My personal experience with it is this. For heavy loads in large shot size it helps. The smaller the shot the more fluid like properties the shot will have. The larger the shot size the more room for realignment is needed. A forcing cone gives you that room to allow the shot column to rearrange.
I've read the same, however the pellets are randomly encased in the shotcup. Ignition jostles them around some more, and then they get jammed into a longer forcing cone and they somehow are consistently rearranged into a more pattern consistent shape. Not sure I can buy into the theory. I can see how any overbore reduces the amount of pellet deformation, which will certainly improve patterns, but a 2.5inch FC consistently causing an improvement in pellet arrangement that will be seen downrange? Perhaps it is so, but as of yet I'm not buying into it.
In addition, this improved rearrangement consistently happens in milliseconds?
