Isn't powder "contained" when it is in a barrel with a breech plug on one end & a ball on the other???Run a couple of stained pegs into the stone/ brick and go for it. By the way, hanging your horn off one of the pegs is PERFECTLY SAFE. A friend had a serious house fire and had several horns full of powder hanging with his rifles. When we went in to clean up the horns were found and of course the powder was gone. The horns had melted where the fire hit them and the powder burned, black powder uncontained, as in a rifle, DOES NOT EXPLODE.