Yep ... They Work!
Official U.S. Navy photograph no. 80-G-K-14526

The USS Biloxi's 40-mm guns are test-fired during her shakedown cruise in October 1943. A Cleveland-class light cruiser, in 1944 she was primarily assigned to screen the carrier striking forces during their frequent attacks on Japanese-held islands and in the battles of the Philippine Sea in June 1944 and Leyte Gulf in October. She also used her guns to bombard enemy positions during the assaults on the Marshall Islands in January-February 1944 and Northern New Guinea in April.

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