Using a lanyard and stones suggest a weapon which would be more kin to the Fougasse weapon with the exception of using a barrel instead of digging a pit. This would be a different weapon than what is described as being used by Confederates at Vicksburg of filling a barrel with gunpowder lighting a fuse and rolling it downhill. While both weapons are called "Thunder barrels", but the destructive effects of each weapon would be quite different.