Sources give that the 6,6X70R was loaded by a charge of »Special Powder«; said powder possibly could be Spezial-Scheibenpulver from the „Pulverfabrik Hasloch a. Main“, which arrived on the scene around 1907/1908(maybe even 1906). It was noted as a unique powder that could be loaded by volume and didn't corrode the cases or more.
The Neumannswalde Testing Facility discovered that Hasloch Spezial Target Powder performed well for small kalibre target ammo loaded w/ copper jacketed bullets for „Schonzeit“ drillings or Kombos.
I now think I might know one reason why their Spezial-Scheibenpulver is not found so much in historical records and ammunition catalogues. After 1914 - the cartridge had hardly been introduced -, Haslach was under the aegis of the Military Economy (Kriegswirtschaft), and produced mainly propellants for war efforts. The factory was subordinate to the Bavarian Feldzeugmeisterei (Ordnance Department) until 1919.
https://www.deutsche-digitale-bibliothek.de/item/TE3WKUNUBTY2GLV6FXZZDNVEK3HW532MHardly had the Great War and the Kingdom of Bavaria ended in late 1918, and the interstice of the short-lived ultra-leftwing Bavarian Räterepublik been debellated in 1919 by the Freikorps,
https://en.wikipedia.org/wiki/Bavarian_Soviet_Republic(the citizens' militia, Einwohnerwehr Bayern, yielded their sole machinegun to the "defence" of the powder plant against the reds),
then the Great Inflation struck everybody hard until 1923.
And after the currency consolidation in 1924 and slow recuperation, two large explosions in 1926 and again in 1928 wrecked the factory and led to its final closure.
Carcano
