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Bullet Stabilization Questions

 
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  #8  
Old 01-19-2004, 03:21 PM
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Re: Bullet Stabilization Questions

Ric

Here's something to read if you haven't already seen it..

This is for external ballistics as I understand it and I see no mention of variation caused by non-homogeneous projectile density (jacket thickness and such) and the forces in place when that type projectile exits the barrel. (A physical center that does not match the density center.)
http://www.nennstiel-ruprecht.de/bul..._forcesmoments

[ 01-19-2004: Message edited by: Dave King ]
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  #9  
Old 01-19-2004, 03:23 PM
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Re: Bullet Stabilization Questions

100yds isn't going to show the effects of your ES. (Things like POI shifts due to the barrel coming in & out of it's sweet spot)
I think this is why short range BR shooters can get away with thrown charges. It isn't a measurable effect @100.

I'm in the described above situation. Where I consistently shoot better MOA at longer ranges than short. Can't figure it out.
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  #10  
Old 01-19-2004, 06:36 PM
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Re: Bullet Stabilization Questions

The really funny thing about the tests I had done stated in the post above all had a very small amount of ES. I get alot of ES out of my best load that I now use and it still shoots .25 MOA to 800 yards. Go figure.

Also those tests were done on multiple days, somtimes weeks apart. Mostly at -10 F when there is absolutly no air movment where I shoot.

No, I cant figure that out either.
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  #11  
Old 01-19-2004, 06:49 PM
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Re: Bullet Stabilization Questions

Its probably got something to do with the frozen bullets that you're shooting. [img]images/icons/grin.gif[/img] [img]images/icons/grin.gif[/img] [img]images/icons/grin.gif[/img] [img]images/icons/grin.gif[/img] [img]images/icons/grin.gif[/img]

VH
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  #12  
Old 01-19-2004, 08:17 PM
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Re: Bullet Stabilization Questions

WyoW,1 dominant reason to explain the "shoots great at 100 and not at 600 to 1000" is that the bullets are not the same BC as they are pulled from the box....A lot of shooters that strive for better accuracy would spend lots of time trying to get ES's into the single digit figures and then select an unquailified bullet from the box and shoot away...I can assure you that it's easy to get a .2 difference in the BC of a Match style projectile ...If you take a bullet say of a real world BC of .600 and then another that looks the same with a BC of .580 and to this a distinct possibility of a 25 fps spread ,if you shoot it enough,check out how bad this looks on a Ballistic program if you stack the high to the high and the low to the low..This is part of the reason that a lot of guys struggle in trying to get the Vertical dispersion to say a sub 1/2 min level at 1000yds...If your happy with the top bullet 10 inchs higher that the bottom one in your groups then disregard this post...JR..Jeff Rogers..ps This is practial information as i do not even have a Ballistics program to tell you the theory style differences,you would have to run this data yourself..
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  #13  
Old 01-19-2004, 08:17 PM
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Re: Bullet Stabilization Questions

Suprised no one has mentioned bullet path vortices from prior shots. [img]images/icons/grin.gif[/img]
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  #14  
Old 01-20-2004, 12:38 AM
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Re: Bullet Stabilization Questions

My take on the matter is that it might have a little to do with BC and velocity. Like most here, I dont know or understand why this might happen. Listed below are 2 examples of bullets that should have been MORE than stable, yet what these 2 examples have in common is their low BC.

Example 1:
I had a load for my 308 win that I dont have anymore. It was a 150 nosler BT at 3100 FPS at the muzzle. It would group ragged 1 holes at 100, and 1.5" at 400 yards. At 600 yards it was 1 MOA or 6 inches at 1k they were sideways. Twist was 12. BC is .435 and it would get worse with velocity decay.

Example 2:
My new 308. Had a 168 grain load at 2600. It would group .25" at 100 and .750 at 300, 1.5 at 400 and 6" at 600 at 1000 they were also sideways. The BC from that bullet in my rifle was .450 Twist was 11.25

Both loads were tested in cold dense air. Both had a poor BC and the one with the highest BC had a lower MV.

Now for the kicker. The 168 grain load was increased to 2661 FPS in the same conditions. It shot .3-.5 MOA at 100 yards. It shot .3-.5 MOA at 600 yards. It shot almost perfectly straight holes at 1k (slightly oblonged) and exactly 1 MOA or 10".

Could it maybe that the velcoity to BC ratio had somthing to do with it?

I also have lower velocity loads with very high BC's and are in the 1.5 GSF zone instead of 2.0 or 2.5 and because they have the high BC they retain their super sonic velocity farther even in the same cold air, they also maintain their accuracy to 1k. I think that bullets "know" for lack of a better term where they are in the speed of sound barrier and accuracy may be invloved. May be there is some relationship between each of these.

Many unknown mysteries here and alot of speculation. This is just what I have found in my tests.

Also these are thoughts and opinions and speculation and guesses, I dont KNOW why this occurs.

Any particular loads this is happening with??

[ 01-19-2004: Message edited by: meichele ]
__________________
Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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