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Thread: I could use some help with BC values on 38-55 and 32-20

  1. #1
    Boolit Mold D-gunner's Avatar
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    I could use some help with BC values on 38-55 and 32-20

    I am currently shooting Jamison 32-20 Win 115 Grain RNFP....... AND,,,,,,,, 38-55 Win 255 Grain RNFP. They are not able to tell me the Ballistic coefficients of these rounds. Can anyone out there help me with these numbers?

  2. #2
    Boolit Grand Master


    Larry Gibson's Avatar
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    A profile picture of the bullets would help?

    Larry Gibson

  3. #3
    Boolit Master Norbrat's Avatar
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    Put your bullet profiles in here http://tmtpages.com/calcbc/calcbc.htm

  4. #4
    Boolit Mold D-gunner's Avatar
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    Click image for larger version. 

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  5. #5
    Boolit Grand Master


    Larry Gibson's Avatar
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    I'd use a BC of .15 on the 32-20 bullet and a BC of .27 on the 38-55 bullet.

    Larry Gibson

  6. #6
    Boolit Grand Master


    Larry Gibson's Avatar
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    Quote Originally Posted by Norbrat View Post
    Put your bullet profiles in here http://tmtpages.com/calcbc/calcbc.htm
    That calculator works fairly well with jacketed bullets. However, most all BC calculators as such always give a higher BC with cast bullets than they actually pan out at. I measure BCs; the M43 Oehler PBL measures time of flight between muzzle screens and screens in front of the target at 100 yards. The "calculators" do not take into account the turbulence/drag created by the lube grooves. I've not found any measured BC of a cast bullet be the same as calculated. The measured BCs are always a bit lower.

    Larry Gibson

  7. #7
    Boolit Grand Master

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    BCs arnt a solid thing either as they do change for the same bullet slightly with velocities ranges. I would think Larry G's are pretty close on my guess. I have the Lab Radar chronograph and it gives 5 readings down range to work with figuring BCs. It is interesting to see the velocity drop over 200 yds in increments to the target.

  8. #8
    Boolit Mold D-gunner's Avatar
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    Thanks Larry! This will really help me out. Maybe with some study I can learn the charts.

    Quote Originally Posted by Larry Gibson View Post
    I'd use a BC of .15 on the 32-20 bullet and a BC of .27 on the 38-55 bullet.

    Larry Gibson

  9. #9
    Boolit Master
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    Lyman's books have BC's & depictions of various cast & jacketed bullets.

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