Curious, what do you think of multiple BC for bullets?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by BrentM, Dec 22, 2013.

  1. BrentM

    BrentM Well-Known Member

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    Been thinking about why Sierra does this and why others don't. Thoughts?
     
  2. emn83

    emn83 Well-Known Member

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    Depends on the BC used, Sierra uses G1, so, using multiple BCs helps make ballistics fit better. Using G7 BC, generally gets more accurate drop/velocity/drift data without using multiple BCs......has to do with bullet shape, G1 doesn't work as well with modern boat tail and VLD bullets as the G7 does....there's more to it, but I don't have my books in front of me to go into it more.

    Check out Bryan Litz's book for a real good look at BC and other things
     

  3. jfseaman

    jfseaman Well-Known Member

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    +1 for Brian's book
     
  4. BrentM

    BrentM Well-Known Member

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    Guess I posed the question incorrectly. Does using the sierra model work, fore example, might have been a better question.

    I noticed my 204 at extended LR drops off faster than the ballistics program with a set BC allows for. Sierra numbers are actually not far off, but I am not shooting their bullet to compare. If I convert a G1 to G7 via Kentucky windage, which is almost 51% of G1, the numbers still don't work right. It could be the bullet was tumbling on me but I tend to not think so. Compouter said it was still at 1250ish. I didn't have enough ammo loaded up to test each yardage point but I will next outing.
     
  5. emn83

    emn83 Well-Known Member

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    Yes, using banded BCs can work. I personally dont, but I'm shooting a 308 out to 600 yards max, at the moment.
     
  6. BrentM

    BrentM Well-Known Member

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    I might be wrong but I don't see this being much of an issue with larger calibers. The smaller ones, such as the 204, might be more of an issue. The 6.5's seem quite good with G7 as far as I have flung them, which is to 1660 yards.