Originally Posted by MontanaRifleman
In reading the 10th chapter as you suggested, Litz described dynamic stability as a type of stability that gets a bullet through the transonic zone. This isn't the case with the above example. Not sure what's going on there as I realize in theory that a bullet should become more stable the farther down range it goes. The guys at Cutting Edge did tell him to possibly expect that.
I'll be running them in my 300 RUM at higher elevations and velocity. It will interesting to see how they do.
From Litz 2009 p. 160 (Emphasis in the original):
It's common knowledge that bullets fired with adequate gyroscopic stability can become unstable at long range, tumble, and keyhole in the target. Most shooters assume that the problem is a lack of gyroscopic stability, and sometimes try to remedy it by using a faster twist barrel. A faster twist barrel certainly does increase the gyroscopic stability of the bullet both at the muzzle and downrange. However, when a bullet tumbles at long range, it's not because of a lack of gyroscopic stability, but through a lack of dynamic stability.
At Litz goes on to explain, this effect most commonly is seen somewhere around the sonic transition, but there are cases where lack of dynamic stability causes tumbling at long range even though the bullet is nowhere near the sonic transition. The dynamic stability condition is complex (see: http://www.nennstiel-ruprecht.de/bullfly/dynacond.htm
). Even though it may not immediately be clear in this case why the bullet becomes dynamically unstable, it is clear that the dynamic stability rather than the gyroscopic stability is the problem. A faster twist barrel may not fix the problem. All of the terms in the dynamic stability equation are characteristics of the bullet itself. Increasing the gyroscopic stability (with faster twist) is hopeless if the dynamic stability becomes equal to one and the dynamic stability condition becomes impossible to fulfill.
If the bullet has dynamic stability problems, faster twist rates, higher elevations, and higher muzzle velocity can (at best) push the onset of dynamic instability out to longer ranges. But if the problem is already appearing at 600 yards, I would be surprised if the bullet can ever be made to shoot reliably at 1500 yards.