I have had good results with Guilandi wads: a sort of combination post-X wad. I use them regularly. Patterns with an Ithaca 4E trap model (32" full) are spread to at least mod. I planned to run the results through Dr. Andrew Jones's shotgun insights pattern analysis program, but, as with a number of projects, haven't had time --- yet.
My theory of spreaders is that they must either mechanically disrupt the shot cloumn or dump some pressure into it at muzzle exit. Post wads use the post as a "storage vessel" of shot column pressure. As the shot passes through the choke, it drops intracolumn pressure and is less inclined to spring apart at muzzle exit. The wad post dumps some reserve pressure into the shot column and returns some of the spring apart. IMO, post spreaders should produce better patterns than mechanical disrupters.
DDA
