Need a little technical help

Discussion in 'Long Range Hunting & Shooting' started by loosesniper2000, Oct 10, 2010.

  1. loosesniper2000

    loosesniper2000 Well-Known Member

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    Here's the scoop. I shoot every week past 1000 yards but lately I'm having a little trouble getting things figured out. Here's the situation I'm having.
    I use the Nightforce software and put in the correct info concerning pressure, temp, altitude, scope height humidity and so on. My velocities were checked using 2 different chronographs (ced and pact) everything is entered right but when I shot at 1200 yards tonight my shot is consistantly 2 moa off. (high) This is happening every week and no matter how many times I double check things it's always off.
    If you know a solution I'm all for it. I am using several different guns and get the same consistencies.
    Thanks for any help, Dustin
     
    Last edited: Oct 11, 2010
  2. loosesniper2000

    loosesniper2000 Well-Known Member

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    Any suggestions?
     

  3. partisan1911

    partisan1911 Well-Known Member

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    Has it alway been 2moa off at that range? Maybe the bc isn't being calculated correctly in the ballistics program? Or even a lot change in your bullets?
     
  4. Oliveralan

    Oliveralan Well-Known Member

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    are you adjusting for the magnus effect? are you also high at different yardages or only 1200? or is it less at shorter yardages?
     
  5. loosesniper2000

    loosesniper2000 Well-Known Member

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    I adjusted for spin drift but the magnus effect I don't believe is on the software. If it is please let me know. As for the distance it's at other ranges as well. I would say it starts to differentiate about 800 yds.
    It's really bugging me I can't figure this thing out. I'll try another chronograph but I doubt that will help. I actually experimented with changing the B.C and it works out perfect. I know there's got to be something I'm missing. I know the magnus effect is a force perpendicular to the line of motion, but that usually equates to a horizontal drift.
    I appreciate the feedback, but still let me know where the option is to check this.
    Thanks
     
  6. loosesniper2000

    loosesniper2000 Well-Known Member

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    I'm using the JLK 7mm vld bullets in one of my STW's They said the bc was .690 and I'm shooting at 1460 altitude. I really don't know how to tell if the bc is calculated correctly.
    I'd be fine if it was one bullet but I'm also experiencing it with 3 other guns
     
  7. Oliveralan

    Oliveralan Well-Known Member

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    Magnus affect is about 15% of your windage. A right hand wind (assuming right hand twist bbl) means your bullet will impact high by around 15% of your windage (exact percentage varies with twist rate, muzzle velocity and a lot of others but 15% should get you very, very close).

    If you have a predominant right hand wind, that would explain why you shots are. However 2mins is a lot, you would have to have dialed a LOT of windage

    also, what is the terrain like? You could very well be shooting through an upwards wind. That would raise impact.
     
  8. loosesniper2000

    loosesniper2000 Well-Known Member

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    My guess is I'm shooting in an upward wind. I get the same results when there's no wind as well as a 3-9 or 9-3 crosswind.
    I live in a valley and the wind is brutal, I'm usually shooting perpendicular to the wind but when I shoot parallel with it I notice my shots are much closer.
    I went from 2moa high last night shooting perpendicular at 1240 yds and then turned right into the wind (little at that time) and shot at 1260yds and my adjustments worked out nearly perfect. So I guess it is the upward cycle that's screwing me up....I think