40 mm and 20 mm machine guns firing during the shakedown cruise of the U.S. Navy light cruiser USS <i>Biloxi</i> (CL-80), October 1943. Note the 40 mm gun crew keeping their weapons loaded with ammunition. Also note the gun pointer protecting his ears, as the mount operates under director control.
U.S. Navy
Official U.S. Navy photo <a rel="nofollow" class="external text" href="https://www.history.navy.mil/our-collections/photography/numerical-list-of-images/nhhc-series/nh-series/80-G-K-02000/80-G-K-2843.html">80-G-K-2843</a> from the U.S. Navy <a rel="nofollow" class="external text" href="http://www.history.navy.mil">Naval History and Heritage Command</a>