Remember, too, that the 25 yd definitional range for .410 patterns came about at a time when there were no shotcups. I don't know why we should be surprised to see greater pattern densities with modern ammo. After all, 12 ga Win full choke barrels often give almost 90% at 40 yds with best quality trap loads. Old WW catalogs suggest a mere 65 to 70%.
If you throw WW or RP 3" .410 shells through a full constriction at 25 yds you will likely do alot better than 70%. To be specific, I get an effective 20" circle at 40 yds with the RPs in #6 through my full choke M-42. By "effective" I mean something no phez could get through without 5 or more hits. At a more sensible 30 yds the WW load with #7.5 does the same on grouse/WC sized targets with this particular barrel.
That said, I prefer to use the mod choked guns in the field.
Sam
