Reizstoff ammunition for German Police Gas Guns

[JoeW]

Dr. Lorenz Scheit's recent excellent book on German flare pistols and ammunition included a section on the German police Reizstoff (Irritant Gas) Pistole and ammunition.
Dr. Scheit displayed three cartridges in the ammunition section that conformed to the physical description of Reizstoff ammunition included in the Fischer book on German Police Weapons.

As I showed in the topic I wrote on the Reizstoff Pistol, the forward end of the bore past the depth of the standard Kal.4 flare round was reduced to 24mm diameter by means of a permanent barrel insert. I do not understand how a tear gas round that looks like a standard flare pistol round would function in a barrel in which the diameter is reduced by 2.5mm. Would something from the cartridge be blocked when firing?

The description of the police gas gun specifies that only Type A ammunition that was suitable for attacking closed rooms would function in the Reizstoff pistol. The other Type B ammo would function in a standard flare pistol. To me this indicates that a projectile of small diameter was shot from the standard size casing for the gas cartridge. Scheit also includes in his book a photo of such a cartridge by CFS Hamburg along with a box.

Does anyone has an identified Type A German Police Gas Gun cartridge? Do I mis-understand the design of this pistol?