I shot some of the 3" stuff that was factory testing samples, up at the Winchester plant in Alton, IL. I think the 3" can hold up to 5 defense discs. They are trying to decide how hot the new loads should be, whether they should use any shot in addition to the discs, etc.
VERY impressive is the 12 ga. PDX-1 with a one ounce slug and three OO Buck pellets!