5"/25 caliber gun
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| 5"/25 caliber gun | |
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| Name | 5"/25 caliber gun |
| Origin | United States |
| Type | Naval gun |
| Service | 1930s–1960s |
| Used by | United States Navy |
| Wars | World War II, Korean War |
| Designer | United States Navy Bureau of Ordnance |
| Design date | 1920s–1930s |
| Manufacturer | Bethlehem Steel, Bangor-Pitts, Midvale Steel and Ordnance Company |
| Production date | 1920s–1940s |
| Number | Several hundred |
| Weight | Barrel and breech varied by mounting |
| Cartridge | 5 in (127 mm) |
| Caliber | 5 in |
| Caliber length | 25 calibers |
| Rate | Practical 8–12 rounds per minute |
| Velocity | ~2,100 ft/s (640 m/s) depending on charge |
| Range | Effective AA ceiling limited; surface range limited by low elevation |
5"/25 caliber gun
The 5"/25 caliber gun was a United States naval low-angle dual-purpose gun widely installed on United States Navy cruisers, destroyers, Battleship secondary batteries, and aircraft carrier hangar and island mounts prior to and during World War II. Designed in the interwar period by the United States Navy Bureau of Ordnance, the weapon prioritized anti-aircraft engagement at short ranges and close-in surface defense, influencing shipboard anti-aircraft doctrine adopted by the United States Navy and allied fleets during the Pacific War and early Korean War. Its compact size, relatively light weight, and simplified mounting allowed rapid installation in constrained superstructures across many United States Navy ship classes.
Design and specifications
The 5"/25 was a short-barreled (25 calibers) derivative of United States 5-inch naval guns, producing lower muzzle velocity and reduced maximum range compared with the longer 5"/38 and 5"/51 types. The design incorporated a monobloc barrel and semi-automatic breech mechanism developed under the supervision of the United States Navy Bureau of Ordnance and tested at Naval Proving Ground, Dahlgren and Indian Head, Maryland. It employed fixed or semi-fixed ammunition cases compatible with existing United States Navy logistics established after the Washington Naval Treaty era. Mountings allowed maximum elevations typically limited to 36°–50°, constraining ceiling against high-altitude aircraft compared with the later 5"/38 caliber gun. Manual and power-assisted training and elevation systems were used depending on the mounting supplied by contractors such as Bethlehem Steel and Midvale Steel and Ordnance Company.
Development and production
Development traces to interwar evaluations by the United States Navy Bureau of Ordnance seeking a compromise between dedicated anti-aircraft and secondary surface armament suitable for treaty-limited hulls like the Pensacola-class cruiser and Colorado-class battleship modernization efforts. Manufacturers including Bethlehem Steel, Bangor-Pitts, and Midvale Steel and Ordnance Company produced barrels and mount components under Navy contracts awarded in the late 1920s and 1930s. Production priorities shifted after the expansion of wartime shipbuilding overseen by the United States Maritime Commission and the Bureau of Ships, with many ship refits replacing 5"/25 installations with the more versatile 5"/38 caliber gun or augmenting close-in defenses with the 40 mm Bofors and 20 mm Oerlikon systems sourced through lend-lease adjustments and domestic manufacturing ramp-ups.
Operational history
The 5"/25 served aboard numerous United States Navy vessels during World War II, performing anti-aircraft and anti-destroyer duties in convoy escort, fleet screening, and amphibious support operations across the Atlantic Ocean and the Pacific Ocean. Its short barrel and lower muzzle velocity made it less effective in surface engagements at long range, but the gun proved useful for engaging low-flying aircraft, kamikaze attackers, and small craft during actions such as the Guadalcanal Campaign, the Battle of Leyte Gulf, and escort operations supporting Operation Torch follow-ons. As carrier and anti-aircraft doctrine evolved with improved fire-control systems from the Mark 37 Gun Fire Control System and radar suites like SG radar and SC radar, many 5"/25 mounts were supplanted by dual-purpose 5"/38 batteries to meet demands for effective medium-altitude defense.
Ammunition and fire control
The 5"/25 fired 5-inch (127 mm) fixed or semi-fixed ammunition with projectiles including armor-piercing (AP), high-explosive (HE), and training rounds developed within Naval Ammunition Depot specifications administered by the Bureau of Ordnance. Charges were scaled for the shorter barrel to optimize chamber pressure and muzzle velocity, producing typical velocities around 2,100 ft/s. Fire control initially relied on optical directors and predicting rangefinders such as those fielded by Mark 1 Fire Control System installations and later integrated with radar-directed control from Mark 37 Gun Fire Control System derivatives on modernized vessels. Proximity fuzes introduced during World War II improved anti-aircraft lethality, though many 5"/25 mounts retained older mechanical fuze setters until refits permitted modernization consistent with Ordnance Department logistics.
Variants and modifications
Variants included single and twin pedestal mountings tailored for specific ship classes, with field conversions executed during wartime refits to add splinter shields, power elevation, and remote control interfaces with centralized fire-control systems. Some vessels received removal of 5"/25 batteries in favor of additional anti-aircraft light weapons such as the Bofors 40 mm gun and Oerlikon 20 mm cannon, while others had 5"/25 mounts retained for close-in defense where space or stability limited installation of heavier dual-purpose mounts like the 5"/38 caliber gun. Experimental work during the late 1930s evaluated different chamber sizes and mounting shock absorbers in cooperation with industrial partners including Bethlehem Steel to reduce barrel wear and improve sustained fire.
Notable ship classes and deployments
The 5"/25 equipped numerous interwar and early-war United States Navy ship classes, including early Portland-class cruiser refits, some prewar Wickes-class destroyer conversions, and secondary batteries on Pennsylvania-class battleship modernization episodes. Escort carriers and auxiliary vessels also employed the gun where weight and deck space precluded larger dual-purpose mountings during Atlantic convoy duty and Pacific island operations. Installations aboard cruisers engaged in the Coral Sea and Solomon Islands campaign provided close-in anti-aircraft coverage until replaced or supplemented by the more capable 5"/38 caliber gun and radar-directed fire-control systems as wartime technological evolution accelerated.
Category:Naval artillery of the United States