If Dan were to measure the ROT of his good shootin' barrel there, and he did it conventionally, the result would be average ROT. Short sections of barrel have to be measured to see the rate of gain.
But then from my perspective the rate of gain is irrelevant so long as positive and the ROT is crucial to stabilize the projectile type used. Also that you can "overspin" a ball without terrible consequences so long as the ball is well-cast and free of voids, but under-spinning a long bullet will give you a wobbly projectile.
Fine shooting Dan, your gun and skills is/are legend. It has been mentioned some here when you weren't much posting.