The Hispano-Suiza HS.404 was a 20x110 mm aircraft autocannon designed by Hispano-Suiza and adapted into British Hispano and U.S. M1/AN-M2 cannon lineages. Public sources support its manufacturer, ammunition, and aircraft-armament relationships, while direct named-conflict use is left unattached without exact weapon-conflict evidence.
The record groups the original HS.404 design with British Hispano marks and U.S. M1/AN-M2 aircraft-gun models where public sources describe the same 20 mm Hispano cannon and ammunition lineage.
| Variant | Configuration | Designation notes |
|---|---|---|
| HS.404 | Original Hispano-Suiza aircraft cannon | Chinn treats the Birkigt Type 404 as a Hispano-Suiza 20 mm cannon chapter subject, while the RAF Historical Society describes the HS 404 as a mid-1930s Hispano-Suiza design observed by British officers in 1936. Sources: Chinn Machine Gun Volume I, RAF Historical Society Journal 45 |
| British Hispano Mk.I / Mk.II | British service and production lineage | Chinn says the original Birkigt Type 404 was used as the model for the British Mark I and was followed by the Mark II; Stoke-on-Trent Museums describes the British belt-feed development adopted in 1941 as the Hispano Mk.II. Sources: Chinn Machine Gun Volume I, Hispano Cannon |
| British Hispano Mk.V | Shortened and lightened late-war British lineage | The RAF Historical Society describes the late-war Mk.V as a shortened, lightened, faster-firing answer to the Hispano's length and weight, increasing from about 600 to 750 rpm. Sources: RAF Historical Society Journal 45 |
| M1 / AN-M2 | U.S. aircraft-gun models | War Department TM 9-227 covers the 20 mm Automatic Gun M1 and 20 mm Aircraft Automatic Gun AN-M2 as air-cooled aircraft weapons fed by drum magazine or disintegrating-link belt. Sources: War Department TM 9-227 |
The HS.404 family is documented with 20x110mm Hispano ammunition, including current HS404/HS804 loadings and historical aircraft loading imagery.
| Ammunition | Ammunition type | Firing evidence |
|---|---|---|
 | 20x110mm cannon ammunition | Ordtech lists 20x110mm ammunition for HS404 and HS804 cannons, while the museum reference gives 20 mm x 110 mm projectile context for the British Hispano Mk.II. Sources: 20X110mm ammunition, Hispano Cannon |
The HS.404 family moved from early drum-fed aircraft installations toward belt-fed British and American service models, which made the cannon more practical for wing and fuselage installations than a small in-flight drum supply.
Stoke-on-Trent Museums describes HS.404 drum magazines as limited to at most 60 rounds, with no practical in-flight magazine change in most aircraft installations.
The same museum account says British engineers developed a belt-feeding mechanism and that the modified design was adopted in 1941 as the Hispano Mk.II.
War Department TM 9-227 lists drum magazine and disintegrating-link belt feed for the M1 and AN-M2 aircraft-gun models.
Chinn identifies the Birkigt Type 404 as Hispano-Suiza's 20 mm cannon chapter subject, and RAF Historical Society material describes the HS 404 as a mid-1930s Hispano-Suiza design that impressed British observers in a 1936 firing demonstration.
Sources: Chinn Machine Gun Volume I, RAF Historical Society Journal 45
Heritage Gateway states that British rearmament led to a government shadow factory at Grantham for production of the 20 mm Hispano-Suiza aircraft cannon under the British Manufacturing and Research Company name.
Sources: Heritage Gateway BMARC Grantham
The Wikimedia Commons/IWM image metadata identifies a Bristol Beaufighter Mk VIF being re-armed at Honiley with belts of ball and high-explosive incendiary ammunition for four 20 mm Hispano cannon.
Sources: Wikimedia Commons Beaufighter Hispano Image
War Department TM 9-227 provided technical guidance for the 20 mm Automatic Gun M1 and 20 mm Aircraft Automatic Gun AN-M2, including identification, operation, feed, and ammunition data.
Sources: War Department TM 9-227
