Ballistic Coefficient vs. Accuracy?

[Distant Thunder]

As I read more on the transonic zone, I find that there is one group of shooters who are working hard at understand what it takes to travel through this troublesome velocity range and remain on course, that group is the long-range precision shooters. They are experimenting with different ideas in an effort to extend the maximum range of their bullets, which until recently was accepted as being whatever distance to which they remained supersonic and then they hit a wall, the transonic wall. Their super slick VLD bullets could not be counted on to transition to subsonic with accuracy reliably.

I think their efforts and the result could be helpful in understanding how our bullets can better travel through the transonic zone and emerge from it and still hold true to the original path.

The precision guys had been working on the idea of just spinning their bullets as fast as possible or faster and enter the zone at a high rpm, but since bullets degrade in forward velocity more rapidly than they do in rotational velocity they can end up with bullets that don't track on the trajectory path. Overspinning can cause the bullet to remain parallel to the axis of the bore due to the very high static stability, gyroscopic spin, and as the path arcs down toward the target the nose stays above the path of the trajectory, this lowers the dynamic stability which is needed to remain stable through the transonic zone where the destabilizing force are stronger.

Some of those boys are working with bullets that will just statically stabile when they enter the transonic zone and track much better with the nose down and following the trajectory arc. That leaves the bullet with better dynamic stability and they are having success with that approach. They are running bullets that are at the upper end of the length that will be stabile as the bullet slows to the 1346 fps upper end of the transonic zone.

They are even shooting different length, weight, bullets to match the conditions so as to time the drop in forward velocity with the rotation decay and be at a good dynamic stability as they enter the zone.

Looking at the velocity most BPTR shooters operate at and the 900 yard phenomenon this approach is most likely to help us at 900 and 1000 yards. However, when you factor in all of the things that can change the speed of sound and the velocity of our bullets downrange it's not going to be feasible to just load a different bullet/load for each match, each range, each altitude and the different times of the year. My guess would be that picking a bullet and load that hits the middle ground is the best we can do.

Still the information could be used to help fine tune a long-range bullet and load that will perform best in our velocity range.

As I read more on the transonic zone I gain a little better understanding of what bullet design works best and why. I'm slowly putting it all together, the main thing I took form what I've read lately is the difference between static and dynamic stability and for me that was a big hurdle. I find it fascinating that a bullet can be spinning at a high rpm with high static stability and be out of line with it's trajectory and lose dynamic stability. A good balance of the two is needed especially in the transonic zone.