The pattern needs to be as dense as practical. Standard target loads have always worked best for me. If I was going to specialize in Magpie control, I'd choose a 12 ga with 1-1/8 oz handicap trap loads of hard 7-1/2's or 8's. Modified choke because they like to dipsey doodle when the shooting starts, range is not as much of an issue as putting the pattern on them. They are very challenging to hunt and to hit. Not fast, but quick direction changes.