Bullet batch weight variation

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Topshot, Jul 25, 2009.

  1. Topshot

    Topshot Well-Known Member

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    With a crook batch of projectiles. How much of an effect on point of impact would you expect per 1 grain of variation in bullet weight?

    Example, if a sample of 10 bullets were weighed and the bullets varied in weight from 248.5 grains to 251.5 grains. ie 3 grains variation. How would this effect point of impact at 1000 yards?

    Be interested to know as I have a few boxes that are just like this and cant send them back:cool:.
     
  2. learning

    learning Well-Known Member

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    Anyone? Anyone? Bueller? Bueller?

    I was wondering as well. I had the same bullets, but could send them back.
     

  3. jmason

    jmason Well-Known Member

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    "Good Grouper" would probably have an answer for this one. try shooting him a PM with a link to this thread and ask if he'd be kind enough to post a reply. He is a great resource, and a good fellow but hasn't been posting much lately.
     
  4. J E Custom

    J E Custom Well-Known Member

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    The percentage difference in weight will be close to the percentage difference in velocity.

    It is not much but at long range it could be enough to open up your groups.

    For all out accuracy it is recommended that you weight sort your bullets in batches .

    If your using them at 3 or 400 yards it will not make that much difference.

    If your not convinced you can load 5 rounds with the extreme weight variation (Lowest to
    highest) and load 5 that weigh the same and shoot them at the longest distance you feel comfortable with for comparison.

    J E CUSTOM
     
  5. Topshot

    Topshot Well-Known Member

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    Thanks J E,
    I put this question to Bryan Litz after readeding his great new book. Your thoughts pretty much line up with what Bryan had to say.

    This is what he came up with....................................

    ................. "a difference of 2.6 grains is just over 1% variation in weight. Assuming 2900 fps MV, this difference in BC would only affect your drop at 1000 yards by 1.8" (from a 100 yard zero).
    That amount of weight variation would produce the same vertical dispersion as an 8 fps variation in MV"................................................................

    So it seems that with a constant form factor, all you need to do is work out the muzzle velocity variation. Then run the program to work out the trajectory for each of the velocities at the extreme spread. The difference in trajectories is the maximum drop variation, ,maybe?

    As you said "J,E", I will only know after I have shot them for comparision.