ERL Ballistics 'Truing' help

Discussion in 'Extreme Long Range Hunting & Shooting (ELR)' started by BigBboy25, Jun 24, 2012.

  1. BigBboy25

    BigBboy25 Well-Known Member

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    I went out today with my .300 Win. Mag. and a bunch of 210 Berger VLD's loaded up to practice a little bit. The rifle shoots very well and I've had great success with this load. The first shot I took was:

    1,080 yards
    Temp. 76 F
    Barometric Pressure 24.48 in Hg
    Humidity 13 percent
    Angle +3.4 degrees
    Latitude 39.45, azimuth 57 degrees
    KAC Bullet flight called for 23.25 MOA and no wind. First shot drilled the milk jug.

    Next shot was 1,139 yards on one gallon milk jug
    Temp 84 F
    Barometric Pressure 24.48 in Hg
    Humidity 13 percent
    Angle +4.0 degrees
    Latitude 39.45, azimuth 30 degrees
    KAC Bullet flight called for 25.25 MOA and 1.75 MOA for 4 mph full value wind wind. First shot was about 0.75 MOA high, 1/4 MOA right. corrected and fired second round and clipped the right side of the jug and rolled it down the hill.

    I decided to try one more shot and it was at 1,555 yards on a little bigger than basketball sized rock.
    Temp 84 F
    Barometric Pressure 24.48 in Hg
    Humidity 13 percent
    Angle +5.6 degrees
    Latitude 39.45, azimuth 27 degrees
    KAC Bullet flight called for 43.25 MOA and 2.5 MOA for 4 mph full value wind wind. First shot was called 3.5 MOA low, good for wind. corrected and fired second round and hit the base of the rock.

    I was wondering if anyone had suggestions on how to true my ballistics calculator a bit better. It is spot on out to about 1,100 yards and then I start having errors. I have chronographed my load extensively and I'm confident in my MV and ES is in the 12-15 fps range. I'm getting atmospherics from a Kestrel 4500, measuring range with both a Bushnell 1500 and Leupold RX-IV rangefinder. I have a Leupold VX-III and have checked the tracking on it and have inputted the correction factor into the program. I am also running a single G7 BC of 0.323. If anybody has any ideas on what to try to help bring the output of this program more in line with the results I'm getting? Thanks in advance for any advice.
     
  2. Eaglet

    Eaglet Well-Known Member

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    What's your average Muzzle Velocity?

    What distance did you zero in for?

    What is your scope height?

    Do you have info for your zero condition?

    When you zeroed it in, was the angle slope 0°?
     

  3. royinidaho

    royinidaho Writers Guild

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    Eaglet is asking the right questions!
     
  4. BigBboy25

    BigBboy25 Well-Known Member

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    MV- 2940 measured by Chronograph at 15'. Was 38 degrees F outside when chronographed, load is with H1000. 2970 fps input into program which trued program to 1000 on paper well.

    Zero range - 202 yards

    Scope height - 2.045" center of bore to center of objective

    Zero input conditions - Yes, all zero conditions taken from Kestral and inputted directly into program. Angle of slope was measured at 2 degrees uphill.

    Did I get them all?
     
  5. Eaglet

    Eaglet Well-Known Member

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    I'm trying to get info from you to see if I can get the same numbers you're getting.
    When you zeroed the gun, it seems to me it was done on a different day.
    If that's so, I would like to get those values... to input them as zero conditions and
    use the other ones you have already given us as "field condition".

    Did you re-zero on this day?
    Thanks...
     
  6. BigBboy25

    BigBboy25 Well-Known Member

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    Eaglet, I appreciate your help with my frustrations. Below is the 'Zeroing conditions' copied directly from my ballistics program. I did not rezero on the day I fired the shots mentioned above. I've never had my zero wander on my scope, but maybe I should have checked that though.

