I bought a specialized choke for Black Cloud and it didn't pattern any different than the factory IMP CYL Invector Plus. After a little investigation it would seem that the flight control wads used in Black Cloud holds the shot together like a slug and releases it well past the end of the barrel. Choking it in any way strips the wad and/or screws with the flight of the wad and ruins the pattern.
From what I have read the Blindside employs a similar design only with wing like peddles that deploy in flight to release the slot.
It would seem that specialized chokes for this type of shot is a bit of a marketing ploy and it certainly wouldn't be a good idea to use any type of wad stripping choke as it would defeat the purpose of the specialized wad. There have been some reports, that I can not confirm, of barrel damage using the some chokes with these.
The Blindside does have some interesting logic that went into its design and I am going to try some this season. I have had great results with #4 Black Cloud but the heavier shot not so much.
