280 AI Velocity Validation

Discussion in 'Long Range Hunting & Shooting' started by rodneymoncrief, Mar 6, 2018.

  1. rodneymoncrief

    rodneymoncrief Well-Known Member

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    I have a HS Precision SPL in 280 AI shooting 150 gr. Barnes TTSX using IMR 4831, Quickload stated that my muzzle velocity is 3016 fps. Shooting at 500 yards group was 1 MOA high, also at 600 yards 1 MOA high, both groups were .5 MOA at those ranges. Here's my question, using the Gseven ballistics website it stated my muzzle velocity was an average of 3212 fps, is such a high velocity possible out of a 280 AI using a 150 gr. Barnes TTSX?
     
  2. 30 Hammer

    30 Hammer Well-Known Member

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    Do you have the G7 BC entered correctly? I would shoot it at 300,500 and 700 and gather the drop data from these 3 points as well as your zero range so 4 total points and get your actual MV / BC. I’ve had chronograph makers tell me their machines are perfect and that it’s a BC issue when different and I’ve seen great shooters tell me that the chronograph is not much more than a bore sighting for speed.

    So... shoot drop data to at least 70%
    Of your max range and at at least 3 points and a zero - calculate your MV with a fixed BC.

    Then test to your max range and call it a day.
     
  3. rodneymoncrief

    rodneymoncrief Well-Known Member

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    When I first started shooting 500+ yards I noticed I was shooting 1 MOA high so I thought my zero was off 1 MOA. Checked my zero, right on at 200 yards, checked trajectory using G7 and velocity was 3241 fps, at 500 yards shooting 5 inches high, and 3182 fps at 600 yards shooting 6 inches high which averaged 3212. I'm loading 57.0 grs. IMR 4831 and Quickload shows it should be shooting 3037 fps. I'm just puzzled because 3200 just awfully high for 150 gr. bullet in a 280 AI. Thanks for your input.
     
  4. 30 Hammer

    30 Hammer Well-Known Member

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    Drop data doesn’t lie - that much :).

    I’d go by drop data to 1000. Try to find a sharp angle or two at 350 to 400 and try that with the corrections based off of what you conclude with your drop data and see how that performs.

    Any further and I’d reach out to Brozovich.
     
  5. rodneymoncrief

    rodneymoncrief Well-Known Member

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    I will try that. Thanks
     
  6. dok7mm

    dok7mm Well-Known Member

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    Hodgdon's data for 280 a.i. shows max velocity @ 2910 fps for the 150. I'm shooting 2867 fps, with the 150 Nosler solid base and IMR 7977 in 24" carbon barrel.