Oerlikon 20 mm

Oerlikon 20 mm
Name	Oerlikon 20 mm
Origin	Switzerland
Type	Autocannon
Service	1930s–present
Designer	Oerlikon Contraves
Manufacturer	Oerlikon Contraves, Rheinmetall, Hispano-Suiza
Weight	variable
Length	variable
Cartridge	20×110mm, 20×128mm
Caliber	20 mm
Action	Blowback, recoil-operated
Rate	250–450 rpm
Velocity	830–835 m/s

Oerlikon 20 mm The Oerlikon 20 mm is a family of Swiss-designed autocannon developed in the interwar period and widely adopted for anti-aircraft and naval roles during World War II, the Cold War, and postwar conflicts. It influenced designs from Germany to Japan and saw service on warships, aircraft, and ground installations, with production under licence by firms such as Rheinmetall and Hispano-Suiza. The weapon's short recoil and blowback mechanisms, combined with compact ammunition, made it a staple in point-defense and close-range anti-aircraft systems across navies including Royal Navy, United States Navy, and Imperial Japanese Navy fleets.

Development and Design

Design work began at the Swiss firm Oerlikon Contraves under engineers connected to earlier projects at Becker (company) and influenced by patents tied to designers associated with Reinhold Becker and firms in Zürich. Early prototypes were trialed against requirements driven by naval experiences in the Spanish Civil War and tactical analyses from staff at Royal Navy and Bundeswehr predecessor organizations. The mechanism combined elements of existing autocannon in service with Luftwaffe and Regia Marina testing groups, while licensing arrangements were negotiated with industrial concerns in France, Italy, and United States ordnance bureaus. Adoption accelerated after sea trials with squadrons from Royal Netherlands Navy and reports forwarded to planners at the Admiralty and Bureau of Ordnance.

Variants and Models

Production spawned multiple variants to meet specifications from navies and air forces, including models chambered for 20×110mm and later 20×128mm cartridges requested by Bundesmarine and US Navy evaluators. Licensed manufacturers produced derivative systems dubbed by national services, with adaptations by Hispano-Suiza leading to comparisons against the HS.404 and alterations by Rheinmetall to suit NATO standardization efforts. Specialized twin and quadruple mounts were developed in cooperation with naval yards like Vickers-Armstrongs and Bethlehem Steel for integration aboard destroyers and escort carriers serving with Convoy HX and Pacific Theater fleets.

Technical Specifications

Typical specifications for single-barrel Oerlikon models include a caliber of 20 mm, barrel length varying by model, muzzle velocity around 830–835 m/s, and cyclic rates between 250 and 450 rounds per minute, figures comparable to contemporaneous designs from Mauser and Bofors (company). Operating mechanisms employed advanced blowback or advanced primer ignition recoil, concepts debated in ordnance committees in Paris and Washington, D.C.. The feed systems utilized 60- or 120-round drum magazines or linkless belt options specified by procurement offices in Ottawa and Canberra for coastal defense units affiliated with Royal Australian Navy.

Operational Use and Service History

The Oerlikon 20 mm saw extensive wartime employment aboard capital ships and escort vessels during World War II actions such as the Battle of the Atlantic and the Battle of Leyte Gulf, and postwar deployments in Korean War and Vietnam War contexts where navies from United Kingdom, United States, and France used them for close-in defense. Crews trained at establishments like HMS Excellent and facilities run by the United States Naval Academy learned maintenance procedures later codified in technical manuals issued by procurement agencies in London and Washington. Capture and reuse by axis and allied forces produced records in archives at institutions such as the Imperial War Museum and National Archives (United States).

Ammunition Types and Ballistics

Ammunition evolved from ball, tracer, and armor-piercing rounds to specialized high-explosive and incendiary projectiles requested by ordnance bureaux in Rome and Stockholm. Ballistic performance influenced tactical doctrine in reports circulated among staffs at Admiralty Research Establishment and Office of Naval Research, with effective engagement envelopes defined against aircraft such as Mitsubishi A6M and F6F Hellcat in after-action assessments. Later developments included proximity-fuzed and timed-fuze shells evaluated by committees linked to NATO and research groups at British Royal Armaments Research and Development Establishment.

Mounts, Fire-control and Integration

Mounting solutions ranged from simple pedestal installations used by coastal batteries overseen by Coast Artillery Corps (United States) to stabilized twin and multibarrel mountings integrated with radar directors from firms like Racal and fire-control systems developed by engineers with affiliations to Marconi Company. Integration work connected Oerlikon weapons to shipboard combat systems aboard vessels built by Blohm+Voss and Newport News Shipbuilding, and coordination with electro-mechanical predictors favored by staff at Directorate of Naval Ordnance in procurement cycles across Western Allies.

Legacy and Influence on Naval/AA Weaponry

The Oerlikon 20 mm influenced postwar close-in weapon system concepts pursued by programs at Raytheon and Thales Group, as lessons from service in engagements analyzed by historians at Naval War College and Imperial War Museum informed developments such as the Goalkeeper CIWS and lighter gatling systems adopted by Royal Netherlands Navy and United States Navy. Its widespread licensing and adaptation by firms like Rheinmetall and Hispano-Suiza established industrial precedents in standardization debates at NATO and production practices studied by analysts at Stockholm International Peace Research Institute.

Category:Autocannon Category:Naval artillery Category:World War II weapons