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Thread: Zeroing Problem. seriously.

  1. #21
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    Quote Originally Posted by wichaka View Post
    I'm running the exact same set up, 6920, ML3 on a LaRue cant mount, and a Troy battle rear.

    Although I have not tried to zero for 25, I had no problem with a 50 yard zero.

    Haven't had an Aimpoint come zeroed out of a box yet. They are close, but not right on.

    Failure2Stop said;
    I generally prefer to zero the irons first with the dot turned off. Then adjust the dot so it sits at the tip of the front sight and confirm by shooting with the dot centered in the optic.


    Yep, what he said..........I find it easier to zero the dot.

    You should be 1 1/4"-1 3/8" low at 25 yards for a 50 yard zero.

    Won't I have to zero the dot even lower the farther i zero to? (this would raiser the barrel up)



    You said "
    You should be 1 1/4"-1 3/8" low at 25 yards for a 50 yard zero"
    My POA correct? or my POI?

  2. #22
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    Quote Originally Posted by ballsout View Post
    Won't I have to zero the dot even lower the farther i zero to? (this would raiser the barrel up)
    Short answer- For your application here- No.
    The long answer is really long, but if you really want to get into it, let me know. Warning- it is really effing boring.

    Do not change your POA (point of aim). Keep the dot/Front Sight Tip on the zeroing target (not both simultanously, of course. Get one zeroed and then shift to the other).

    Adjust your POI (point of impact) to be approximately 1" low (I don't bother with incrimental adjustments at 25 since I will confirm at 50) if you are shooting at 25 yds. If you only have access to a 25 yd range, use wichaka's distances (1 1/4 to 1 3/8) for POI below POA.

    I want POI to be POA at 50 yds, and confirmed.
    Last edited by Failure2Stop; 09-20-08 at 22:30. Reason: name, simultaneous use of sights
    Jack Leuba
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    Knight's Armament Company
    jleuba@knightarmco.com

  3. #23
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    Take off the aimpoint, and work on the irons first.

    Keep turning down the front sight until you get the desired POI @ POA, which will be 1"+ low at 25 yards.

    .........and adjust for windage as you go as well.
    If it isn't durable, it isn't reliable.

  4. #24
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    Ballsout,
    Purchase the Oct issue of SWAT to read about BZOs. Also, you can watch www.downrange.tv/show2 video clips Part 2 & 3. There is also a good sticky in the Optics thread about BZO by LtCol Santose.

    S/F

  5. #25
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    Quote Originally Posted by Failure2Stop View Post
    Short answer- For your application here- No.
    The long answer is really long, but if you really want to get into it, let me know. Warning- it is really effing boring.

    Do not change your POA (point of aim). Keep the dot/Front Sight Tip on the zeroing target (not both simultanously, of course. Get one zeroed and then shift to the other).

    Adjust your POI (point of impact) to be approximately 1" low (I don't bother with incrimental adjustments at 25 since I will confirm at 50) if you are shooting at 25 yds. If you only have access to a 25 yd range, use wichaka's distances (1 1/4 to 1 3/8) for POI below POA.

    I want POI to be POA at 50 yds, and confirmed.
    Do i have this backwards or something? So, I want POI to be 1" low at 25 yards. Won't that mean at 50yards i'll be super low.

    Thanks for working with me on this guys. I feel so lost right now.

    Ok. @ 25 yrds why would i want POI to be 1"+ LOW? Wouldn't that mean the farther the target say... at 50yards the POI will be maybe 3" to low? How is having a POI 1 1/4" LOW @ 25 yards a Zero @ 50yards? Wouldn't POI trying to shoot the 50yrd target be even lower?

  6. #26
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    Quote Originally Posted by ballsout View Post
    Do i have this backwards or something? So, I want POI to be 1" low at 25 yards. Won't that mean at 50yards i'll be super low.

    Thanks for working with me on this guys. I feel so lost right now.
    No. Bullet is still rising between 25 and 50. Hell, at that launch angle, it's rising quite a ways out.

