Temp/Humidity effects on projectile flight

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by peterb, Feb 15, 2010.

  1. peterb

    peterb Active Member

    Messages:
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    Joined:
    Jul 17, 2008
    Hi all, two questions that I have been chewing on for a while and have decided to throw it up for the experts.(Or those with a greater expertise than mine!)
    1: In the Spring of 2009 with those warm sunny days (20 - 25 c) and green grass, I zeroed a new Nightforce scope on my 308. Recently, I began to get the feeling it was shooting low, and when I checked it, found point of impact 1/2"low at 100yds. Bullet is Remington 165 grain Boat tail Accutip factory.
    The weather we have been experiencing in the South West of West Oz has been 30 c plus, accompanied with around 30 % humidity.
    Would this have such a great effect on the point of impact ?
    2: Angle Cosine Indicator - does using one of these require more mathmatics than the Angle Degree Indicator? Ie more difficult to use. I am not carrying ballistic software, but just a card that has what I deem relevant info.

    And, be patient, you can teach an old dog new tricks ! :D

    Cheers,
    Peter