As an owner of several muzzle loaders myself I have fired most of them some time in the past, in the 1960's I applied for a black powder license and had a visit from a police officer. I can't remember exactly what he said but I think I would have to be a member of some club or another. Needless to say I didn't bother but simply used powder from fireworks.
Being able to buy fireworks all year round these days is a joke, one of my pistols could fire a lead ball and smash a brick to pieces and yet anyone can obtain all the means to fire a deadly weapon with evil intent.
Look at this one on the wall of my 'mancave' it's a 6ft long 19th century Arab musket that I have fired many times in the past, it's fishtail stock is made so you can fire one handed when galloping on a Camel!