Bullet stabilization and about it all

[treeman]

I found this worth sharing, I think it explains a lot and brings a lot of bits together.
https://anarchangel.blogspot.com/2007/01/stabilization-mythology.html

You welcome to fault it, would like to hear opinions ??

[ravingDIODE]

Very interesting! If that is all true then i sure learned a few new things and also believed one or two things wrong. I new bullet length played a role but thought it was because of the surface area touching the barrel.

[janfred]

Mostly accurate, but.....

I do not shoot 5.56 or .223, and perhaps some witchcraft is involved in the AR platform. In other calibres, experts have concluded that if the bullet comes out of the barrel dynamically stable, it will stay stable all the way until the transonic stage. Bullets linear velocity reduces much faster than the spin; i.e. bullets become more dynamically stable downrange. Key stability points are muzzle exit, transonic zone and/or target.

Bryan Litz explains it much better in his books than me.

[treeman]

[QUOTE=janfred;1313037]Mostly accurate, but.....

I do not shoot 5.56 or .223, ............. if the bullet comes out of the barrel dynamically stable, it will stay stable all the way until the transonic stage. Bullets linear velocity reduces much faster than the spin; i.e. bullets become more dynamically stable downrange. Key stability points are muzzle exit, transonic zone and/or target.
......................
I got the idea thats what he said as well ?

[ravingDIODE]

I got the idea thats what he said as well ?

Felt that was also pretty much the jist of it?

[Toxxyc]

Didnt' read the whole thing, but does he touch on spin drift?

[janfred]

[QUOTE=treeman;1313038]

Mostly accurate, but.....

I do not shoot 5.56 or .223, ............. if the bullet comes out of the barrel dynamically stable, it will stay stable all the way until the transonic stage. Bullets linear velocity reduces much faster than the spin; i.e. bullets become more dynamically stable downrange. Key stability points are muzzle exit, transonic zone and/or target.
......................
I got the idea thats what he said as well ?

Well, not quite.

I quote,

"There seem to be a few critical destabilization points, or points where the natural tendency to be disturbed are greatest. These tend to be when the bullet first leaves the muzzle, and/or clears the muzzle blast, when linear velocity slows by 1/3, when the bullet drops below 2500fps, when the bullet drops below 1500fps, when the rotational velocity slows by about 1/3, and when the bullet drops under supersonic."

And

"The same 75gr bullet fired from a 1:9 barrel will most likely not go unstable 'til well past 100 yards, and even may be stable out past 300 yards (depending on bullet design)."

[Pirate]

I really don't get how he arrives at his quoted downrange destabilisation argument. The bullet is most unstable the moment it leaves the barrel. As the speed (and therefore the upsetting moment) tying to overcome the gyroscopic stabilization is then greatest.

The accepted current authority on this is JBM Ballistics. The Greenhill formula has a number of problems with it, while the Miller formula adress those.

https://www.jbmballistics.com/ballis...iography.shtml

The first reference under "External" on the link above is what you want to look at.

There's an online calculator of this on the JBM Ballistics website.

[Messor]

I really don't get how

I really don't get how in the year 2019 we still need to debate this topic at all.

[Pirate]

I really don't get how in the year 2019 we still need to debate this topic at all.

Unfortunately old info on the internet is forever... and seems to surface with annoying regularity