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how fast is to fast-Berger VLDs

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  #8  
Unread 04-03-2012, 06:08 PM
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Re: how fast is to fast-Berger VLDs

Quote:
Originally Posted by meatyrem View Post
The Berger site lists the 180gr to have a 9 twist.
And the 168gr to have a 10 twist
Not to nit-pick... but, thought it might be worth clarifying...

Unless we're talking about rifled shotgun slugs, bullets don't usually "have" a twist.

So, I think you meant to say that Berger recommends that you use them in a rifle with a twist that is at least as fast as those listed in order to effectively stabilize these bullets under most atmospheric conditions.

-- richard
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  •   #9  
    Unread 04-03-2012, 06:43 PM
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    Re: how fast is to fast-Berger VLDs

    Quote:
    Originally Posted by rscott5028 View Post
    Not to nit-pick... but, thought it might be worth clarifying...

    Unless we're talking about rifled shotgun slugs, bullets don't usually "have" a twist.

    So, I think you meant to say that Berger recommends that you use them in a rifle with a twist that is at least as fast as those listed in order to effectively stabilize these bullets under most atmospheric conditions.

    -- richard
    Yes that is what was meant by that was the twist of the barrel. I'm not too sure if Berger makes slugs tho. Lol
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      #10  
    Unread 04-04-2012, 06:53 AM
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    Re: how fast is to fast-Berger VLDs

    Quote:
    Originally Posted by meatyrem View Post
    You never did mention what twist your barrel has?
    I have a factory sendero II. I think it's 1 in 9.5.

    Last edited by oldmossy; 04-04-2012 at 07:53 AM.
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      #11  
    Unread 04-04-2012, 07:21 AM
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    Re: how fast is to fast-Berger VLDs

    Just wondering why I would be getting the speeds I am getting with my factory 7mm rum. Shooting at 2500 ft elevation. Shooting 93 grains of retumbo. Shooting 180 bergers.Getting 3300 fps. I see this is faster than all the oth er rums. Is my chrono not accurate?
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      #12  
    Unread 04-04-2012, 06:29 PM
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    Re: how fast is to fast-Berger VLDs

    Quote:
    Originally Posted by bigngreen View Post
    Why does slowing the twist or just adding a few thou to the jacket ,with no exterior design change, help if this is what was happening?
    I dont have all the answers to exterior ballistics but one of the reasons for a slower twist and increased accuracy could be
    1- magnus effect. the faster a bullet leaves the barrel the higher the rpm it is spinning at. at 3200 fps and 1/9.5 a bullet is spinning at 242496 rpm, at 3200 fps and 1/11 is spinning at 209280. think of a top spinning it fights gravity and wants to "stand up" The more the bullet stands the harder it is to predict the shockwave/pressure areas and the more they will change with atmospherics. the slower the spin the more the bullet will want to lie parallel to the direction it is traveling. This helps with wind effects also.
    a bullet coming apart would probably start in the chamber under high pressures and may not directly correlate to velocities but may also relate to twist rate as faster rates cause higher pressures. a thicker jacket may help with this.
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