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Thread: Cowitness - a first for me.

  1. #21
    Join Date
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    Not unusual IME.
    When I dial in RD and BUIS I’ll dial irons in first and adjust dot dead center L/R and just into FS blade.
    This gets me real close with RD, but seldom, if ever dead nuts “on”.
    Fine tuning is necessary to have the dot “on”.

    I attribute this to tolerances with rail/mount.

  2. #22
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    Jan 2011
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    I use 1/3 co-witness, mine are never right on top of each other.

    Likely because I run them with a different cheek weld. Pressed into the stock running irons, more "heads up" running an RDS.

    Zeroed for how I run them, they're not exactly on top of each other. No biggie as they are ZEROED and hit where they are supposed to.

  3. #23
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    Quote Originally Posted by voiceofreason View Post
    I use 1/3 co-witness, mine are never right on top of each other.

    Likely because I run them with a different cheek weld. Pressed into the stock running irons, more "heads up" running an RDS.

    Zeroed for how I run them, they're not exactly on top of each other. No biggie as they are ZEROED and hit where they are supposed to.
    THIS!!!
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

  4. #24
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    Quote Originally Posted by Eurodriver View Post
    It’s a barrel mounted FSB.



    I can’t tell if you’re serious. In case you are, this has a 10.5” barrel and there’s always a 6+ mph wind.

    I'm serious. I frequently shoot handguns at 100 meters, so zeroing the windage on a RDS at 300 yards with a 10.5" carbine is not far fetched. If your no wind windage zero is on at 300 yards, everything at closer ranges will look good. You are not sacrificing iron sight plane length with a shorter barrel and a RDS.

    The way I have my 16" carbines zeroed, I hold the base of the red dot at the base of the neck on a silhouette at 300 yards and the rounds drop into the middle of the torso. The carbines have Aimpoints with 4 moa dots that are set up for lower 1/3 co-witness.
    Last edited by T2C; 03-26-19 at 16:47.
    Train 2 Win

  5. #25
    Join Date
    Oct 2016
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    I just ordered my first 1/3 co witness mount from Scalarworks. Im thinking I will like it.

  6. #26
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    I went through this years ago, and it bugs me too.

    Sample of one brand, but several rifles, all BCM. I sort of wish I'd kept my fixed backup sights long enough to see what happens with a Colt carbine.

    The rear backup sight that seemed to allow perfect alignment over the dot on any rifle was the LaRue LT103. DD 1.5's didn't do it, neither did "chopped carry handle" LMT backup sights. IIRC the MagPul folding MBUS did it on some rifles and not others.

    This is one reason I only use the front sight for reference now. I use a folding BUIS at the rear and when I shoot I try to center the dot over the front sight post as much as possible. The rear MBUS stays folded, as in DOWN.

    A worse thing is to zero your rifle with the rear sight folded, then deploy the rear sight and find the dot isn't in the same place in the optic's window as it is without the rear sight. This gets back to the RDS parallax issue since when co-witnessing at 1/3 you're forcing the red dot into the lower part of the lense.

    That's when I said, "Eff it" and just started using the front sight for reference.

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