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| BK 3,7 | |
|---|---|
 Hans-Ulrich Rudel'sJunkers Ju 87G, with twinBK 3,7 gun pods attached to the underside of the wings, in Russia 1943. | |
| Type | Aircraft mounted auto-cannon |
| Place of origin | Germany |
| Service history | |
| In service | 1942–1945 |
| Used by | Axis powers |
| Wars | World War II |
| Production history | |
| Manufacturer | Rheinmetall-Borsig |
| Specifications | |
| Mass | 295 kg (650 lb) |
| Length | 3,750 mm (12 ft 4 in) |
| Barrel length | 2,106 mm (6 ft 10.9 in) |
| Cartridge | 37×263mmB |
| Cartridge weight | (Shell only) APCR 405 g (14.3 oz) HE 640 g (23 oz) AT 680 g (24 oz) |
| Caliber | 37 mm (1.46 in) |
| Barrels | 1 |
| Action | Short recoil |
| Rate of fire | 160 rpm |
| Muzzle velocity | 1,140–800 metres per second (3,700–2,600 ft/s) |
| Effective firing range | 500 m (550 yd) |
TheBordkanone 3,7 (BK 3,7) ("on-board cannon 3.7") was a German 3.7 cm (1.46 in)anti-tank/bomberautocannon ofWorld War II and based on the earlier 3.7 cm (1.46 in)3.7 cm Flak 18 made byRheinmetall.
It was mounted onLuftwaffe aircraft such as theJunkers Ju 87 G-1 and G-2;Henschel Hs 129B-2/R3;Messerschmitt Bf 110G-2/R1-3;Junkers Ju 88P-2 or P-3 and others. The cannon could be attached under the wings or the fuselage of the aircraft as self-containedgun pods with 12-roundmagazines. It firedArmour Piercing Composite Rigid (APCR,Tungsten-cored) ammunition or high-explosiveshells at 160 rounds per minute.
BK 3,7 equippedground attack aircraft were developed for tank hunting on theEastern Front in an effort to blunt the massive numerical superiority of the SovietT-34 tank as the war turned against Germany. The concept was rather rudimentary, suffered from poor accuracy, severe weight penalty making the craft vulnerable to fighters, and low ammunition capacity; but could be extremely effective when operated by a sufficiently skilled and practised ground-attack pilot, such asHans-Ulrich Rudel in his BK 3,7 armedJunkers Ju 87G.
The heavy-calibre autocannon-armed series ofJunkers Ju 88P twin-engined attack–bomber destroyer aircraft series used twin BK 3,7 cannon, mounted side-by-side in a conformal ventral fuselage gun pod, in its Ju 88P-2 and P-3 versions. The P-3 version differed only through the addition of extra defensive armour. As with other examples of the P-series, the Ju 88P-2 and P-3 were perceived as failures as anti-tank and bomber destroyer aircraft.
In contrast to the bombs delivered bydive bombing, when the BK 3,7 was used to attack the relatively thin armour of the top of the turret and the engine compartment armour of a tank, kills could be achieved with a relatively light and cheaparmour-piercing projectile that could be carried in much greater quantities than bombs.
One of the two survivingJunkers Ju 87s is a G-2 model displayed at theRoyal Air Force Museum Cosford; the wings have attachment points for BK 3,7 gun pods but it is not displayed with them fitted.
