Originally Posted by
Larry Gibson
Thanks Tim, I get what Eutectic was saying now;
"Since the RPM remains the same the stability of the bullet remains the same, the distance travelled per revolution is not the driving factor in bullet stability just the RPM achieved."
The rate of twist part of the equation is established by the twist with the bullet in the barrel in the barrel, not any distance the bullet travels outside the barrel. The measurement of the velocity (while I measure the velocity outside the barrel the M43 Computer, knowing the BC, distance to the start screen and other variables converts the measured velocity back to muzzle velocity. The velocity simply establishes the time element in the equation.
What Eutectic is talking about is the reason why the group dispersion is non linear once the bullet has gone beyond that RPM Threshold. It is most noticeable with the helical arc that increases in a larger diameter as the range increases. It is because the RPM remains constant while the distance traveled is less per the RPM. Essentially as the range increases more RPMs are traveled for the distance traveled which means the helical arc increases in a non linear fashion. Hard to get one's head wrapped around that but once there it makes perfect sense.
Larry Gibson