Estimating BC ....help!

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Brown Dog, Feb 24, 2006.

  1. Brown Dog

    Brown Dog Writers Guild

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    Got 50rds of 308 Geco 170gr target ammo for which I’m having trouble finding / estimating a ‘starting point’ BC to put me 'in the Parish' before I launch any downrange tomorrow.

    They have good ogives but flat tips….....I’m confused!!
    (yes, despite appearances,they are marketed as target bullets).

    What would you estimate (I believe they are flat base)??:

    Geco in the middle, 165gameking on left (0.404), 165NBT on right (0.475)……the ogives appear similar….just the tips seem different:
    [​IMG]


    The ogive is looks too good to class them with the Sierra Prohunter 170 FN (BC: 0.204).

    Some more views of the Geco 170gr tip:


    [​IMG] [​IMG]



    Anyone got anything more edumacated than (0404 + 0.475 + 0.204)/3 = 0.361 ?


    Thanks!
     
  2. POP

    POP Well-Known Member

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    .350?
     

  3. POP

    POP Well-Known Member

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  4. Buffalobob

    Buffalobob Writers Guild

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    look at the Speer 30 cal Mag Tips

    170 gr has a BC of 0.304
    180 gr has a BC 0f 0.352
     
  5. Brown Dog

    Brown Dog Writers Guild

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    Thanks.

    That's brought the average down to about 0.34.

    -I'll give it a go at that!
     
  6. wapiti13

    wapiti13 Well-Known Member

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    BD, Unfortunately, flat nosed, flat based bullets have a much lower BC. Hopefully, they shoot great to offset their range limitations. Good luck.