Could this be right?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by J300UM, Feb 14, 2012.

  1. J300UM

    J300UM Well-Known Member

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    I took my chrony out the other day to let my buddy shoot his 6.5-06 AI over it to check his velocities (averaged just under 3300). Afterward we zeroed the rifle at 200 yds and also shot it at 600 yds. I dont have my notes in front of me right now and don't remember the adjustment off the top of my head. Once we got it on at 600 yards, I went back to the house and entered the information in the Gseven program and came up with a G1 b.c. of .606! This seems extremely high for a bullet of this caliber and weight. I've read in several forums that the claimed b.c. of the 6.5 hornady sst and interbond were way underrated but to this extent? I was just curious what kind of numbers some of you guys with experience with these bullets were coming up with. I keep thinking I had to have entered something wrong in the program cuz .606 seems almost too good to be true...
     
  2. Stormrider

    Stormrider Well-Known Member

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    You didn't tell us which bullet you were shooting...
     

  3. J300UM

    J300UM Well-Known Member

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    Oops...no I didn't did I... He is shooting the 6.5mm 129gr Interbond.
     
  4. ZSteinle

    ZSteinle Well-Known Member

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    129 SST BC is .483 so i would be doubtful the interbond is much better if any.
     
  5. brentc

    brentc Well-Known Member

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    I believe they are both pretty close, but I also believe they are both underrated at .483.

    To the OP, can you confirm that your velocity is correct?
     
  6. J300UM

    J300UM Well-Known Member

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    I had to have entered something wrong the first time. I went through all my data and ran the numbers again last night and came up with a G1 value of .505. Seems much more realistic to me. That's not too shabby for a 129 gr slug. I may give em a try in my .264wm when I get my scope. Looking at the numbers, it should outrun the 140 gr Accubond with a claimed B.C. of .509 (which has been stated by some to be overinflated).
     
  7. Tikkamike

    Tikkamike Well-Known Member

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    more than likely your velocity reading is low which means your bc must be boosted to match your drops. thats why it looks like the BC is so high.
     
  8. J300UM

    J300UM Well-Known Member

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    I want to shoot it over another chrony to see if it's any different than mine. I have suspected mine to be off from time to time but have never been able to verify it against another one. I'm kinda hoping LTLR will chime in on this one. He had a thread a few days ago shooting the 129 sst and made mention that the b.c. of that bullet was underrated. I would like to see how close his figures are to mine...
     
  9. ZSteinle

    ZSteinle Well-Known Member

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    That is the average across a wide velocity range

    3000fps is .520
    2500fps is .499
    2000fps is .481
    1500fps is .430

    so i would guess that over 600 yards your bc calculation is spot on of .505