Typical Shot Spread Per Choke. At 20 inches the barrel performs about the same as a 24 incher. the choke matters.
Cyl is an unchoked BBL. the stoger has one full and one IC I think. The chart is a little screwed so read the yards and look for the coresponding spread. as you can see out at 50 yards it is pretty wide so you want a lot of ellets thus number 4 or number 1 buck at that range there is still more than enough energy to rip flesh and break bones. at 25 yards it looks like you emptied a sten gun at the target.
Yards10 15 20 25 30 35 40 45 50
Full 10" 15" 20" 25" 30" 35" 40" 45" 50"
Mod. 15" 20" 25" 30" 35" 40" 45" 50"
I/C 20" 25" 30" 35" 40" 45" 50"
Cyl 25" 30" 35" 40" 45" 50"