How far can a rifle shoot effectively? How does the .408 Chey Tac attain balanced flight? What twist rate is best for extreme long range applications? To answer these questions, there is an outer barrier to be aware of. Your maximum effective range may be limited to your max super-sonic range depending on how well your bullet passes through the transonic zone.
In this video, Rex discussed the behavior of a rifle bullet passing though he transonic zone. The transonic The Transonic zone lies between about Mach 1.2 and 0.8.
The Centre of Pressure (CP) of most bullets shifts around as the angle of attack changes and as velocities decays. The CP experiences a dramatic shift when it crosses the sonic barrier. This shift negatively affects the (dynamic) stability of the bullet. This loss in dynamic stability can cause significant shot dispersion in which coning motion starts, & if it is not damped out it may encounter uncontrollable tumbling. Mathematically correcting for the erratic ballistic behavior of bullets that have passed through the transonic region is extremely difficult. Air density also has a significant effect on dynamic stability during the transonic transition. Thus, thin air poses less of a problem.
Tractability
Tractability factor characterizes the ability of the projectile's longitudinal axis to follow the bending trajectory. The tractability factor is proportional to the inverse of the gyroscopic (static) stability factor. The greater the static stability, the lower the tractability factor -- which can often translate decreased dynamic stability at extreme long ranges.
Balanced Flight
Balanced flight technology utilizes a combination of both projectile profile and special rifling design that ensures the bullet's rotational rate decays proportionally to the decay of its forward velocity. This loosens up the bullets axis of rotation downrange so that its nose can stay on track with the line of trajectory throughout the
