Trajectory Question

Discussion in 'Reloading' started by ShortMag3, Mar 6, 2011.

  1. ShortMag3

    ShortMag3 Well-Known Member

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    Why would a 178 AMAX at 2460 FPS from a 24" AR10 barrel hit the target 6" higher than a 168gr cheap ammo at 2600fps?
    This happened at the range yesterday with a friends rifle. We chronographed both loads and the Amax was slower but hight much higher.

    Thanks for any answers

    ShortMag3
     
  2. BigSkyGP

    BigSkyGP Well-Known Member

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    Couple of reasons.

    What's your distance you were shooting?

    For example a 150gr 308 Win vs 165-168gr 308 Win. 100yd zero, the 150 will drop like 16 inches at 300yds, and the 165-168gr will only drop 8inches.

    There is a happy spot there. Lighter bullets slow down faster, and drop sooner. Heavies carry their slower speed farther before they slow down enough to notice. There's more to it of course.
     

  3. ShortMag3

    ShortMag3 Well-Known Member

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    I am somewhat familiar with the info you provided and it would be more logical if it was at 300 but this was at 100yards???

    Thanks for the input!
     
  4. rscott5028

    rscott5028 Well-Known Member

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    harmonics
    stabilization
    recoil
    shooter
     
  5. WV Sendero

    WV Sendero Well-Known Member

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    +1 on all these plus more reasons. 200fps difference either direction (at ~2500fps)by itself would have very little affect on trajectory at only 100yds. Same thing happens with different loads in the same gun, with the same weight bullet at roughly the same speeds. They both may shoot the same size group at the same speed but at different places on the target. Each combination of powder, primer, seating, bullet characteristics (not just weight or BC) in a gun can act and impact differently and not always what common sense leads us to expect.
     
  6. Grumulkin

    Grumulkin Well-Known Member

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    There are two reasons:

    1. The heavier bullet which means more recoil.

    2. The lower velocity which means the barrel rises a bit more under recoil before the bullet exits the barrel.