One issue..zero load data anywhere. The website says blackpowder FFFg but no mention of how much. Not being a black powder guy, im kinda in the dark here.
I've shot lots of muzzle loaders with black powder. I would start with about 5 to 10 grains. I doubt you could blow this gun up even with the bore filled with black powder leaving just enough room to seat a ball, like the chambers of a cap and ball pistol.