How to calculate 0 @ 100 from one load to another?

Discussion in 'Long Range Hunting & Shooting' started by Wallythe7mmWeatherby, Mar 6, 2018.

  1. Wallythe7mmWeatherby

    Wallythe7mmWeatherby Member

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    Curious here, is there anyway to calculate a zero with a ballistics app from load A to load B? Or do you just have to re-shoot and zero it again each time you switch ammo?

    Ex: If I go from shooting Federal 160 gr nosler partitions @2950 and a BC of .475 from my 7mm, to shooting cheaper Federal 150 gr soft points @3150 and .359 BC while with friends. Is there any way to know what my moa shift should be from one to another? And to use that offset when dialing in a solution to hit some 300 yard gongs for just fun?

    Or do I just have to leave my sight on my preferred as a zero, take some test shots, and record what the difference is and remember/make a note of that?
     
  2. Bravo 4

    Bravo 4 Well-Known Member

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    You can never guess how one load’s point of impact (POI) is going to be. After you zero for one load, shoot the other and annotate POI difference. Then make said correction for the new load and then switch back after shooting so you are back to zero for your original load.
    We do this all the time, zero with our LR/match ammo then keep track of how M80 ball ammo shoots in case ya got to de-link some M240B ammo. Make a quick adjustment for the ball ammo and use the reticle in the scope for hold-over and hold-offs. Keep another set of data for it.
    Or you might get lucky and both loads shoot to the same POI.
     
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  3. dok7mm

    dok7mm Well-Known Member

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    Being there won't be a great difference @ 100 yds, you can set up your main load zero under it's name in the app. Then set up your second bullet choice and enter the zero using the offset feature for any difference in elevation and windage.

    Or you can enter one rifle name and enter two load names.

    Either should work, unless I have confused myself. :D
     
  4. Crews

    Crews Well-Known Member

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    There is obviously no way to calculate what your change in POI will be within a ballistic calculator. That is just silly.

    However..... if you determine what the POI shift is at 100 yards, it can be accounted for in a ballistic calculator very easily. Most calculators have an input titled elevation offset and windage offset. Keep the same scope zero, just create a new profile for the different ammo, and enter the values for the POI shift into the offset section. that's exactly what it was designed for.
     
  5. dok7mm

    dok7mm Well-Known Member

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    I think that's what I said, or tried to say.
     
  6. LastShot300

    LastShot300 Well-Known Member

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    +100
     
  7. gohring3006

    gohring3006 Well-Known Member

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    Re zero and record turret data in your data book.
     
  8. Crews

    Crews Well-Known Member

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    no. Did you not read what I just wrote about zero offset? There is absolutely no need to re-zero anything.
     
  9. gohring3006

    gohring3006 Well-Known Member

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    No, I didn’t read that.
    If you have two loads with different impacts. Why can you record the clicks on your data book that it took to zero your second load?
    It doesn’t matter now, I really don’t care.
    Just seen you are not the OP any way. I basically am saying the same thing as Bravo.
     
  10. Bravo 4

    Bravo 4 Well-Known Member

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    Yep, two ways to skin a cat...old(ish) school and new style. Even if you are using an app you should still be keeping track of your dope. The offset ballistic calculator function is great, but electronics are prone to failure. Then what do you do? My phone (w/ballistic app) got so cold this past season, after just a few minutes being exposed, that it shut down until I rubber banded (is that a word?) a hot hands to it and left it in my inside coat pocket for a while.
    Use both methods...
    The two load technique isn’t just for the range, I know guys that have two loads for their hunting rifle; a well constructed or bonded bullet for close shots and a higher BC more rapidly expanding one for long range.
    I’ve been considering this as my experience with an elk at 40 yards and 300 grain Bergers out of a RUM case were less than desirable. Been looking at the Sledge Hammers for closer work and staying with the Berger for several hundred yards and out.
     
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  11. gohring3006

    gohring3006 Well-Known Member

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    I agree, I use my app for drop data within my current weather conditions. Two of my rifles, I have documented every shot I ever took with them.