RE: Choke/Ammo Combo for 870
With those loads you will probably end up on different ends of the choke size spectrum.
For instance with the Federal Flitecontrol shells I have always obtained better results with a more open choke (.690 all the way up to Imp. Cyl) that does not have "wad grabbers" integrated into the choke. Basically with the Flitecontrols you will want a choke that does not try to strip the wad away.
With the Winchester HV's I have gotten very nice results with a choke in the .650-.660 range.