Echoes Of Tonkin

In “Anatomy of a Crisis” the main armament of our ships is given as “5 inch/.54 caliber” and “3 inch/.50 caliber.” There should be no decimal points in these descriptions. When discussing larger naval guns, the word caliber has two meanings. First, it refers to the diameter of the bore, here expressed in inches (5"); second, it refers to the ratio of the barrel’s length divided by bore diameter (54, a whole number, thus no decimal). The larger weapon should have been called a 5-inch/54-caliber gun. Multiplying the bore (5") by the number of calibers in the length results in 5"x 54=270 inches or 22.5 feet. Using the decimal number in the article results in a length (5"x.54) of 2.7 inches. Incidentally, the USS Iowa , one of our World War II battleships, which mounted the largest guns ever put on American vessels, had a main armament of 16-inch/50-caliber guns (16x50=800) so the barrel length was nearly 67 feet.