We very often say that you should go to a tighter exit diameter when you shoot smaller shot sizes...all things being equal. The problem is that it's not often that "all things are equal" with turkey chokes.
The most important part of a turkey choke is the interior of the choke, specifically the parts (dimensions/geometry) between the gas seal (breach end) and the muzzle end of the choke tube. It's really all about the angles and lengths of the conical section, the parallel section and any other specific treatments (lines, grooves, wad stoppers, etc.) of the choke, much more than about the specific exit diameter, which is only one part in the overall design of the choke.
We've learned so much in the last 12 years about how shot flows though a barrel and choke and in reality how little difference there is in that process for lead and tungsten-based shot. The buffering material or the wad will have more effect on how shot performs within the barrel and choke tube than the shot itself. There is of course a difference in the retained energy of shot types.
Good questions!
Thanks,
Clark
