- "Deck gun" can also mean a type of big water nozzle used for firefighting.
The deck gun was used as a defensive weapon against smaller boats or ships and in certain cases where torpedo use was limited. Typically a crew of three; gunner, loader and layer, operated the gun, while others were tasked with supplying ammunition. A small locker box held a few 'ready-use' rounds. With a well-drilled, experienced crew, the rate of fire of a deck gun could be 15 to 18 aimed shots per minute.
The deck gun was introduced in all submarine forces prior to World War I. Although technically not a deck gun, USS Holland (SS-1), the first American submarine, was equipped with a pneumatic dynamite gun built into the bow in 1900. The deck gun was first used by the Germans in World War I, and proved its worth when the U-boat needed to conserve torpedoes or attack enemy vessels straggling behind a convoy. Submarine captains often considered the deck gun as their main weapon, using torpedoes only when necessary, since many World War I submarines carried 10 or fewer torpedoes. Lothar von Arnauld de la Perière used a deck gun on 171 of his 194 sinkings.
In early World War II, German submarine commanders favored the deck gun because of the unreliability of torpedoes. The deck gun became less effective as convoys became larger and better equipped, and merchant ships were armed. Surfacing also became dangerous in the vicinity of a convoy because of improvements in radar and direction finding. (See Defensively Equipped Merchant Ships [DEMS] and United States Navy Armed Guard). German U-boat deck guns were eventually removed on the order of the supreme commander of the U-boat Arm (BdU) during World War II. Some deck guns stayed on ships, but today they are no longer in use.
Two notable deck guns from German U-boats used in World War II were the 8.8 cm (3.5 in) SK C/35 (not to be confused with famous 8.8 cm Flak ) and the 10.5 cm (4.1 in) SK C/32. The 88 mm had ammunition that weighed about 30 lb (14 kg) and was of the projectile and cartridge type. It had the same controls on both sides of the gun so that the two crewman that were in charge of firing it could control it from either side. The 105 mm evolved from the 88 mm in the sense that it was more accurate and had more power due to the 51 lb (23 kg) ammunition it fired.
In the US Navy, deck guns were used through the end of World War II. Many targets in the Pacific War were sampans or other small vessels that were not worth a torpedo. The unreliability of the Mark 14 torpedo through mid-1943 also promoted the use of the deck gun. Most US submarines started the war with a single 3 inch (76 mm)/50 caliber deck gun, adopted in the 1930s to discourage commanders from engaging heavily-armed escorts. However, the aging S-boats were equipped with a 4 inch (102 mm)/50 caliber gun, which was often used to re-equip 3"-gunned submarines as the S-boats were transferred to training duties beginning in mid-1942. By 1944 most front-line submarines had been refitted with a 5 inch (127 mm)/25 caliber gun, and some were equipped with two 5 inch guns.
Japanese submarine cruisers used 14 cm/40 11th Year Type naval guns to shell California, British Columbia and Oregon during World War II. The 6"/53 caliber gun Mark 18 (152 mm) on the USS Argonaut, Narwhal and Nautilus (two per submarine), was the largest deck gun to be fitted on any United States submarine. The three British M-class submarines mounted a single 12 inch (305 mm)/40 caliber naval gun intended to be fired while the submarine was at periscope depth with the muzzle of the gun above water. This World War I design was found unworkable in trials because the submarine was required to surface to reload the gun, and problems arose when variable amounts of water entered the barrel prior to firing. The French submarine Surcouf was launched in 1929 with two 203mm/50 Modèle 1924 guns in a turret forward of the conning tower. The London Naval Treaty of 1930 restricted submarine guns to a maximum of 155 mm (6.1 inches).
In the Royal Navy, the Amphion-class submarine HMS Andrew was the last British submarine to be fitted with a deck gun (a QF 4 inch Mk XXIII). HMS Andrew was decommissioned in 1974. The last submarines in service in any navy to mount a deck gun were two of the four Abtao class submarines of the Peruvian Navy in 1999.
- uboat.net: The Deck guns
- Webber, Bert (1975). Retaliation: Japanese Attacks and Allied Countermeasures on the Pacific Coast in World War II. Oregon State University Press. pp. 14–16 & 40–62.
- Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. p. 132. ISBN 0-87021-459-4.
- le Masson, Henri (1969). The French Navy. Navies of the Second World War One. Garden City, New York: Doubleday and Company. p. 157.
- Akermann, Paul (2002), Encyclopedia of British Submarines 1901-1955, Periscope Publishing Limited, ISBN 1-904381-05-7 (pp. 426-427)
- Miller 2002, pp. 312–313
- Miller, David (2002). The Illustrated Directory of Submarines of the World. St. Paul, Minnesota: MBI Publishing Company. ISBN 0-7603-1345-8.