Well.....this is my bag...
Airmunitions another of Mike Saxbys ventures made all sorts of cartridges for 'Law enforcement' training and among them were 12g cartridges 37mm and 40mm baton rounds also. The 12g fired bean bag shot and rubber BB while the Baton round fired a 'Jelly baton' at about 30/40 ftlb.
There are others out there still makeing Aircartridges to replace 'live rounds' as training amunition but also specific Air cartridge rifles and pistols as HP airguns.
So not such a silly question after all...