As artillery began to develop (often faster than possible gun designs), many innovations were attempted. One such was The Polish Multi-Barrel Cannon from the 15th/16th Centuries. Comprised of 15 to 20 cast iron barrels, they were mounted in a triangular pattern. Identified today as a "volley gun", the weapon was not designed to fire simultaneously. Each barrel would be fired in succession. The theory here was to maintain a constant rate of fire. Often documented as being mounted on a carriage (similar to an artillery piece). Elevation was supposedly capable. The weapon fired 3 to 5 pound lead shells. Misfires and hang fires (shells that stop short in the barrel), were a common problem.