I just found this thread and realize I'm coming in pretty late to the discussion, but having recently purchased a 3566 Compact (356TSW caliber) semi-auto and looked for ammo to feed it, here's what I have found so far:
There have been several threads on this Forum about 356TSW ammo, so doing a bit of research here will pay off.
Yes, 356TSW ammo is still available as NOS (New Old Stock) on sites such as GB, primarily in Federal for FMJ ammo and Cor-Bon in SD rounds. I have also found that, for my semi-auto, 9 x 21mm FMJ ammo such as that made by Fiocchi works fine in my pistol, though it is nominally 1/2 a millimeter shorter than the design specs of 356TSW. You can find 9 x 21 ammo also on sites like GB but also it is still made, primarily by and for overseas markets in countries that don't permit civilians to own 9 x 19mm (Parabellum or Luger) because those are deemed military ammunition.
I also have read that the Magtech company produces 9 x 21mm ammo and sells it domestically, but I'm still trying to track that down.
I did not try shooting the 9 x 21 until some 356TSW owners reported they had shot it successfully, even with the shorter headspace of those rounds in their pistols.
As a side note, I'm not a revolver guy, but I understand that the Smith & Wesson revolver that was produced in 356TSW was known as the
Pocket Rocket, which I think is way cool...
