I have a little Mossberg 500 tactical turkey gun with a 20 inch barrel that will put 90 pellets from a 3 inchWinchester Supreme number 5 in a 8 inch circle at 40 yards with a Primos Jellyhead choke tube.
The length ofthe barrel is no longer the major factor in how a shotgun patterns. Findingthe right choke/ammo combination for a particular shotgun is far more important.