7 mm Rem. Ultra Mag Range constants?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by rescurat, Dec 25, 2003.

  1. rescurat

    rescurat Member

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    Just recieved a new rifle and have been trying to find the range constants for figuring windage (minutes of full wind). I have searched the web, and so far come up dry. If anyone can help with either the constants themselves, or a formula for figuring them my self it would be greatly appreciated.
     
  2. DANTEC

    DANTEC Well-Known Member

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  3. Ian M

    Ian M Well-Known Member

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    FULL VALUE WIND ESTIMATION
    Here is one that may be useful. You may have to modify it with field testing but it might provide a starting point.


    1ST digit of range (100's) X Wind Velocity divided by the constant = Minutes of Angle

    Distance Constant
    One hundred to five hundred yards 15
    Six hundred yards 14
    Seven hundred to eight hundred 13
    Nine hundred yards 12
    One thousand yards 11
     
  4. speedbump

    speedbump Well-Known Member

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    Ian's formula is good for a .308/30-06 class of cartridges. A ballistic calculator like the eskimo will get close.

    For my 7mmRUM with a 176 Cauterucio @ 3,360fps, I took a .308 Palma chart (155 Palma loads) and divided the MOA listed by 5. That gets me on paper & close at 1,000 yards. Hope this helps.
     
  5. Michael Eichele

    Michael Eichele Well-Known Member

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    rescurat,

    I am not sure if this would help, but if it does here it is.

    An example for calculating wind would be like this: 3000 (range in feet) divided by muzzle velocity(2600)=1.1538 The real time of flight for standard air density would be (at 1000 yards) 1.7651 useing a 168 grain .308 caliber bullet. Then, 10 miles per hour times inches per second (10x17.6)=176.0 Next take the real time of flight and subtract the time of flight as if there was no apmoshere (1.7651-1.1538)=0.6113 This is the delay time, now multiply the delay time by the inches per second (.6113x176)=107.58 inches at 1000 yards
     
  6. DANTEC

    DANTEC Well-Known Member

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    that seem very difficult to make serious long range shooting without a matched trajectory table and strange because if now we use top fuel caliber in new rifle generation to still want to use Kentuky windage , that enought difficult to read the wind wright to don t add error factor by estimate or use quick formula

    a chart stick on the stock really help and avoid mistake , better is to built a small log book with temp cahrt for elevation ,drop chart and windage chart

    good shooting

    DAN TEC
     
  7. Michael Eichele

    Michael Eichele Well-Known Member

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    DANTEC,

    Im sorry if that is a difficult formula, if I read his post correctly he was looking for a formula as just a place to start.