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Is my twist rate OK for my 7mm??

 
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  #15  
Old 01-28-2013, 09:25 AM
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Location: SW Montana
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Re: Is my twist rate OK for my 7mm??

Bullets don't stabilize for a short time then fall apart, once stable they usually stay stable for quite some time which is much farther than most will shoot.
It's good to check your twist rate, I've received the wrong barrel but didn't know it till I checked which turned out OK since my elevation allows me to stabilize bullets with a slower twist rate.
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  #16  
Old 01-28-2013, 10:34 AM
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Re: Is my twist rate OK for my 7mm??

So would you say that if is shooting perfect at 100 it will still be stable at 800??
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  #17  
Old 01-28-2013, 11:40 AM
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Re: Is my twist rate OK for my 7mm??

Quote:
Quote:
Originally Posted by Ingwe View Post
Montana,

Yes I do have a custom Hart barrel. My recipt says 1:10 but I should measure it.

The Accubond actually is longer than the VLD. I am talking about the Berger VLD Custom Hunter which was made to saami specs to fit in standard chambers, so it is shorter than the AB.

The AB is perfect at 100 yards, but I am wondering if it is stable at 500...
I just happen to have a box of those 160 AB's and they are very slightly shorter than advertized, 1.405 vs 1.410, but still longer than the Berger 168 Classic Hunter. Their advertised BC of .531 could be close based on the Bergers advertised BC. I guess it's their poly tip that gives them more length.


Quote:
Originally Posted by Ingwe View Post
So would you say that if is shooting perfect at 100 it will still be stable at 800??
I would say so, but you are on the edge of stability which could lead to terminal instability.. maybe not? You might want to give the Berger Classic Hunters a try, as they will stabilize better and have a better BC.
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  #18  
Old 01-28-2013, 12:49 PM
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Re: Is my twist rate OK for my 7mm??

Quote:
Originally Posted by Ingwe View Post
So would you say that if is shooting perfect at 100 it will still be stable at 800??

Yes that is correct, if a bullet is stabilized when it leaves your barrel it will remain stable until it reaches the sound barrier. A bullet flying down range does loose rpm, but at a slower rate than it looses velocity, so it will actually become more stable the farther down range it goes. The reason for that is because the slower a bullet goes the less force there is applied to the meplat trying to flip it over (cause it to tumble). Bullet simply cannot become unstabile in flight, unless it encounters major forces sufficient enough to over come it's gyroscopic forces. An example of those forces are, the shock waves encountered at the transonic stage, or a physical object.

A good explanation can be found here starting at the very end of the 4th page
http://www.appliedballisticsllc.com/...ding_part2.pdf
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Last edited by Joe King; 01-28-2013 at 01:29 PM.
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  #19  
Old 01-28-2013, 05:39 PM
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Re: Is my twist rate OK for my 7mm??

Great responses fellas and thank you for you taking the time with answering my questions.

I think that I am going to give the new 150gr Accubond LR a try.
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