| BK-5 cannon | |
|---|---|
rear view of a BK-5 in the National Museum of the United States Air Force, Dayton, Ohio, showing the semi-circular magazine |
|
| Type | Cannon |
| Place of origin | Germany |
| Service history | |
| In service | 1944–1945 |
| Wars | World War II |
| Production history | |
| Designer | Rheinmetall |
| Designed | 1943 |
| Manufacturer | Rheinmetall |
| Produced | 1943–1945 |
| Number built | approx. 300 |
| Specifications | |
| Weight | 540 kilograms (1,200 lb) |
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| Cartridge | 50 mm |
| Rate of fire | 45 rounds per minute. |
The Bordkanone 5, or BK 5 for short, was a 50 mm autocannon intended primarily for use against Allied heavy bombers, especially the USAAF's combat box heavy bomber flight formations, so that defending Luftwaffe fighter aircraft could fire from a great enough distance to make the USAAF bomber's heavy defensive firepower ineffective against defending German fighter aircraft. Rheinmetall was given a contract in 1943 to adapt the 50 mm KwK 39 tank gun, from the Panzer III tank, for aerial use in the twin-engined Me 410 Hornisse bomber destroyer. They were installed as Umrüst-Bausätze (Factory Modification) 4 in the Me 410A-1/U4, and experimentally, in two Me 262A-1a/U4 jet fighter prototypes (though these were not used operationally) [1], as the MK 214 cannon of similar caliber was not yet available. The semi-circular magazine held 22 rounds. Approximately 300 were produced and it saw only limited action, most notably in the Me 410A-1/U4 Hornissen aircraft that served with the II. Gruppe of Zerstörergeschwader 26. It was also mounted on the Junkers Ju 88P-4 night attack aircraft. Intended for long-range shots, the cannon was given a telescopic sight in addition to the Me 410's standard Revi C12C gunsight. This proved to be more of a hindrance than a help in the turning fights in which the Me 410s often found themselves, as the maneuvering targets easily escaped from the telescopic sight's small field of view[2].
As installed in the Me 262, the cannon was found to be prone to jamming, and if fired at night tended to temporarily blind the pilot's night vision.[1]
According to the account of the engagements against the USAAF by II/ZG 26 from late February through mid-April 1944 mentioned at a German language website [1], the 53 Hornissen of that Zerstörergruppe equipped with the BK 5 were said to have to shot down a staggering total of 129 B-17 Flying Fortress and four B-24 Liberator heavy bomber aircraft, distributed over a series of five or six interceptions, all while losing only nine of their own Me 410s.[2]