it depends on how far you anticipate shooting. At room distances bird shot has not had time to dispurse and you get a thick pattern. Try 00 buck at about 30 yards and see what you get. number four is a much denser cloud even tho the individual pellets are not as heavy as 00, but you get more of them. There is a guy in the area here that does do a number on the chamber mouth of shotguns that makes them shoot longer5.
