I have been doing some research on this for a new gun. You also can find a good recap in the winter edition of Turkey & Turkey Hunting.

It seems that you may see some issues with the tighter constriction you are currently using. The various kinds use Tungsten? I believe whihc is very hard. As a result they seem to pattern better with less constriction.

I shoot the Winchester X-tended HD #5's through an Undertaker choke right now. I actually got good results with about 110 pelletes in 10 inch circle at 40 yds. This seems to match the results in the article I mentioned.

Pattern density in various loads and chokes was lower than this in most cases. The Winchester load is supposedly not as hard as some of the others and therefore was perhaps a better choice for the smaller constrictions.

The other interesting point whichI have only heard raised in this artcile was on ported chokes. One of these chokes features is to help seperate the wad from the load quicker. It was this particular authors question on wether these new heavy loads were designed to have the wad stay with the load longer to help keep pattern density further out. The ported choke tubes would arguably work against this and something to consider if yours is ported.

The new Federals are supposed to be the hardest so I am going to try these on the same set up I have now. That should give a good indication of this issue. With a .660 tube I would expect not as good performance with this harder load.

We'll see........