Is my scope tracking incorrectly or is it "Shooter App"

Discussion in 'Long Range Hunting & Shooting' started by jcann, Sep 30, 2018.

  1. jcann

    jcann Well-Known Member

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    I have a Vortex Razor Gen 1, 5-20x50 and I need your opinion as to if it's not tracking correctly. I'm leaving Oct. 5 for a Colorado antelope hunt.

    First time out after sighting it in I took it to 455 yards. Shooters App gave 2.0 mils elevation. I only needed 1.8 mils on the scope to get on the 10" gong.
    Today I was shooting 910 yards. Shooters App gave 6.1 mils elev. & 1.3 mils wind. I only needed 5.5 mils elev. & 1.2 mils wind to get on the gong.

    If I go into the App and change both the elevation/wind correction factor from 1 to 0.9 I'm almost nuts on to what I observed while shooting in the field.

    Does it sound like my scope isn't tracking correctly. There is no way I can get back out to the field to run a tracking test before we leave.

    I'm shooting:
    7wsm
    180 gr. Berger Hunting VLD
    2920 FPS
    1:8.7 twist
    1.9" scope height
    DA 2920

    Thanks
     
  2. dok7mm

    dok7mm Well-Known Member

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    Adjust your velocity to match your drops. It could be that, or your click value. Pretty simple if it's velocity, in your case adjust velocity up on Shooter until it matches your actual dope. Be aware that a head or tail wind will definitely cause your POI to shift below or above your aim point.
     
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  3. WildRose

    WildRose Well-Known Member

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    Shoot a box test and find out.

    Draw a 12" square and put a bull on each corner.

    Shoot the first.

    Dial down 12moa

    Shooting at the same bull, fire, it should be in the bull direcltly below.

    Dial 12moa left. Shoot the same bull. It should show in the bottom left.

    Dial up 12, shoot again, it should be in the upper left.

    Dial 12 right and repeat, it should be back on the original bull.
     
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  4. dfanonymous

    dfanonymous Well-Known Member

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    It could be a tracking issue. You will have to run a tall target or get a 100 yard mil scale target and test the tracking preferably in a vise.

    However when it comes to ballistic solvers, the issue usually is because people think that they put their information in that it comes out perfect, but that’s not always the case with real work results. So, we true the data to the calculator.
    Wind can effect results and is an entirely a topic of its own.
     
  5. Wlfdg

    Wlfdg Well-Known Member

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  6. Crews

    Crews Well-Known Member

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    The calculator is only as good as the inputs, but it looks like you have a good handle on sight height, environmental conditions, etc. With that being said, it's just a starting point. If you're getting consistent hits that are different from what the calculator is telling you, then you have to believe the bullets.

    So you have to true your calculator with real world dope. I am not familiar with the "correction" factor in that particular app. General consensus is to tweak the muzzle velocity input to match real world dope on targets under 600 yards, and tweak the BC to match real world dope past 800 yards.

    A few other (random) things to consider:
    - are you shooting at an angle? that could be causing the high poi vs calculated value
    - is your zero a true zero? if it's not it could make a big difference at distance
    - are you chambering a new round on a hot chamber and letting it cook for a while before you shoot? you could be getting higher MV than your calculator input.
     
  7. 26Reload

    26Reload Well-Known Member

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    Obviously you are shooting accurately.....
    What speed is the BC of the bullet calculated at from factory..and then what BC is the bullet when you are shooting it at 2920....
    Could easily be the culprit......damn BCs....
     
  8. Crews

    Crews Well-Known Member

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    Exactly! The published BC is only a guideline, and is dependent on velocity. It's not a constant value. As I mentioned above... match calculator outputs to real world results by tweaking muzzle velocity at shorter ranges, and tweaking the BC at 800 and further.
     
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  9. Hondo64d

    Hondo64d Well-Known Member

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    Until you know your scope is tracking correctly, you won’t know why things aren’t matching up. Do a tall target test, checking at least 10 mils or 36 MOA of travel.

    There are several potential points of failure. Your scope may not be tracking correctly. Your muzzle velocity might be a little off. The BC for every bullet will be slightly different from different barrels and could need some minor tweaking. You have to eliminate all of these things. I would start with the scope...

    John
     
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  10. BallisticsGuy

    BallisticsGuy Well-Known Member

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    OP, ping me via PM and I can help walk you through verification of the relevant inputs and do some validation against your app and your actuals. My experience with Vortex scopes suggests click value may not be it but I'll need all your inputs and to do a little Q&A to be sure. We'll find out what's up for sure though.
     
  11. BEEMAN

    BEEMAN Well-Known Member

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    How many rounds through your gun? I needed to adjust shooter app for my 6.5x47 at close to 300 rounds as my barrel picked up speed. Check all inputs again to ensure they are right. Couldn’t figure out a friends 300 RUM a few years ago. Turned out it was his look angle wasn’t set at zero. Just takes one little thing to mess it up.
     
  12. WildRose

    WildRose Well-Known Member

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    Correct, if calculated correctly instead of for marketing hype it's basically an average as the BC actually changes constantly as velocity slows.
     
  13. Bravo 4

    Bravo 4 Well-Known Member

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    The BC would have to go from
    an advertised .659 to closer to .9 G1 to gain (or lose, however you want to look at it) 20” at 910 yards. Your velocity would have to go up over 100 fps, or your scope be off by 10%.
    Which is more likely?
    The .2 mil difference in your drop @ 455 yards is 10% of the 2 mils calculated, and the .6 mil difference @ 910 is 10% as well...I see a pattern here.
    As others have said, check your scope. I check mine in a fixture at exactly 100 measured yards before I ever mount it.
    I’ve had a new (and expensive) name brand scope be off by 10% before. It happens!
    On the flip side, I also have a chronograph that is consistent in spitting out a velocity that seems 100 fps off when I put the numbers in my app.
     
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  14. WildRose

    WildRose Well-Known Member

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    Good point. If the click value indeed proves to be off you can adjust for it in your ballistic calculator.