When does bullet stability diminish?
- Thread starter VANCE
- Start date
Probably the definitive study of bullet stability in flight is by Brian Litz in his book "Applied Ballistics for Long Range Shooting".
His analysis begins at about p. 159.
There was a post/discussion on stability on the old Forum, and I believe it was transferred to this new Forum.
You might try searching for "Stability"?
In a nutshell:
The RPMs of a bullet decays more slowly than velocity as the bullet travels forward in distance. A bullet's gyroscopic stability actually increases for a while as the bullet travels forward.
Dynamic instability increases as the bullet slows down and becomes transonic in speed. This occurs at about 1300 fps and for most modern centerfire cartridges, at about 1,000 yds distance.
Basically, stability is a product of both barrel twist and velocity.
His analysis begins at about p. 159.
There was a post/discussion on stability on the old Forum, and I believe it was transferred to this new Forum.
You might try searching for "Stability"?
In a nutshell:
The RPMs of a bullet decays more slowly than velocity as the bullet travels forward in distance. A bullet's gyroscopic stability actually increases for a while as the bullet travels forward.
Dynamic instability increases as the bullet slows down and becomes transonic in speed. This occurs at about 1300 fps and for most modern centerfire cartridges, at about 1,000 yds distance.
Basically, stability is a product of both barrel twist and velocity.
Not being troublesome, but it can be unstable from the muzzle.
If you plug into an online calculator like JBM (free) and plug in your starting parameters. You will be off to a good start.
Goal in flight should be 1.5 SG, under that you will lose BC. For terminal some of us prefer 2.0 SG.
If you shoot into the transonic range a little more may help.
If you plug into an online calculator like JBM (free) and plug in your starting parameters. You will be off to a good start.
Goal in flight should be 1.5 SG, under that you will lose BC. For terminal some of us prefer 2.0 SG.
If you shoot into the transonic range a little more may help.
Entropy! The second it leaves the barrel.
This question is twofold IMO, flight stability and terminal stability. Standard flight stability is great for punching paper but does not offer the best parameter for terminal performance for Hammers. @Farleg has proven this extensively.
If the shooter adheres to the bullet operational specs of twist and minimal velocity for terminal performance at 1750fps, it will be stable in all likelihood.
This is where most of us strive to be having BOTH factors by having the right twist for the bullet to achieve a SG of closer to 2.0 to maintain best flight stability with best terminal performance. Best twist to yield highest RPM's with velocity is going to keep bullet at its peak performance (flight and terminal performance stability).
However, as @ButterBean has encountered, too fast of twist can be detrimental when hyper-velocity detracts from bullet performance. Then again, there is laser fast and there is @ButterBean "light speed" fast!