    Difference is, w/50 yd zero, rise angle is shallow compared to a 25 yd zero. There is a significant elevation difference between boresight vs sighting through the irons, upwards of 1.5" IIRC. The shorter the zero range, the more abrupt you have to be in zeroing. When zeroed at 25, the rise angle is so abrupt that at 100 you are several inches high. The 50 yd zero has become a compromise that works pretty well at short range (hold over) and at longer ranges.

  7. #27
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    Quote Originally Posted by jmart View Post
    No. Bullet is still rising between 25 and 50. Hell, at that launch angle, it's rising quite a ways out.

    Difference is, w/50 yd zero, rise angle is shallow compared to a 25 yd zero. There is a significant elevation difference between boresight vs sighting through the irons, upwards of 1.5" IIRC. The shorter the zero range, the more abrupt you have to be in zeroing. When zeroed at 25, the rise angle is so abrupt that at 100 you are several inches high. The 50 yd zero has become a compromise that works pretty well at short range (hold over) and at longer ranges.

    so your saying it appears that my gun shoots low through my iron sights because it has not had enough trajectory to start carrying upwards? Thats why if i zero at 25yards it will mean my bullet will carry to high by the time it hits 50 yards? So that is good that i am hitting low for 25yards when my POI is 1"+ than my POA.

  8. #28
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    Quote Originally Posted by ballsout View Post
    so your saying it appears that my gun shoots low through my iron sights because it has not had enough trajectory to start carrying upwards? Thats why if i zero at 25yards it will mean my bullet will carry to high by the time it hits 50 yards? So that is good that i am hitting low for 25yards when my POI is 1"+ than my POA.
    You're headed in the right direction.

    When you look through your sights, you're forming a perfectly straight line-of-sight from your eye to your target. But, as soon as a bullet leaves the barrel, it starts falling. If your gun was perfectly level with the target, the bullet would never hit where you aimed, always below.

    When you sight in your rifle, you're creating a specific angle between the bore of the barrel and the line of sight through the iron sights or optic. This is providing the trajectory that allows the bullets path to cross the line of sight, and hit the target. The bullet will always cross the line of sight twice -- once on the way up, once on the way back down (Okay, somebody will inevitably feel the need to point out theoretically you could choose a trajectory that met the line of sight exactly at the apex, but that's not very realistic).

    The distance you choose to sight in at will determine both those points where the point of aim (line of sight) and point of impact (bullet trajectory) coincide. So (usually) the goal is to sight in at a distance to create a trajectory that is a flat as possible, and the bullet's point of impact deviates as little as possible from the point of aim over the full flight of the bullet. For an AR, what's typically used is a 50/200 yard zero. If you zero for point of aim = point of impact at 50 yards, you'll be low out to 50 yards, high from 50-200 yards, POA=POI at roughly ( 200 yards, and low past that (drops off pretty fast from there).

    Knowing the trajectory of the 50 yard zero, sighting in so the point of impact is 1" below point of aim at 25 yards, will get you close to POA=POI at 50 yards. So sighting in 1" low at 25 to get start, then fine tuning at 50 is the way to go. Further fine tuning of your zero at 200 yards as Failure2Stop mentioned might be a good step as well, and if you do that, then going back to see how that affected your POA/POI relationship at 50 afterwards is a worthwhile effort also (not necessarily rezeroing, just to check so you know what to expect when shooting at various ranges). Of course it's not a must, and if you don't have a 200 yard yard range don't worry about it. Me, I'm not sure I can see good enough at 200 yards to do anything but frustrate myself.

    Follow what these guys have been saying to get zeroed at 50 yards. Do it with the Aimpoint and irons separately. Don't worry too much about how the red dot and irons intersect with one another as long as you can use them both on their own.
    --Josh H.
    Zombies seek out and eat brains. Don't worry; you'll be safe if they attack.

  9. #29
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    Can't thank you guys enough.... Thank you for you time and hospitality.

  10. #30
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    Here are some simple charts to help illustrate what jamrt and LOKNLOD
    were saying about the ballistic flight path.

    Link1
    Link2

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