reticule will show exactly 20" width at 125m. Something incorporating this could be helpful. But I would like the top of the triangle to correspond with the apogee of the ballistic trajectory.

    At what zero distance could I create the best trajectory to take advantage of the holdovers the reticule can provide?


    reticule:
    tall 12.5moa=~3.636mils
    wide 13.9754moa=~4.065mils

    I figure the triangle will be 7" wide at 43.75m, and 20" wide at 125.0m
     
  2. Lucky

    Lucky Member

    Joined:
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    Messages:
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    Location:
    Calgary, near Rocky Mountains - Canada
    Maybe title should be Zero Advice - that's what it's got

    [​IMG]

    Ok just trying to bounce ideas off anyone who'd know;

    *AR15 sight plane is 2.6 inches high? (I'm using this # for Remington Shoot program)


    Zero at 16m using the bottom of the triangle looks to give a trajectory that stays within the 12.5moa height all the way out to 450m, more than sufficient. But a little too simplistic.

    Zero at 26m using the middle of the triangle and at 100m it will hit 6.33 inches high, which is right with the top of the triangle, assuming you use half of it's height (6.25moa). The apogee comes within the triangle at 200m and just under 10 inches, which puts it within the triangle. And then the bottom of the triangle could be used as an aiming point at 370m.

    *Big question: How come online manuals talk about 25m zeroes producing flat trajectories that never stray more than 3"??? 10 inches is more than 3 inches.


    Similarly if zeroed (center of triangle) at 23m the apogee could coincide with the tip of the triangle at 200m, 12.5 inches high. And then the base could be used for aiming at 400m. This has the effect of making the rounds hit 1.5" high at 100m and 1" at 150m though.

    *Is this a better trade off than the 26m zero, where at 200m your bullets will strike below POA (inside the triangle)? Am I right to assume, with a solid reticule that could obscure vision, calculated strikes above POA are better than below?
     

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