One of the first things I did after putting up my plate a few years go was to test some spreaders ............... like tw, some were reloads and some were factory. I go through about two flats of the Fiocchis every six months, or so. I still pattern them in different guns from time to time, and have never seen any of those random fliers, way out of the pattern. But, I've never shot them at distance long enough to cause the fringe of the pattern to reach the plate edge. My spreaders are used at 20 yards or less. Further than that I have minimal confidence in their density, but they would probably be effective further. They buy me a little confidence on rabbit targets, or incoming birds at very close range, out of my M and M choked P gun.
The only time I ever used them at any distance, to speak of, was at the Fall Southern Classic, at Georgetown, one year. I was trying to qualify for the L C Smith team, using my 32" barreled 16 ga. LCS, choked .025" and .026". I bought a flat of Polywad SpredRs from Rick and used them on every target, close and far. I qualified with them, and shot in the LCS/Parker event, using them. I recall being impressed at how hard they broke some of the longish stuff.
SRH