Haven't held a Holland 20 between my hands and can't measure minor variances in the twist with certainty but the 8's 10's and 12's don't seem to vary. One other point, Holland and Westley were just as concerned with patterning their rifled choke guns as their accuracy, I would think more so with a 20. Westley Faunetas have a three groove choke. With the rifled choke guns all the "magic" is in the that last several inches of the barrels.