270 Win 100 yd zero

Discussion in 'Long Range Hunting & Shooting' started by TannerGun, Sep 26, 2011.

  1. TannerGun

    TannerGun Well-Known Member

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    Hey fellas, zeroed my little 270 in this morning. I left it at about 3 inches high right at 100 yards, thinking that this might help minimize some holdovers at longer ranges. Can anyone kind of break it down as far as how much this might decrease holdover? Or should I just knock my zero down to 2 inches high?

    BTW, shooting a 130 BT at an estimated 3250 fps, 26 inch barrel+ 63.5 gr of Magpro.
     
  2. Dr. Vette

    Dr. Vette Well-Known Member

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    You're much better off verifying the zero at 200 yards and beyond. I've had rifles that I set 2 inches high at 100 that go to 6 inches high at 200 though I haven't touched a thing. Why? I don't know, but I don't trust the 100 yard zero without verifying beyond that.
     

  3. backwoods83

    backwoods83 Well-Known Member

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    All my rifles that are not bench guns are set dead on at 100yrds from there I use mildots for the ones that have them but for the others I adjust the crosshair as needed but I do not reccomend doing this with el cheapo optics as they may not track back like they should, but this is the best way, and I think your load is likely closer to 3160 +or- 20fps.
     
  4. TannerGun

    TannerGun Well-Known Member

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    I'm definitely going to check at 200. Shooting at 415 I hold directly on. And I'm pretty comfortable in stating that my load is running over 3200 fps, my barrel is longer than what Accurate used in testing Magpro, and knocked down from their max by just 1.5 grains
     
  5. BuckSnort

    BuckSnort Well-Known Member

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  6. WildRose

    WildRose Well-Known Member

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    That would put you pretty close to a 285yd zero.

    Ballistics Calculator v1.0

    I find their ballistic calculator very handy.

    Ballistics Calculator - Hornady Manufacturing, Inc
     
  7. WildRose

    WildRose Well-Known Member

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    If you are dead zeroed for 415 with that your numbers need to be adjusted.

    What BC bullet are you using?
     
  8. CogburnR

    CogburnR Well-Known Member

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    A 3 inch zero at 100 is good but check it at 300 and zero it there.

    Keep in mind that your midrange trajectory will be at around 175 yards and 4" high. That is about as high as you want it! The midrange trajectory being high has caused many misses from shootovers.

    Magpro may get you close to that speed but if you chrony it at actual hunting temp you might find it is slower than you think.

    I just shot some 130g sierra's in my 270 wsm with a 70g charge of Magpro and it was 3230 until the barrel warmed a little then it was over 3300. It went from a low of 3232 cold to 3345 with a hot barrel(shot 5).
     
  9. TannerGun

    TannerGun Well-Known Member

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    I guess saying that I.hold dead on at 415 was misleading. I was shooting at a 12 inch piece of steel, holding right on the top and hitting the middle, so I was wrong. Sorry about that. I have no idea what the BC of the 130 NBT is. I'm hoping that Magpro isn't TOO temp sensitive.
     
  10. Bravo 4

    Bravo 4 Well-Known Member

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    .433 BC for the 130 NBT. What these guys are trying to tell you is to punch your numbers into one of the ballistic calculators. The problem is you don't have any specifics, just some guestimates so it won't be as accurate... You need to go burn some powder and get some actual drop data.
     
  11. WildRose

    WildRose Well-Known Member

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    Yep. Chrono so you know what your real velocity is.

    Then three shot groups at 200, 400, 600 to get your actual drops.

    Then using any of the good ballistic calculators out there you can adjust the BC to get accurate drops for all ranges you plug into the calculator.
     
  12. silvertip-co

    silvertip-co Well-Known Member

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    3" hi @ 100y is perfect for 270. Youll be dead on at 300. At 425 ( my range only goes to 425) youll be mebbe 8 inches low. Good job.