20 mm Hispano Mk II

20 mm Hispano Mk II
Name	20 mm Hispano Mk II
Origin	Spain
Type	Autocannon
Service	1930s–1950s
Used by	Spanish Republican Army, French Air Force, Royal Air Force, Royal Navy, Imperial Japanese Navy
Designer	Empresa Nacional Bazán
Manufacturer	Hispano-Suiza
Weight	43 kg (barrel and breech)
Length	2.08 m
Cartridge	20×110mm Hispano
Caliber	20 mm
Action	Short recoil, gas-assisted
Rate	700 rpm
Velocity	820 m/s
Feed	Belt

20 mm Hispano Mk II is a gas-operated 20 mm autocannon developed in the interwar period and widely used in World War II-era aircraft and naval applications. The design combined a high rate of fire with relatively light weight, making it attractive to aircraft manufacturers and naval planners across Spain, France, United Kingdom, Japan, and other states. The Hispano Mk II influenced subsequent autocannon families and saw adaptation across fighters, bombers, and naval mounts during key conflicts such as the Spanish Civil War, the Battle of Britain, and the Pacific War.

Development and Design

The Hispano Mk II traces its lineage to Hispano-Suiza engineers working in Barcelona and Madrid during the late 1920s and early 1930s, with technical input from designers linked to Empresa Nacional Bazán and other Spanish firms. Development occurred against the backdrop of the Great Depression and accelerating rearmament programs in France and the United Kingdom, where designers from Vickers-Armstrongs and Royal Aircraft Establishment monitored foreign autocannon advances. The Mk II adopted a short-recoil, gas-assisted mechanism inspired by earlier Hispano-Suiza automotive and aero engines, and its construction used techniques common to Vickers and Bofors designs of the era. Early trials involved prototype installations on types like the Hawker Hurricane and indigenous Spanish fighters evaluated during the Spanish Civil War.

Technical Specifications

The Hispano Mk II featured a 20 mm bore and a 20×110mm cartridge, with muzzle velocity typically around 820 m/s and a practical cyclic rate near 700 rounds per minute. The weapon’s breech and barrel assembly weighed approximately 43 kg, with a total installed length of about 2.08 m when fitted with standard recoil buffers. The feed system used disintegrating belts compatible with ammunition manufactured by firms such as Wellington, Société Française des Munitions, and Royal Ordnance. Mounting provisions allowed synchronization trials with propeller-driven aircraft like the Supermarine Spitfire and wing-root installations comparable to those used on De Havilland Mosquito prototypes. Materials and metallurgy reflected practices from Saint-Gobain and other European suppliers.

Operational History

Operational deployment began in Spanish service during the Spanish Civil War, where both Spanish Republican Army and Nationalist forces captured and reused examples. Export orders and license production placed the Hispano Mk II in French Air Force and Royal Air Force inventories prior to and during World War II. The cannon saw action in campaigns including the Battle of France and the Battle of Britain, fitted to fighters and night fighters alongside armaments from Hawker, Supermarine, and Bristol. In the Pacific War, examples fitted to naval and land-based aircraft encountered forces from the Imperial Japanese Navy and United States Navy in convoy and carrier actions. Postwar, surplus Hispano Mk II units influenced armament choices by air arms such as the Royal Canadian Air Force and navies modernizing destroyer and corvette close-in defenses.

Variants and Modifications

Manufacturers and users produced multiple variants and field modifications. Licensed production in France and United Kingdom led to local designations and parts interchange with Hispano-Suiza HS.404 development lines. Navalized versions incorporated water-cooling jackets and reinforced mounts for installation on Town-class destroyer and escort vessels similar to those operated by the Royal Navy and Free French Naval Forces. Aircraft installations were modified for wing-root, nose, and chin turrets on types such as Fairey Battle prototypes and carrier fighters operating from HMS Ark Royal. Postwar redesign efforts by firms like Dornier and Vickers-Armstrongs explored longer barrels and altered feed chutes to improve velocity and reliability.

Ammunition and Ballistics

Ammunition types standardized around the 20×110mm case included armor-piercing, high-explosive, and tracer rounds produced by manufacturers such as Société Française des Munitions, Royal Ordnance, and Spanish firms retooling after the Treaty of Versailles restrictions eased. Ballistic performance—muzzle velocity near 820 m/s and effective engagement ranges up to several hundred meters against aircraft—made the Mk II suitable for both air-to-air and air-to-surface roles. Terminal effects were studied by ballistic laboratories in Paris and London, influencing fuse selections and propellant charges used by artillery and naval ordnance bureaus in France and United Kingdom.

Users and Deployment

Primary users included the Spanish Republican Army, Spanish Nationalist faction forces (after capture and reuse), the French Air Force, the Royal Air Force, elements of the Imperial Japanese Navy, and postwar operators such as the Royal Canadian Air Force. Deployments spanned frontline fighters of Hawker, Supermarine, and Bristol manufacture, to naval mounts on destroyers escorting convoys for the Allies during the Battle of the Atlantic. In aviation, the cannon competed with contemporaries from Oerlikon and MG FF/M families and was selected where weight-to-firepower trade-offs favored the Hispano’s profile.

Legacy and Influence

The Hispano Mk II’s design informed later 20 mm autocannon such as the Hispano-Suiza HS.404 and influenced postwar developments by Bofors and Oerlikon. Its integration practices contributed to aircraft armament standards adopted by design bureaus at Supermarine, Vickers-Armstrongs, and Fairey Aviation Company, and naval adaptations presaged close-in weapon system thinking in navies like the Royal Navy and United States Navy. Surviving Mk II examples are preserved in collections at institutions including the Imperial War Museum and the Musée de l'Air et de l'Espace, serving as study pieces for historians of World War II ordnance and aerospace technology.

Category:Autocannons Category:Aircraft weapons Category:Naval artillery