Patterning a shotgun isn't nearly as precise as sighting in a rifle. I'd shoot one shell at each distance and if everything looks good you are probably all set. Might want to shoot one or two more at the longer ranges just to make sure you first shot wasn't a fluke, but other then that you should be good to go. If you are noticing big holes in your pattern or the bulk of the pattern is hitting way off your point of aim, thats when i would start worrying about changing chokes and loads. I think you will find that most shotguns aren't as picky as rifles. Good luck!