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  • Frustrating Ballistics Solution Problem

    I'm shooting the new hornady 147gr ELDM in my rifle and the first time I shot the load I was consistently low 0.5mil at 4-600 yds from what my ballistics calculators told me. I've verified my zero, calibrated my scope turret correction factor (SWFA SS 3-15 FFP), chronographed my loads at 2758fps (V3 magneto speed), and meticulously verified all of my inputs. I'm doing the same thing I do for every one of my guns and I haven't had this problem. At such a short range, I can't think of anything that would cause that kind of error.

    I thought maybe the difference was shooting prone in grass to zero and concrete to shoot. I verified that this has no affect on poi. The gun shoots 1/2-3/4moa and the 0.5mil error is repeatable and consistent. The scope tracks well and returned to zero after calibration to 14mils.

    4 separate ballistics programs agree the solution is 3.6mils at 610 yards but I had to dial 4.1 to hit the target; I needed 2.5mils at 423 yards when the computer says 2.0.

    What am I doing wrong?

  • #26
    It would be odd but it's about the only thing left I can think of.

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    • #27
      Your Rifle cannot match your software, you have to match your software to the rifle, that means truing.

      The computer assumes a lot, it has not idea about you the shooter, which has a huge influence.

      It only knows what you tell it as far as zero range, the true zero range might not be, 100 yards like you think, you can adjust that. Same with the BC, it might not be what is advertised because you are pushing it too slow or spinning it different than they did when they figured it. You can adjust these factors for your system

      Depending on the software it will add and subtract things you might not realize, and turning on all the options might be hurting your results

      The rifle system, which includes, Rifle, Scope, Shooter, Ammunition is correct, your software is not
      Last edited by SHLowlight; 08-09-2017, 03:58 PM.
      Lowlight

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      • #28
        I shot a scope tracking drill today, see picture below (ignore crap group on 2 mil line). Seems to be tracking correctly but in doing so I noticed something odd. The poi shifted 0.2 down and 0.2 right.

        I zeroed the last time I shot and now I'm off the amount I had to shift my zero last time. My loads were made up from a mix of new unfired brass and 2x fired brass. Is it possible that these different loads are causing a diff poi shift?

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        • #29
          Did you rezero and record your atmospherics?
          Last edited by TacticalDillhole; 08-11-2017, 06:29 PM.
          The lyf so short, the craft so long to lerne
          "Do not pray for an easy life, acquire the strength to endure a difficult one" -Bruce Lee

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          • #30
            No, I'm going to prep all my brass the same and then rezero and record all my info. Running low on H4350 and I have to save enough for an upcoming match so I'm being very stingy with my shots.

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            • #31
              Zeroed today and shot a group at 270yds (longest I have) without dialing any correction on my scope. See the pics for the results. With a confirmed zero the solution was 0.9mils and I measured a drop of 0.89mils so it appears my problem is solved, at least to 270yds.

              We'll see what happens in my match but I guess the new unsized brass was causing a poi shift?

              Comment


              • #32
                Originally posted by gilk View Post
                Zeroed today and shot a group at 270yds (longest I have) without dialing any correction on my scope. See the pics for the results. With a confirmed zero the solution was 0.9mils and I measured a drop of 0.89mils so it appears my problem is solved, at least to 270yds.

                We'll see what happens in my match but I guess the new unsized brass was causing a poi shift?
                So if you update AB with your zero atmosphere and then go to the solution and put in the atmospherics of where you were shooting with the original problem, what does it look like?
                The lyf so short, the craft so long to lerne
                "Do not pray for an easy life, acquire the strength to endure a difficult one" -Bruce Lee

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                • #33
                  Exactly the same, 3.6 mils. That atmospherics don't make anymore than 0.1mil difference at that range.

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                  • #34
                    Had a slightly similar thing come up with a rifle/load in FFS.

                    Assuming you have a good zero and atmospherics, start reducing your input BC until you hit where your target is at distance with a known 100y zero. Chances are it will be on at longer ranges and you're set. Listed BC from bullet manufacturers is rarely the correct BC.

                    Also make sure there is absolutely no parallax as well as you are not shooting up or downhill by more than 10 degrees (if you are, a cosign adjustment may be a small part of where you are off)
                    10. Panzerdivision - 23. Gebirgsjäger 'Bayern'
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                    • #35
                      Originally posted by TheGerman View Post
                      Had a slightly similar thing come up with a rifle/load in FFS.

                      Assuming you have a good zero and atmospherics, start reducing your input BC until you hit where your target is at distance with a known 100y zero. Chances are it will be on at longer ranges and you're set. Listed BC from bullet manufacturers is rarely the correct BC.

                      Also make sure there is absolutely no parallax as well as you are not shooting up or downhill by more than 10 degrees (if you are, a cosign adjustment may be a small part of where you are off)
                      The published BC is only valid at the given MV since velocity is a factor in the drag coefficient which is a factor in the coefficient of form. So unless your MV is exactly what is advertised on the box, the BC isn't 100%
                      The lyf so short, the craft so long to lerne
                      "Do not pray for an easy life, acquire the strength to endure a difficult one" -Bruce Lee

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