I know what you are saying & believe you are correct but I'm afraid it won't help your case reguarding your collectible antique cartridge pistols.
In the earliest days of smokeless powder, one might argue, it was experimental. The powder was not proven science at that point nor were those who loaded it... or reloaded it... adequately knowledgeable to do so safely. Hense the cover your *** warning by Smith & Wesson.
Modern smokeless loads are now mature science. Cartridges are loaded within the pressure limits of the cartridge. Even antique pistols so chambered, in good condition, should be able to safely fire "standard" modern smokeless rounds. Many, many cartridges safely made the transition from BlackPowder to smokeless.
I don't think this would fly under US law, but I understand you are concerned with Austrailian law.
Best wishes!

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NRA LIFE
Reserve Officer 9yrs