Just back from patterning, Cartridge's I used were fiocchi f3 sporting 28g 7.5,fiocchi fblack 28g 7.5,gambore white gold 28g 7.5,eley superb 28g 8 and gambore evo 28g 8.
I shot one of each cartridge at 15 yards then measured the pattern width which supprisingly was around 17" on average apart...