Lynx Defense

Is Chris Costa wrong? Any physics majors in the house?

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  • SA Justin

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    At about the 58:15 mark. The explanation on holding left or right... Maybe I'm confused but is he saying gravity tilts when you tilt and all of a sudden the bullet drops left or right?

    Correct me if I'm wrong but as long as your windage is dialed in, you would still hold high or low depending on the distance. Never left or right, right?

    My head hurts....
    Lynx Defense
     

    Mic

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    No, what he is saying is that because the optics or sights are above the axis of the barrel, it will throw off your point of aim/point of impact.
    When you are shooting normally and your target is closer to you than the distance the rifle was zeroed at, the bullets will be below it. When you get the gun sideways, this moves with you. It's the bore axis vs sight axis, not gravity.
     

    SA Justin

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    No, what he is saying is that because the optics or sights are above the axis of the barrel, it will throw off your point of aim/point of impact.
    When you are shooting normally and your target is closer to you than the distance the rifle was zeroed at, the bullets will be below it. When you get the gun sideways, this moves with you. It's the bore axis vs sight axis, not gravity.

    Thanks for the explanation. I gotcha.

    Interesting... I'll have to remember than if I ever want to shoot a zombie while spooning with a hot chick. :)
     
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    Acera

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    He talks about a 50 yard zero, but if I remember correctly did those guys not promote a 36 or 38 yard zero for ARs at one time??

    Had a video of something like that but can't find it now for some reason.
     

    Renegade

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    What he is saying is if your gun has a 50 yd zero and you are closer than 50, your POI is lower. Let say 1/2 inch. I think we all understand that.

    If you rotate your gun 90 degrees right (ejection port is facing down), the rounds will still be 1/2 inch low, but to the left and you need to compensate for that.
     

    Renegade

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    He talks about a 50 yard zero, but if I remember correctly did those guys not promote a 36 or 38 yard zero for ARs at one time??

    Had a video of something like that but can't find it now for some reason.

    I am not an uber cool instructor, but I promote a true BSZ and that depends upon sight height and MV. That is usually in the 40-44 yard range for a typical AR shooting M193 and Aimpoint 2.6 inches high.
     

    Acera

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    I am not an uber cool instructor, but I promote a true BSZ and that depends upon sight height and MV. That is usually in the 40-44 yard range for a typical AR shooting M193 and Aimpoint 2.6 inches high.

    Actaully I have found some stuff on it, it was Travis Haley talking about a 36 yard zero for ARs with red dot sights. Seems that distance is a pretty good set up for multiple shooting situations/ranges likely to be faced with during an encounter. Can't find the video, but find references to it.............

    GoogleFu is broken with me tonight :(


    I can find the thread here I posted when it first came out, but the video link is wrong now.
    http://www.texasguntalk.com/forums/rifles/39709-ar-carbine-zero-distance-video-print.html
     
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    Acera

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    Found this, one of the best depictions of how sights work I have seen. Lots of new folks don't understand this.

    xuhqpttxnv.jpg



    Shamelessly stolen from this good thread on the subject over at M4Carbine.net
    AR-15 Zeros and Trajectories
     

    Big Phil

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    SATX
    In his video with Panteo, Haley discusses multiple zeroes but doesn't necessarily endorse any. It is obvious (to me) the Marine Corp zero, is the best. Zero at 36 yards confirm at 300. This puts shots out to 500 into a combat effective (torso) area with no holdover , assuming you are aiming for center mass.

    Of course I could be wrong.
     

    SIG_Fiend

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    "Best" is a matter of circumstances and individual needs IMO. Considering the average citizen would be looking at using a carbine anywhere from home distances to maybe 100yds (neighborhood), they might need a different zero. LE, although typically dealing with different circumstances, might need a zero similar to the average citizen, depending on any number of factors (possibly a more distance oriented zero if they are more rural LE?). Soldiers are a completely different ballgame, and even then, are we talking strictly urban usage, or wide open terrain like Afghanistan? Personally, and it's just my personal preference, I like a 100yd zero. It tends to have about the least deviation from POA to POI through a fairly large range of distances from ~50-200+ (I think as much as ~250yds IIRC) in .223/5.56. So at that point, for most common distances, you only need to know 2 things; hold under at close range, hold basically dead on from ~50-200.
     

    Big Phil

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    I agree on the LE side, however knowing this is the variation aiming at the same point each time I'll take it all day.
    Uploaded with ImageShack.com
    I would assume this kind of grouping is unacceptable for an LE sniper (or any sniper for that matter), having to make extremely accurate shots at varying ranges.

    However in my opinion, I like it.

    This chart is harder to see but it shows varying zeros and impact points. Sorry for the crappy pictures.

    za9apuqy.jpg

    y8u9unu3.jpg
    y4ygapa3.jpg


    Of course arguments can be made for all the different zeros. All of them are pretty good unless of course you need to be really precise. And they will change based on different loads.

    Obviously my guesstimation was wrong on the combat effectiveness.
     
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    benenglish

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    When people have problems with understanding the difference between the bore axis, the line of sight, and the trajectory, I drag out something with sights really high above the bore. Things like this make it easy (well, easier) to explain the fundamentals.
    IMG_0002_zpsf28f3e91.jpg
     
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