    MV - 2970fps
    Zero Range - 202 yards (Not high or low of aim point thus no Y-intercept was needed)
    Sight Height - 2.045"
    Temp - 87 degrees F
    Station Pressure - 24.50 inHg
    Angle - 2 degrees uphill
    RH - 30 percent
    Altitude - 0 ft (This is required of my program when station pressure is used)
    G7 BC - 0.323 lb/in^2
     
  7. Eaglet

    Eaglet Well-Known Member

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    My advice is like this:
    If you're zeroed at 202 yd, place vertical targets at 500 yd, 800 yd and 1200 yd. Shoot at least 3 shot group to each after adjusting for vertical elevation
    according to your program. Measure from the center of the group so see what
    adjustment you'll need for each. Of course the 202 will not need adjustment.
    Then, since you're pretty sure about your muzzle velocity, then make small adjustments
    to the BC until it matches the values that it should have.
    For example, let's say the program says for 1000 yd you need to go
    up 23 MOA but the 3 carefully taken shots measure 9" high so...
    9/1.047/10 = 0.8 MOA from center of the 3 carefully taken shots. Then you make
    small adjustments until your app says 22.2 MOA up. Hopefully those small adjustments will allow you to get to a point very close to all distances being pretty
    close.

    Some folks are fully sold on Litz's G7 BC and they make adjustments on the muzzle velocity until you get as close of a match as possible. Others, adjust the BC
    ad others adjust both which I don't think is such a good idea.

    In any event you have a pretty good idea of how to go about it.

    NOTE: I'm taking for granted that the rifle and the shooter are capable to hold small groups at all distances. :)
     
  8. bigngreen

    bigngreen Well-Known Member

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    What value is your scope tracking at?
     
  9. BigBboy25

    BigBboy25 Well-Known Member

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    Thanks for the advice Eaglet! I did a similar thing by shooting groups at 600, 800, and 1000 and that's how I came up with using 2,970 fps in the program. I also appreciate the benefit of the doubt on the group size! :D I'm going to take your advice and set up a target frame at 1,200 and shoot a few groups and see how things go. As far as how my scope tracks, I tested it for 30 MOA using a tall target test at 100 yards and it was giving me 1 percent error. This could also be contributing to some issues at longer ranges, and I don't know if my scope has tracking issues at the end of it's adjustment range. I've got some testing to do for sure. Thanks for your help guys!
     
  10. Ring

    Ring Well-Known Member

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    "Truing" your ballistic software

    “Lowlight”
    You can calibrate most software and is simple enough too do.
    Some of the elements in the video “Magpul” are correct for other software, like actually shooting to a range that puts the round around 1300fps. (example)
    The steps are simple enough, calibrate your scope and if necessary adjust the software using the sight offset, click value, etc. This will work with most software to include the iPhone Apps.
    Then, calculate actual drop. You can start at 300 yards to begin. At this range you can adjust your BC if necessary. The BC will move based on the rifle shooting it. For example BulletFlight has an option in the utilities area to adjust BC based on Drop. it will give you a new G1 or G7 which you can then input into your data section.
    Lastly you can calibrate the drop out to 800 yards like the video. Checking at distance is the final step, but you should have at least choreographed your load to start with, if you haven't then some software does have functions to adjust it based on drop.
    Certain software has a DK function to bend the curve, this is used in place of adjusting the BC or MV, so you can do it a number of ways with a number of different software solutions, not just the Horus. Remember he was hired by Horus in the beginning to work and sell Horus methods and products, so of course they are not going to inform you of other methods.
    Calibrating the system like above I have taken software like Field Firing Solutions and Patagonia LB3 out to distances beyond 2000 yards with very successful hit rates. Inside 1500m the first round hits where more consistent than when you didn't do it, and at 1000 yards and in it was too easy with a rifle like a 338LM.
    The system calibration should be:
    1. Muzzle Velocity using a chronograph
    2. Scope calibration to at least 48"
    3. Drop to 300 yards to tune with then
    4. Drop to to 800 yards to fine tune.
     
  11. BigBboy25

    BigBboy25 Well-Known Member

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    Thank you ring! I really appreciate it!