I would like to see the same test done at 500yds with a 16" barrel and 7 , 8 and 9 twist to see the difference . Maybe even 1/2 that 250 to 300 yards.
So would I. The two articles both involved a tremendous amount of shooting, and they still didn't do much more than scratch the surface when you start considering variables like barrel length, temperature and longer distances than 100 yards.
It helps to explain why the military went with such a fast twist--they are concerned with the possibility of all those variables "ganging up" on them in a bad way. If you combine short barrels, low temperatures and extended ranges then you need a faster twist to compensate for the sum of the effects than would otherwise seem reasonable.