Riprap,
One of my favorites in the field is a 20 ga M21 WS1/WS2. Most 20 ga WS1s mic about .003, maybe .004. WS2s I've measured are .010.
It's reasonable to wonder about the purpose of WS2, but consider: there were no shotcups when WS2 came into being, and skeet was a low-gun game (this means targets may well be hit after the stake).
I think WS1/WS2 is one of the great choke combinations, like IC/M. It is hard to beat for a grouse/WC gun.
Interestingly, in 12 ga guns WS1 typically runs about .008 or .009. WS2 runs just shy of .015. So, using shotcup loads one ends up with an IC/LM combination. The notion that 12 ga WS1 gets "patchy" beyond 20 yards is premised on the original intention of the choke and on available loads at the time. Pattern a few modern trap loads and you'll see why that idea no longer holds water.
Sam
