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Barrel Twist

 
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  #1  
Old 08-01-2005, 03:10 PM
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Join Date: May 2005
Location: UK
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Barrel Twist

Gents

I post asking for advice [img]/ubbthreads/images/graemlins/smile.gif[/img] as you all know alot more about such matters than I.

I am in the process of ordering my first LR rifle (Cal .308)and have been advised to have a barrel with a 1 in 11 or 12 twist for either a 168g or 180 grain bullet.

My research indicates that this barrel is only good for stabilizing the bullet if it is travelling at less than 2800fps. Is my research correct?

If I push the bullet above the 2800fps threshold would I limit barrel life or create throat errosion etc and would it adversely affect accuracy?

My concerns are round the fact that I think I am being pushed into getting something that may not be truly acceptable and appropriate merely something this rifle manufacture supplies.

As you will appreciate, this will be the most expensive rifle I will probably buy and currently its my dream [img]/ubbthreads/images/graemlins/smile.gif[/img] I don't want it to become an expensive nightmare, any help or advice would be greatly appreciated.

Thanks

H
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  #2  
Old 08-01-2005, 03:28 PM
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Re: Barrel Twist

a 1 in 12 will stabilise up to 190gr bullets normally, without any worries. i don't know where you are getting your info from, but my understanding of it is that the faster you push the bullet, the more stabilised it becomes, although velocity will not compensate for too slow a twist rate in the first instance.

anyway, 1 in 11 or 1 in 12 no problems.
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  #3  
Old 08-01-2005, 04:07 PM
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Join Date: May 2005
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Re: Barrel Twist

Nowler

According to the Greenhill formulae I have the following data:

Bullet length 1.139" to 1.237" = 1 in 12 twist for a velocity less than 2800fps.

or

Bullet length 1.178" to 1.264" = 1 in 14 twist for a velocity more than 2800fps.

This is all for a 180g Sierra Gameking round at 1.2055" in length. I accept the bullet is a hunting round but I will be using it for both LR and hunting. So you see the dilema, I'm being told a 1 in 11 or 1 in 12 and the data says a 1 in 14 if I go above 2800fps.
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  #4  
Old 08-01-2005, 04:38 PM
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Re: Barrel Twist

Remember that the Greenhill formulia gives you the MINIMUM twist required to stablize the length of bullet being used. Within reason, going with a faster twist is better (1-12 is faster than 1-14)
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  #5  
Old 08-01-2005, 04:53 PM
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Join Date: Jan 2003
Location: The rifle range, or archery range or behind the computer in Alaska
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Re: Barrel Twist

Best twists for 308 with various bullets:

190 1-12 min (1-11 or 11.25 Best)2400-2650

175, 178, 180 12 works VERY well (2400-2750)

168 1-12, 1-13, and even 1-14 works well (2500-2900)

150-155's 1-14 through 1-12 works well depending on weather or not youre using Senars or others. (2600-3000)

Weather or not you use formulas or real world conditions, you will find that the numbers above will work very well in most conditions.
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Quote:
Originally Posted by Broz View Post
Please just answer one very simple question. Why would anyone shooting long range load a low BC , low SD 168 gr offering in a 300 win???????

My answer to this is. The only reason is to make the 7 RM look good. There is no other reason.

Jeff.
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  #6  
Old 08-01-2005, 07:46 PM
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Re: Barrel Twist

[ QUOTE ]
My research indicates that this barrel is only good for stabilizing the bullet if it is travelling at less than 2800fps. Is my research correct?

[/ QUOTE ]

Your research is weak so far.
Do you think a bullet would be less stable ABOVE 2800?
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  #7  
Old 08-03-2005, 04:34 AM
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Join Date: May 2005
Location: UK
Posts: 53
Re: Barrel Twist

TG & M

Many thanks for that I appreciate the time you took to respond it has helped me a lot.

Mikecr

With respect I suggest you read my post again, as three members have understood my question I make the diagnosis my ability to get across my point is logical and understood. I have clearly made my point that my knowledge is limited so to be told it is weak adds nothing to me trying to learn, but hey! thanks for posting.
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