Right, Dave. I was digging around yesterday, and noted that one bbl that was cut from 28 to 20" dropped velocity about 42 FPS, IIRC. There's that much variation between shells in a box of field loads.
Choke is the biggest factor in spread,then there's things like shot hardness, velocity,bore diameter, the phases of the moon, etc. Shotgun ballistics are arcane as heck.
Longer bbls tend to be more weight forward, or "Muzzle Heavy". This adds a bit of inertia, helping the swing.
HTH...