Dahlgren guns were muzzle-loading naval artillery designed by Rear Admiral John A. Dahlgren USN (November 13, 1809 – July 12, 1870), mostly used in the period of the American Civil War. Dahlgren's design philosophy evolved from an accidental explosion in 1849 of a gun being tested for accuracy, killing a gunner. He believed a safer, more powerful naval cannon could be designed using more scientific design criteria. Dahlgren guns were designed with a smooth curved shape, equalizing strain and concentrating more weight of metal in the gun breech where the greatest pressure of expanding propellant gases needed to be met to keep the gun from bursting. Because of their rounded contours, Dahlgren guns were nicknamed "soda bottles", a shape which became their most identifiable characteristic. Dahlgren boat howitzers During the Mexican–American War the U.S. found itself lacking in light guns that could be fired from ships’ boats and landed to be used as light artillery in support of landing parties . Light artillery borrowed from the army proved unsatisfactory. In 1849, then-lieutenant Dahlgren began to design a family of smoothbore muzzle-loading boat howitzers that could be mounted in ships’ launches and cutters as well as being mounted onto field carriages. The first boat howitzers to be designed were a light "12-pounder", a heavy 12-pounder (originally designated a "medium"), and a "24-pounder". Later a lighter 12-pounder (the "small") and a rifled 12-pounder heavy howitzer were introduced. All of the boat howitzers were very similar in design, cast in bronze, with a mounting lug or loop on the bottom of the barrel instead of trunnions, and an elevating screw running through the cascabel. Having the single mounting lug expedited moving the howitzer from the launch to field carriage and back. In naval service the boat howitzers had gun crews of 10 in the boat and 11 ashore. The field carriage was made of wrought iron. No limber was used in naval service, but two ammunition boxes (each containing nine rounds) could be lashed to the axle of the field carriage. Members of the gun crew also carried a single round in an ammunition pouch. The smoothbore boat howitzers fired shell, shrapnel, and canister. The rifled 12-pounder fired shot and shell. Percussion primers were used in naval service, but the howitzers could also use friction primers obtained from the army. The small and the light 12-pounder boat howitzers were not popular. The heavy