One of the most widely used naval weapons of World War II, the 20-mm Oerlikon antiaircraft cannon was installed aboard virtually every U.S. Navy warship—from lowly PT boats to massive battleships—as well as in auxiliaries and armed merchantmen. It could be bolted down almost anywhere, had a high rate of fire, and could come into action very quickly. More than 88,000 20-mm Oerlikons, in both single and twin mountings, were manufactured in the United States between 1941 and 1945. Another 30,000 were manufactured by the British for use in the Royal and Commonwealth navies.
Armaments & Innovations - The Instrumental Oerlikon
By Thomas Wildenberg