I've made perhaps 3-4 pounds of black powder. It's a chore.
There are a a couple of big safety concerns for myself.
The first is, black powder dust gets everywhere. It is unavoidable. This is why I do all work with it outdoors. I initially tried doing it in my garage, near the big door, but even then you could drag your finger along surfaces some feet away and find black powder dust on your finger. In its green meal state, it is as fine as talcum powder. The slightest disturbance sends it wafting about like smoke. Do this enough, and it's just a matter of time before many surfaces are covered in a fine dusting of black powder, and then some errant spark or flame will set it all off.
The second is pressing. I use a small aluminum (non sparking) cylinder with a 2" bore, followed by a 2" piston. I use this in an aluminum cookie sheet with a 12 ton press to press dampened green meal into cake/pucks.
The powder is damp, but not wet, and you do not want it wet or the potassium nitrate will leech out of the mixture. I haven't tried to burn any in this state, so I don't know what it would do. But it does make me quite on edge when cranking on what is essentially an aluminum grenade full of damp black powder with my 12 ton press. If it were to detonate, it would blow me in half, I am sure. I have toyed with the idea of using an air-powered hydraulic pump to operate the press remotely. And if I ever get back into the hobby seriously I will probably do that. In addition, it would probably be wise to devise a heavy steel blast deflector to mount to the press frame to direct the energy in a particular direction.
It's enticing because of the price. You can make a pound of black powder for around $5. But everything I've made has been rather dirty, to the point of fouling guns after a few shots. Unsuitable for competition use. On top of this I go through at least 25 pounds a year and I would have to do a lot of work to make that much powder.