300 RUM ballistic issues

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by jwhunter, Oct 25, 2018.

  1. jwhunter

    jwhunter Well-Known Member

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    Got a quick question for you guys.
    Got my load development done on my custom 300 RUM. Chronoed with the magneto speed and running the strelok pro app. It was telling me to hold for 7.3 moa at 500 but was shooting high and got it centered at 5.0 moa. Had to just my fps by almost 300 fps which shouldn't be right. But at 1000 shooting way low. Can't figured out what's going on and driving myself crazy. Curious what you guys think. BC, scope height all looks good.
    Thanks guys!
     
  2. WeiserBucks

    WeiserBucks Well-Known Member

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    Bullet stability?
     
  3. gohring3006

    gohring3006 Well-Known Member

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    Double check all your inputs. 9 out of 10 times when that happens it’s the inputs.
    Atmosphere, scope height, etc.
    What bullet are you using?
     
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  4. jwhunter

    jwhunter Well-Known Member

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    I'm using Berger 210s (.625 BC). I'm shooting 87gr H1000 and the magneto is reading 3007 fps. It was telling me to hold 15.5 moa which is way too short. I was hitting 1000 with 19.75 moa which makes sense to me.
     
  5. Gord0

    Gord0 Well-Known Member

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    This. 100%
     
  6. gohring3006

    gohring3006 Well-Known Member

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    Are you sure you have your drag model set at G1 BC?
     
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  7. lancetkenyon

    lancetkenyon Well-Known Member

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    Has to be your inputs.

    Although I have found much more accurate results from Shooter over Strleok Pro (I have both).

    I would re-input all your data, then go shoot multiple ranges and true everything up.
     
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  8. Wachsmann

    Wachsmann Well-Known Member

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    When you say you have it centered at 5MOA is that what you have your zero point set to or were you saying you were 5MOA high when you were shooting at 500 with the 7.3moa dial up? Example 5MOA high at 100 yards. If so then this needs to be taken into account as well. In my experience its been the way I have input my data. I use shooter and its pretty much been spot on out to 1200 yards for me. I haven't shot out past this with good results but that part is my hand loads and semi factory setup.
     
  9. BallisticsGuy

    BallisticsGuy Well-Known Member

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    Ok, you're all messed up. PM me with your inputs and I'll get you sorted. It's kinda my thang.
     
  10. jwhunter

    jwhunter Well-Known Member

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    I'm using G1 (.625). G7 is .320.
    Sorry what I meant is after my inputs it told me to hold 7.3 moa at 500 but it was too high (10 inches). I had to back it down to 5 moa before I was hitting center. I imagine it's my inputs and have to double check everything. Thank you BallisticsGuy. I'll PM you tomorrow. Thank you everyone for your inputs!
     
  11. gohring3006

    gohring3006 Well-Known Member

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    I was implying that you could be putting your g1 BC into your program and you might have it on the g7 profile. I’ve actually done that before.
     
  12. BallisticsGuy

    BallisticsGuy Well-Known Member

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    I'm working the problem for our guy now. I've done a bunch of tweaking on his inputs looking for the issue. Right now there's a suspected cause that I'm fairly confident in but that's pending verification with some more info from jwhunter. We'll get him sorted. There's always a reason.
     
  13. Monkeywerench1973

    Monkeywerench1973 Member

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    I have same problem chrono said 3033 FPS at 59temp 2000ft 1.8 twist 7mm 180 Berger vld hunting 29 pressure 30 humitady scope 2 inch high out of 28nosler at 600 yards it has me shooting 7 inch high when I change the FPS on the chart to 3150 I’m 1 inch inch low 8 moa has me hitting and the bc is .673 what am I doing wrong
     
  14. BallisticsGuy

    BallisticsGuy Well-Known Member

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    Monkeywerench: I get 9.7MOA for 600 with that load at 2k ft altitude at 60F. Keep in mind your zero not being 100% spot on will affect you at long range. You're ~1MOA off so I suspect your zero isn't perfect and / or your calculator doesn't like you using both barometric pressure and elevation. Some applications set that as an either/or.

    If your zero is off at 100yrds by .5" then you'll see exactly what you're seeing now at 600yrds, within the cone of uncertainty formed by group size, shooter error and shot-to-shot MV variation so that's where my money is at. Everyone thinks their zero is dead nuts but very few people actually do get it dead nuts.

    I've run several simulations and the above seems like your best answer Monkey. Feel free to PM me if you want to get into the weeds troubleshooting. I'll help you out.