MV is of course of little value in calculating leads, what counts is time of flight. Using an old chart from WW for lead #5's at 40yds a 1330fps mv load has a TOF of .1210 seconds, while one of 1135 fps mv has a TOF of .1365 secs. A bird traveling 50 mph = 73.333 fps would require a lead of 8.87 ft for the fast load & one of 10 ft for the slow one. Note this is a difference of 13.56 inches & is a "Fast" bird & must be traveling at 90° to shot line & this is extremes in shot velocities.
With 7½s the leds become 9.47ft & 10.6ft with the difference still 13.56 inches. This old chart did not include data for 1400 fps loads.
