page_title: QF 3-inch 20 cwt
section_title: Naval gun
hierarchical_section_title: QF 3-inch 20 cwt / Combat use / World War II / Naval gun
caption_attribution_description: English: &quot;submarine Life&quot;- Last Minute Duties Before a Mediterranean Patrol. March and April 1943, Malta, Officers and Men of a British Submarine Before Going Out on Patrol in the Mediterranean. Before the patrol - the gun is overhauled, cleaned and painted.
context_page_description: The QF 3 inch 20 cwt anti-aircraft gun became the standard anti-aircraft gun used in the home defence of the United Kingdom against German airships and bombers and on the Western Front in World War I. It was also common on British warships in World War I and submarines in World War II. 20 cwt referred to the weight of the barrel and breech, to differentiate it from other "3 inch" guns. While other AA guns also had a bore of 3 inches, the term "3 inch" was only ever used to identify this gun in the World War I era, and hence this is what writers are usually referring to by "3 inch AA gun".
context_section_description: In World War II the gun was carried by S-class, U-class and V-class submarines.
  It was also fitted to older destroyers, A-class to I class during refits in 1940, replacing a set of torpedo tubes, to increase their AA capabilities. Some smaller warships used this gun as well.  In 1939 it was estimated the RN had 553 Mk I, 184 Mk II, 27 Mk III and 111 Mk IV guns in service.
caption: On a U-class submarine, April 1943
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