Getting one of the H&R pardner single shot 20ga with screw in chokes as my back up gun. Can't decide which choke to get. I have Hevi-13 in the old 10 count box #6 along with the new #7. Do I get an IC in .555 or go to a .560 or .570 in a PureGold? They don't make a Jelleyhead that will fit but do make a tightwad. It comes with a 26" barrel. Thanks for your imput.