Sorry Mike, can't let that one stand without comment!

The risk of chamber ringing is well recognized if a card wad is seated down on the powder column and a significant air-gap is created in the case between that wad and the base of the bullet.

If an appropriate filler is used to eliminate air gaps in the case, there is no risk of chamber ringing.

Read Graeme Wright's book "Shooting the British Double Rifle" which is the recognized authority on loading such cartridges.

Most of us on these forums have been loading Nitro-for-Black in our vintage doubles for decades without any issues whatsoever, using saddle-felt wads (my personal favorite), backer-rod, or kapok-style fillers.

A full Black Powder load will generate around 10 tons pressure, whereas most N-for-B loads are down around 7 or 8 tons pressure, making them kinder on vintage rifle actions.

So use BP loads for nostalgia or historical accuracy by all means, but don't discard N-for-B just because fools have ruined a few guns over the years.

...and yes, CJF, that's a beautiful old double by arguably the best maker at the time. Congratulations!