Premium buckshot has a shot cup, buffering added to keep the buckshot from deforming against one another. Please explain what feature is present, not present, that indicates the manufacturer "designed" it for cylinder bore. How would a shell be "designed" to be used in a modified choke? Explain please.
Fed Flite Control wad is designed to stick with the shot column for a while outside the bbl, so the usual dispersion effect is delayed for a time and a few yards down range. Usually makes for tighter buck patterns. Choke it down and it will strip/fall off earlier.
Fed Flitecontrol is good stuff, but not magic. Works great in some, but not all my cylinder bores. For instance, Rem Express 000buck works best in my Rem870 cylinder bore.