At the start of World War II, British fighters were equipped with Browning machine guns firing .303 ammunition. It was quickly apparent that these rounds were too light to ensure damage to Luftwaffe aircraft. The introduction of armour further reduced the effectiveness of the rounds and something with more ‘umph’ was a definite requirement. Luckily the British could turn to the Spanish designed Hispano Suiza HS.404 autocannon that could fire a 20mm round and ball, high explosive and armour piercing rounds were available. These rounds used a rimless brass cartridge casing that measured 110mm:
The base of the round has a deep extractor groove around its base to allow the spent casing to be pulled out of the breach of the cannon:
The base of the cartridge case indicates it was made in 1941 by BBC:
There is some debate about what the ‘BBC’ stands for. Some argue that it is Barking Brassware Company, however it seems more likely that these are the initials for the American company Bridgeport Brass Company from Connecticut which produced millions of these rounds for both the USA and the UK under lend lease.
These rounds saw extensive use throughout the war, with the Hispano cannons equipping Spitfires, Mosquitos and a myriad of different fighters. It was always a challenge to fit these cannon into an airframe as they were so much bigger than a Browning machine gun and the ammunition that could be carried was very limited. The guns had to be used sparingly to ensure the ammunition did not run out and the aircraft were under extreme stress when they fired. Despite these problems however, they gave British fighters the ‘punch’ they needed in the air.