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ballistic coefficient questions . 6.5 mm bullets

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  #29  
Unread 01-14-2013, 09:57 AM
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Re: ballistic coefficient questions . 6.5 mm bullets

That is some crazy fast twist... I guess I can see that if you are at sea level but wow! 7" twist in a 6.5 magnum.... you sure could make a purty shotgun pattern out of the Bergers with that couldn't you?

The 130's stabilize just fine out of my 8.4" twist.... which is substantially slower than recommended...


I'm not put off yet I'll let everyone know what I find out.


t
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  •   #30  
    Unread 01-14-2013, 01:57 PM
    Edd Edd is online now
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    Re: ballistic coefficient questions . 6.5 mm bullets

    The Berger twist rate calculator shows that CE 130 gr bullet with an 8.4 twist starts dropping below the desired minimum 1.5 stability factor at an altitude of 3000 ft.

    An 8 twist maintains 1.5 or above down to 300 ft and a 7.5 twist is 1.68 at sea level.
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      #31  
    Unread 01-14-2013, 02:11 PM
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    Re: ballistic coefficient questions . 6.5 mm bullets

    Quote:
    Quote:
    Originally Posted by Edd View Post
    The Berger twist rate calculator shows that CE 130 gr bullet with an 8.4 twist starts dropping below the desired minimum 1.5 stability factor at an altitude of 3000 ft.

    An 8 twist maintains 1.5 or above down to 300 ft and a 7.5 twist is 1.68 at sea level.
    What velocity range is that SF for?

    I talked with CE this morning and they do have a 141 gr 6.5 bullet. I need to contact Dan for more info on OAL, BC and twist
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      #32  
    Unread 01-14-2013, 03:01 PM
    Edd Edd is online now
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    Re: ballistic coefficient questions . 6.5 mm bullets

    Quote:
    Originally Posted by MontanaRifleman View Post
    What velocity range is that SF for?
    3000fps and 59 F temps
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      #33  
    Unread 01-14-2013, 03:11 PM
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    Re: ballistic coefficient questions . 6.5 mm bullets

    Quote:
    Originally Posted by Edd View Post
    3000fps and 59 F temps


    That would make the difference I suppose. I'm at 4300ft ASL & a "wee" bit faster in velocity dept.


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      #34  
    Unread 01-14-2013, 03:11 PM
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    Re: ballistic coefficient questions . 6.5 mm bullets

    Outlaw is shooting them @ 3400 fps
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      #35  
    Unread 01-14-2013, 03:12 PM
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    Re: ballistic coefficient questions . 6.5 mm bullets

    Quote:
    Originally Posted by MontanaRifleman View Post
    What velocity range is that SF for?

    I talked with CE this morning and they do have a 141 gr 6.5 bullet. I need to contact Dan for more info on OAL, BC and twist

    I emailed their tech line but haven't gotten a response yet. Was the 141 a hunting type bullet or?

    t
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