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Help with ballistics please.

 
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  #15  
Old 02-16-2011, 02:32 PM
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Join Date: Apr 2009
Posts: 183
Re: Help with ballistics please.

You can't enter in a muzzle speed of 2700 fps and get the same rpm that will stablize the bullet at 3100 fps. It is the launch speed that is giving you the rpm to make the bullet stable past what your coming up with. Basically you have found out that you would have to launch that bullet faster then the speeds you are talking about with your twist rate.
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  #16  
Old 02-16-2011, 04:41 PM
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Join Date: Dec 2007
Location: Las Vegas
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Re: Help with ballistics please.

Sorry edge, I was not speaking directly to your comments. I agree with everything you said. I was saying that their are times when bullets become unstable and it has more to do with the whole set up instead of just the velocity. There is no myth that there is a disruption when passing into or out of the the speed of sound, and this disruption has a tendency to cause bullets to destablize. I just don't believe it happens every time no matter what. I have read to many times that certain calibers or loads are no good for 1000 yard shooting because they will go subsonic at say 900 yards. If you actually shot that caliber load combination, there is a good chance it can hold moa to 1000.
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  #17  
Old 02-16-2011, 05:45 PM
KRP KRP is offline
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Location: Kuna, ID
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Re: Help with ballistics please.

Quote:
Originally Posted by robbobsam View Post
What is your barrel twist rate though ???

Is it 1 in 10, or 9 or 8 ???

I have just ran the same calculations with a 1 in 9 and a 1 in 8 twist barrel and as you say it will stay stable for up to 1000yds.
10 twist chambered in 6BR. The calculation is flawed because the formula is for muzzle velocity. Calculate the RPMs of the bullet at your desired range(I'm of no help for the math/info to do this) and enter it into the formula and see what you come up with. A 10%(for example only) loss in velocity does not equate to a 10% loss in RPM after the bullet leaves the barrel.
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  #18  
Old 02-16-2011, 05:49 PM
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Join Date: Jun 2010
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Re: Help with ballistics please.

Thx for all your help guys, Your help is very much appreciated.
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