Reverse calculating software

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by joel0407, Mar 14, 2009.

  1. joel0407

    joel0407 Well-Known Member

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    Is there any Ballistic software that will reverse calulate.

    If I enter my B.C. and Velocity and then go out to to range and shoot it to 500m. If I get a different drop at 500m I want to just enter that figure and have the software recalculate drop values at the intermediate distances.
     
  2. Michael Eichele

    Michael Eichele Well-Known Member

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    The easiest and most reliable way is to change the BC in the BC field in the software untill your computer matches your real drops. This is your real BC. It is typically different from published BC's.
     

  3. Eaglet

    Eaglet Well-Known Member

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    Good answer, meichele! +2
     
  4. joel0407

    joel0407 Well-Known Member

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    Thanks people.

    I was thinking there maybe software that I could enter muzzle velocity, zero 100m and drop at 500m and then it would adjust B.C. automatically.
     
  5. jwp475

    jwp475 Well-Known Member

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    Exbal has the "Trajectory Validation" feature. shot your 500 yard target with the drops given if the POI is different then enter that number at 500 yards and Exbal will do the rest

    Example if at 500 yards your drops are 3" lower than predicted enter -3" in the trajectory validation feature and the program will do the rest.
     
  6. Eaglet

    Eaglet Well-Known Member

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    Will do the rest, meaning it will adjust the muzzle velocity to what velocity would be needed for the bullet to have dropped that many inches at whatever distance. So by adjusting the muzzle velocity instead of the BC it gets away with it. It's important though to remember that adjusting your BC is what will give you more accurate adjustments that will match your true bullet trajectory much closer specially at longer distances.
     
  7. jwp475

    jwp475 Well-Known Member

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    It's also important to have the proper muzzle velocity. I had this problem at 975 yards. I chronographed the 3338 Lapua and came up with 2820 FPS and I was consistently low at 975 yards I played with the BC a bit and was not getting satisfactory results. So I decided to recheck my zero and to rechronograph my load at the same time. This time I got 2791 FPS average and the problem was solved. Of course the programs trajectory validation had alredy predicted as much and I have no issues with my drops since. Just my experience..


    [​IMG]
     
  8. joel0407

    joel0407 Well-Known Member

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    Sweet

    I want to do that with the 300rum
     
  9. Eaglet

    Eaglet Well-Known Member

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    jwp475,

    and that's an awesome experience! I can't argue with that. Once the BC for your particular weapon has been established and the bullet impact is not on, then is time to check our muzzle velocity. Exbal will definitely help you big time with that!


    The point I'm still trying to make is the need to obtain the right BC for whatever we're shooting. Changing MV (without the properly adjusted BC) will only be a temporary solution for the problem; will shoot on target at that particular distance and when you change distances then you got to do it again. On the other hand, if the right BC has already been established and due to temperature changes we have a different MV then using Exbal like that will give you a good permanet solution for a range of distances until that MV changes again and or the established BC needs some tweeking.

    Good posting and good experience!
     
  10. jwp475

    jwp475 Well-Known Member

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    +1.. Spot on
     
  11. joel0407

    joel0407 Well-Known Member

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    Thanks for your help fellas. I think I'm going to order a copy of Exbal.
     
  12. DropDead

    DropDead Well-Known Member

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    Adjusting muzzle velocity from actual recorded velocity to get drop data will directly effect your energy data.
    By adjusting your b.c. instead and using actual recorded muzzle velocity your energy data will be much more accurate.
    Just another plus for using actual recorded muzzle velocity.

    My 2 cents.
     
  13. LouBoyd

    LouBoyd Well-Known Member

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    Becides the muzzle velocity and drop make sure you've got the correect sight height over the bore and the correct atmospheric information entered into your computer program. Otherwise yoiur new adjusted BCs will be meaningless and yoiu're data won't be right if you change sights or the weather changes.
     
  14. cdoubleu

    cdoubleu Member

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    If you're willing to spend $300 on software for a PDA/Pocket PC, Horus Vision's AtragMX does exactly what you are asking for. BC is dynamic, so it does change throughout the bullet's flight based on velocity. A big problem is everyone uses the G1 (C1) ballistic model to compare all BCs. The G7 model is designed for long caliber, boat tail bullets and matches the curve associated with the long, slender, efficient bullets used for long range shooting, unfortunatly, it doesn't compare proportionally to the G1, and is a much smaller number, so to make a bullet look good manufactures use the G1 coefficient. AtragMX allows for input of multiple G1 BCs along the flight, and the software will even calculate it from empirical drop data gained from your rifle. I love their product, but without accurate environmental and range inputs, crap in=crap out. So get yourself a kestrel 3500 or higher model and good LRF while you are at it if you don't already own them. To solve your velocity problems: Many powders are temperature sensitive. Temperature changes the burn rate, which effects muzzle velocity. AtragMX will also keep track of different velocities for different temperatures, eliminating this problem. So you will want to test the velocity of your loads for different ambient temps and record your average. I have no affiliation with Horus Vision other than being a satisfied customer with their products.... I only wish their customer service was better.