John Adolphus Bernard Dahlgren (November 13, 1809 – July 12, 1870) was a United States Navy leader. He headed the Union Navy's ordnance department during the American Civil War and designed several different kinds of guns and cannons that were considered part of the reason the Union won the war. For these achievements, Dahlgren became known as the "father of American naval ordnance." He reached the rank of rear admiral.
Dahlgren was born on November 13, 1809 in Philadelphia, the son of Bernhard Ulrik Dahlgren, merchant and Swedish Consul in Philadelphia. He joined the United States Navy in 1826 as a midshipman and was promoted to the coastal survey in 1834. By 1847, he was an ordnance officer, and at the Washington Navy Yard began to improve and systematize the procurement and supply system for weapons.
He was assigned to the Washington Navy Yard in 1847. While there, Dahlgren established the U.S. Navy's Ordnance Department; became an ordnance expert; developed a percussion lock; and wrote a number of books, including The System of Boat Armaments in the United States Navy, Shells and Shell Guns, and Naval Percussion Locks and Primers. Under his command, the Navy established its own foundry, and its first product was the Boat Howitzer, which was designed to be used on both ship and in landings. But it is his cast iron muzzle loading cannon which came to bear his name (the Dahlgren gun) and be his most famous contribution. It was under his direction that the navy established its own foundry to manufacture new equipment.
His "shell gun" design was an improvement on the shell-gun invented by the French Admiral Henri-Joseph Paixhans. Dahlgren wrote:
The United States Navy had equipped several ships with 8-inch Paixhans guns of 63 and 55 cwt. in 1845, and later a 10-inch shell gun of 86 cwt. In 1854, the six Merrimack-class warships were equipped with 9-inch Dahlgren shell guns. By 1856, the Dahlgren gun had become the standard armament of the United States Navy.
The boat howitzer derived from a requirement realized during the Mexican-American War. During that war, naval landing parties were armed with a variety of army ordnance, often too heavy and cumbersome for use with the landing boats. Dahlgren first experimented with standard Army issue 12-pounder mountain howitzers before devising his own system of guns. The boat howitzers came in four basic types: small, light (or medium), and heavy versions of the 12-pounder and a larger 24-pounder. All conformed to the same basic shape, straight gun tubes with no adorning bands or clefts. Elevation was made via a screw threaded into the knob at the breech. Instead of by traditional trunnions, the guns were attached to the carriage by a loop under the barrel. The Dahlgren system also included mounting carriages that facilitated various employments of the guns. A single-axle metal carriage was designed for shore use. A bed-type carriage was used on small boats, with a rail system to allow the gun to be trained fore, aft and broadside of the boat. A similar mount was offered for shipboard use. The system of boat howitzers was used by the navy well into the 1890s, with some examples used in ceremonial purposes into the 20th Century.
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