[reynolds357]

Originally Posted by Unclenick

Reynolds357,

1.5 is a commonly cited optimal stability number, not a minimum stability number. If Berger said otherwise, they are wrong, but I would be surprised to learn Bryan Litz let them publish that basic a mistake. 1.0 is the minimum for stability because that is how the gyroscopic stability factor is defined. Under 1.0 is unstable, over 1.0 is stable. It is true for all projectiles. It's just that being barely over 1.0, while stable, does not produce best accuracy and allows enough sustained coning motion in a spin-stabilized projectile to degrade BC some by adding to drag. The best value depends upon what authority you listen to. Spinning faster increases stability, but it also increases wobble due to any imperfections in the mass symmetry of the projectile all the way up until the thing spins so fast it flies apart. Where the best compromise between minimum spin and excessive spin occurs depends on the authority you are listening to. Harold Vaughn liked 1.4, Don Miller liked 1.5; Sierra told me long ago that 1.3 to 3.0 was good for hunting accuracy and 1.4 to 1.7 was for match accuracy.

Actually, they call 1.0 to less than 1.5 "marginal".