20-mm Gun
NMUSN-5297: 20mm Anti-aircraft gun on display, 2018. This artifact has now been transferred to the Naval History and Heritage Command’s Curator Branch, Collection Management Facility, at Richmond, Virginia. Official National Museum of the U.S. Navy photograph Collection.
In 1940 the U.S. Navy searched for a light antiaircraft gun for shipboard defenses, its standard .50-caliber machine gun having proved totally inadequate. After much debate the Bureau of Ordnance purchased rights to the Swiss Oerlikon 20mm gun. As one Bureau of Ordnance officer said, “British experience with the Oerlikons at sea in November 1940 was uniformly excellent.”
The guns were successful against Japanese aircraft. From December 1941 to September 1944 the 20mm was credited with 32 percent of all Japanese aircraft kills by antiaircraft guns. In 1945, the Japanese began to emphasize suicide attacks, which rendered small-caliber antiaircraft fire nearly ineffective. The 20mm became more a morale booster than a defensive weapon. Fleet commanders began demanding that the larger 40mm guns replace the 20mm ones.
| Projectile Weight | 0.2174 pounds |
| Muzzle Velocity | 2.755 feet per second |
| Maximum Range | 4,800 yards |
| Rate of Fire | 850 rounds per minute |
This gun was on display in the museum's World War II exhibit, In Harm's Way. Transferred to the Naval History and Heritage Command’s Curator Branch, Collection Management Facility, at Richmond, Virginia, it will be cared for by the on-site staff as a rest period for the object.
NMUSN-5298: 20mm Anti-aircraft gun, 2023. This artifact awaiting to be transferred to the Naval History and Heritage Command’s Curator Branch, Collection Management Facility, at Richmond, Virginia. Official National Museum of the U.S. Navy photograph Collection.
NMUSN-382: In Harm’s Way Exhibit Area, late 1980s. This photograph shows the Torpedo Boat Area of the Pacific section, and the 20mm anti-aircraft gun. National Museum of the U.S. Navy Photograph Collection.
NMUSN-2744: 20 mm anti-aircraft gun. On display. National Museum of the U.S. Navy Photograph Collection.
NMUSN-4192: 20mm machine gun, early 1980s. Original is a negative color camera film strip. National Museum of the U.S. Navy Photograph Collection.
80-G-6691: USS Indiana (BB 58), an apprentice gunner gets his sights in a practice session with the anti-aircraft (20mm) batteries onboard the warship, during her commissioning ceremony, April 30, 1942. Official U.S. Navy Photograph, now in the collections of the National Archives.
80-G-324581: USS Bon Homme Richard (CV 31). U.S. Marines manning 20mm gun during snow storm at Bayonne, New Jersey. Photograph released January 7, 1945. Official U.S. Navy photograph, now in the collections of the National Archives. Note, the photograph is curved.
80-G-K-5790: 20mm Anti-aircraft Machine Guns Men firing from the flight deck galleries of an aircraft carrier, during a practice shoot, circa 1945.
80-G-375578: USS Hoggatt Bay (CVE-75). Shown: 20MM guns firing onboard. Photograph received June 3, 1946. Official U.S. Navy Photograph, now in the collections of the National Archives.
80-G-375580: USS Hoggatt Bay (CVE-75). Shown: 20MM guns firing onboard. Photograph received June 3, 1946. Official U.S. Navy Photograph, now in the collections of the National Archives.
