I have two WS-1 chokes, both in M12s. One has a 0.007 constriction and the other 0.010. Kind of tight to my mind. And then there's the bell.
Keep in mind that these chokes are 80+ year-old technology designed to work with cardboard and fiber wads on either end of the shot column. My understanding of the bell is that it allowed gas to bypass the shot column, thereby taking pressure off the wad column so that it would not blow through the pattern. One-piece plastic wads would make all that superfluous today.
I still think they're neat. I can be lazy about cleaning the barrel and the muzzle will still look clean, always void of that nasty plastic and lead striping.
