I shot one back in the day - 1970's. I don't remember much about it, other than it wasn't very accurate. The fellow
was not using the proper mould, as he used the mould for his Zouave, the Lyman #574213 I think it was, the 505gr. I do remember it didn't kick much but
I don't know how much powder he loaded. My .54 kicks harder.
I shoot 55gr. 3F in my .54 with round ball in my flintlock pistol. Not much muzzle flash. No more or at least not much more it seems, than a rifle produces.
Lots at night, though.