"a barrel could easily lose direction or get stuck in the wrong place".

From the way I read the intented use of the Vicksburg weapon little direction or aiming would be required. Simply roll the thing downhill and let nature take its course, what happens, happens. I did not view that particular application as being intended to be a control detonation at a specific target. Unlike the intended use of the "Thunder Barrels" employed by Anderson at Fort Moultrie.