Steve Fisher, aka Yeti, of Sentinel Concepts and Jeff Bloovman of Armed Dynamics, compare different loads in three different shotguns. They use a Robar Remington 1100, Benelli M1 Super 90, and a NEF H&R Pardner Pump. They show how the same loads can have different patterns out of different shotguns.
They show some very interesting results. I would not have expected such a difference from the same ammo shooting out of three different guns.