sentences:  By this time the Parrott rifle and newer, more powerful Columbiads like the Rodman gun were being introduced.These fired shells and shot that weighed between 10 and 300 pounds, though the Napoleons remained the most common field guns in Confederate hands.Later 12-pound cannons included the breechloading RBL 12-pounder 8 cwt Armstrong gun introduced in 1859, Joseph Whitworth's field guns and the boat howitzers invented by John A. Dahlgren and used by the Federal navy during the Civil War.