A "5-inch gun" refers to a type of naval artillery with a caliber of 5 inches (127 mm). These guns are commonly used on warships for various purposes, including engaging surface targets, providing naval gunfire support, and defending against aircraft. They are known for their versatility and effectiveness in combat situations. Typically, 5-inch guns can fire different types of ammunition, such as high-explosive shells and guided projectiles. They are often mounted on modern naval vessels, including destroyers and cruisers, and are part of the armament systems that enhance the capabilities of the United States Navy and other naval forces worldwide.