 3"/50 caliber gun

The 3″/50 caliber gun (spoken "three-inch fifty-caliber") in United States naval gun terminology indicates the gun fired a projectile in diameter, and the barrel was 50 calibers long (barrel length is 3 in × 50 = ).Different guns (identified by Mark numbers) of this caliber were used by the U.S. Navy and U.S. Coast Guard from 1890 through the 1990s on a variety of combatant and transport ship classes.