I thought that a longer slug provides a better lever for the correcting moment, to force the projectile to follow its projectile with less yaw? Assuming the center of form and center of mass are also further apart.

With gyroscopic stability, there is also the problem that the transverse inertia gets bigger at a faster rate than the rotational inertia, further reducing gyroscopic stability. As a result, faster twist rates are needed.

This thread is about slugs, not pellets, however there is another by Miles in a Sticky below you may find interesting....Bob

Yes, Miles. If you were stuck with one barrel, then long projectiles could easily drop below your imposed stability factor of 1.5. But, for this exercise you already sated that all projectiles would be fired from whatever twist barrels would be required to yield 1.5 stability factor, at a muzzle velocity of 950 FPS. The reason for my question was that your chart for predicted group size seemed to favor much shorter projectiles that I expected, even when barrels that has fast enough twist to provide a stability factor of 1.5 would be available.

Miles would be the guy to ask about that.... I would like to know as well what is needed to produce consistent fractional MOA groups..... I presume extremely well made bullets is the key, but are there other factors as well?....Bob