Winchester performed patterning experiments comparing their jug choke, WS1 to true cylinder and at 20 yards in a 30 inch circle found with cylinder 76 pct of shot was within the circle and with WS1 at 20 yards 87 pct of shot was within the circle. However, at 40 yards the cylinder produced 35 pct of the shot within the 30 inch circle whereas WS1 or the jug choke oddly enough performed worse at 40 yds with only 33 pct of the shot within the 30 inch circle at that greater yardage. This info is from Schwing, Winchesters Finest, The Model 21.
