Here's something to ponder.

It was in AUSTRALIA that Holland & Holland found people
loading and shooting Double Rifles, but more importantly
BLACK POWDER Double Rifles, Bore Guns and Paradoxes

AND

Shoting them damn accurately.

So much so that I would guess that H&H used the interest here to rekindle manuafcture and development of DR's etc.

All credit to the old school in Australia who did this.