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The Bordkanone 3,7 (BK 3,7) (on-board cannon 3.7) was a 3.7 cm (1.46 in) anti-tank/bomber autocannon based on the earlier 3.7 cm (1.46 in) Flak 18 made by Rheinmetall. It was mounted on World War II Luftwaffe aircraft such as the Junkers 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 fuselage of the aircraft as self-contained gun pods with 12-round magazines. It fired Armour Piercing Composite Rigid (APCR, Tungsten hard-core) ammunition or high-explosive shells in 37 × 263B mm caliber at 160 rounds per minute.
|Type||Aircraft mounted auto-cannon|
|Place of origin||Germany|
|Used by||Axis powers|
|Wars||World War II|
|Mass||295 kg (650 lb)|
|Length||3,630 mm (143 in)|
|Cartridge weight||APCR 380 g (13 oz), HE 640 g (23 oz), AT 685 g (24.2 oz)|
|Caliber||37 mm (1.46 in)|
|Rate of fire||160 rpm|
|Muzzle velocity||1,170–780 metres per second (3,800–2,600 ft/s)|
|Effective firing range||500 metres (550 yd)|
BK 3,7 equipped ground attack aircraft were developed for tank hunting on the Eastern Front in an effort to blunt the massive numerical superiority of the Soviet T-34 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 as Hans-Ulrich Rudel in his BK 3,7 armed Junkers Ju 87G.
The heavy-calibre auto-cannon-armed series of Junkers 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 only differed 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 previous method (bombs delivered by dive bombing), when the BK 3,7 was employed in a top attack profile against the especially thin upper turret and engine compartment armour of a tank, kills could be achieved with a relatively light and cheap armour-piercing projectile that could be carried in much greater quantities than bombs but would be insufficient to penetrate if fired horizontally from the ground in the normal method.
- BK 5 cannon : German 50 mm aircraft cannon
- BK 7,5 cannon : German 75 mm aircraft cannon
- COW 37 mm gun : earlier British equivalent
Weapons of comparable role, performance and eraEdit
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