5"/25 caliber gun

The 5"/25 caliber gun (spoken "five-inch-twenty-five-caliber") entered service as the standard heavy anti-aircraft (AA) gun for United States Washington Naval Treaty cruisers commissioned in the 1920s and 1930s. The goal of the 5"/25 design was to produce a heavy AA gun that was light enough to be rapidly trained manually The gun was also mounted on pre-World War II battleships and aircraft carriers until replaced by the standard dual-purpose 5"/38 caliber gun, which was derived from the 5"/25 and was similar except for the barrel length. United States naval gun terminology indicates the gun fired a projectile 5 inches (127 mm) in diameter, and the barrel was 25 calibers long (that is, for a 5" bore and a barrel length of 25 calibers, 5" x 25 = 125", or about 3.2 meters).

History
The gun weighed about 2 metric tons and used fixed ammunition (case and projectile handled as a single assembled unit) with a 9.6-pound (4.4 kg) charge of smokeless powder to give a 54-pound (24 kg) projectile a velocity of 2100 feet per second (640 m/s). Ceiling was 27400 ft at the maximum elevation of 85 degrees. Useful life expectancy was 4260 effective full charges (EFC) per barrel. The short barrel of the 5"/25 made it much easier to train manually against fast-moving targets. These guns were manually controlled so the short barrel and light weight made it an early favorite as an anti-aircraft gun. Another key feature was power loading, allowing rapid fire at high elevation angles. The 5"/38 caliber gun replaced the 5"/25 as the anti-aircraft weapon of choice on new construction by the mid-1930s due to its better range, velocity against surface targets, and higher vertical ceiling.

5"/25 guns removed from pre-war battleships (especially those rebuilt after Pearl Harbor) had their barrel linings chromed. These guns then began being mounted on submarines in late 1943 for extra firepower against small boats and sampans often encountered off the coast of Japan and elsewhere in the Pacific Theater, replacing the earlier 3-inch and 4-inch guns. The Mark 17 gun in the Mark 40 submarine gun mount used semi-fixed ammunition (case and projectile handled separately) and had a range of 14500 yd at the maximum elevation of 40 degrees. The submarine mounting had manual elevation, train, and loading with no power assist.

Ships mounting 5"/25 caliber guns

 * USS Pensacola (CA-24)
 * USS Salt Lake City (CA-25)
 * USS Northampton (CA-26)
 * USS Chester (CA-27)
 * USS Louisville (CA-28)
 * USS Chicago (CA-29)
 * USS Houston (CA-30)
 * USS Augusta (CA-31)
 * USS New Orleans (CA-32)
 * USS Portland (CA-33)
 * USS Astoria (CA-34)
 * USS Indianapolis (CA-35)
 * USS Minneapolis (CA-36)
 * USS Tuscaloosa (CA-37)
 * USS San Francisco (CA-38)
 * USS Quincy (CA-39)
 * USS Brooklyn (CL-40)
 * USS Philadelphia (CL-41)
 * USS Savannah (CL-42)
 * USS Nashville (CL-43)
 * USS Vincennes (CA-44)
 * USS Phoenix (CL-46)
 * USS Boise (CL-47)
 * USS Honolulu (CL-48)
 * USS Lexington (CV-2)
 * USS Saratoga (CV-3)
 * USS Ranger (CV-4)
 * USS Nevada (BB-36)
 * USS Oklahoma (BB-37)
 * USS Pennsylvania (BB-38)
 * USS Arizona (BB-39)
 * USS New Mexico (BB-40)
 * USS Mississippi (BB-41)
 * USS Idaho (BB-42)
 * USS Tennessee (BB-43)
 * USS California (BB-44)
 * USS Colorado (BB-45)
 * USS Maryland (BB-46)
 * USS West Virginia (BB-48)
 * Balao class submarines
 * Tench class submarines