This is from 'hamkiller' -

'I had good sucess shooting T7 3f out of my Enfield Musketoon at a local trailwalk. I had developed a 3f black load of 42 grains for use at trailwalks shooting unsized Lee 500 grain traditional Minies and .575 sized Lyman Parker Hale 566 grain Minies. I loaded up a cartridge box full of both projectiles and taking into account the 15% greater power of T7 cut the charge to 35 grains of T7.

The course of fire was 30 rounds at targets mostly under 50 yds and the T7 rounds worked fine.
I could not tell difference in performance from black powder except no sulfur smell.'

You could do a lot worse than try, I'd guess.

tac