I happened to read a book yesterday on pheasant hunting and it showed the effective ranges for each choke . Imp. cyl was 30 yards , Modified was 40 yards , and full choke was 50 yards . They went on to say beyond that the patterns would start to break-up to much .These were ranges to test pattern at to see what ypour shotgun would do ,not cast in stone that is what your shotgun would do .