Designed to fulfill the needs of battleships as well as destroyers, the 5-inch/38-caliber dual-purpose gun became one of World War II’s best regarded and most versatile naval weapons. It was the conflict’s iconic U.S. destroyer gun as well as the Navy’s workhorse on board capital ships, cruisers, and auxiliaries. Many more 5-inch/38s were made than any other World War II medium-caliber naval gun.
In the 1920s, the Navy used different guns to deal with aircraft and with surface targets. U.S. battleships and some destroyers were armed with high-velocity 5-inch/51s (the second number refers the length of the barrel in multiples of caliber; in this case, 5-inch caliber x 51 = 255-inch barrel). The gun was designed for use against unarmored destroyers, so its high velocity was not needed to penetrate armor. Rather it made for a flatter projectile trajectory, which could compensate for fire-control errors. The resulting long gun was somewhat unwieldy, and because it used bagged powder, the 5-inch/51 could not be loaded readily when the weapon was at high elevation.