Cutaway model of a 3,7cm H-Pzgr. (H stands for Hartkern / Hardcore), especially designed and manufactured for use in the Bk-3,7 (Bordkanone), in fact two 3,7cm Flak 18 anti aircraft guns, each packed in a container, and suspended under the wings of a Ju-87G, known as the ‘Kanonenvogel’ (Gunbird) or ‘Panzerknacker’ (Tank killer).
One of the major problems faced by the German army on the Eastern Front in WWII was the endless stream of Russian tanks, especially the T34 / 76, which immediately made the German tanks in use obsolete when it appeared on the battlefield. Even the anti tank guns in use could hardly knock out a T34. The weak spot of any tank however is the top and the backside, also with the T34. In Germany many Ju-87 Stuka’s were still available which were withdrawn from the western front when it appeared early in WW2 that the slow and sluggish stuka was a sitting duck for any fighter. On the eastern front however they were still used for close range frontline infantery support. There the idea to equip the Stuka with two Flak 18 guns was hatched in 1942, both guns placed in streamlined containers under the wings, forming a tankhunter.
The guns were renamed Bk-3,7 (Bk=Bordkanone / Aircraft gun). As the Stuka was a stable aircraft in flight it was possible to aim with great accuracy. Both guns had a 12 shot magazine and a firing rate of 160 Rpm.
Soon it occured that in the hands of a skilled pilot this new weapon could cause a slaughter among Russian armour. The ace Hans-Ulrich Rudel attacked a Russian motorcade in May 1942 and destroyed 18 tanks in just five minutes, for which he received the Iron Cross. On 29 December 1944 Rudel destroyed his 500th Russian tank on the eastern front, for which he was decorated by Hitler in person. In total Rudel had destroyed 519 tanks by the end of WW2.
The 3,7cm H-Pzgr. has an aluminium shell body in which a long tungsten carbide core is pressed in place. The nosecap is magnewin made (an alloy of magnesium with a small percentage of aluminium), which has an incendiary effect upon impact.
The shellcase is filled with a powdercharge that differs from the normal charge in the Flak 18 shells. It is loaded with 230 grams Nitrocellulose Rohrpulver (Nz.R.P) granular powder, 3mm long , 2,8mm in diameter and a hole of 0,5mm through. In the center of the powdercharge in the shellcase a small linnen bag is placed which contains 11 grams of rifle powder Nz.P. 1,5x1,5 mm, thick 0,75mm. The bag is fixated in the center position by a number of long tubular powder sticks (Nz streifen P), 230mm long with a diameter of 2mm and a 0,65mm hole through. This enshures the powdercharge is ignited mainly in the middle of the powdercharge, enshuring a high peak pressure which gives the projectile a high speed.
On top of the powdercharge a small roll of lead/tin wire is placed that forms an alloy with the copper of the driving band that remains in the barrel after each shot, thus forming a hard and brittle alloy, swept out of the barrel with the next shot.
Weight of the complete cartridge: 1290 grams
Projectile weight: 405 plm 8 grams
Length of the complete cartridge: 365mm
Length of shellcase: 264mm
Projectile length: 115mm
Diameter and length of the tungsten carbide penetrator: 16mm dia. x 85mm long
Vo: 1150 mtr/sec
Penetration against an armor plate with a 100 kg/mm2 yield strength:
140mm at 100m/90 deg
69mm at 100m/60 deg.
95mm at 600m/90 deg.
47mm at 600m/60 deg.
Regards, DJH
One of the major problems faced by the German army on the Eastern Front in WWII was the endless stream of Russian tanks, especially the T34 / 76, which immediately made the German tanks in use obsolete when it appeared on the battlefield. Even the anti tank guns in use could hardly knock out a T34. The weak spot of any tank however is the top and the backside, also with the T34. In Germany many Ju-87 Stuka’s were still available which were withdrawn from the western front when it appeared early in WW2 that the slow and sluggish stuka was a sitting duck for any fighter. On the eastern front however they were still used for close range frontline infantery support. There the idea to equip the Stuka with two Flak 18 guns was hatched in 1942, both guns placed in streamlined containers under the wings, forming a tankhunter.
The guns were renamed Bk-3,7 (Bk=Bordkanone / Aircraft gun). As the Stuka was a stable aircraft in flight it was possible to aim with great accuracy. Both guns had a 12 shot magazine and a firing rate of 160 Rpm.
Soon it occured that in the hands of a skilled pilot this new weapon could cause a slaughter among Russian armour. The ace Hans-Ulrich Rudel attacked a Russian motorcade in May 1942 and destroyed 18 tanks in just five minutes, for which he received the Iron Cross. On 29 December 1944 Rudel destroyed his 500th Russian tank on the eastern front, for which he was decorated by Hitler in person. In total Rudel had destroyed 519 tanks by the end of WW2.
The 3,7cm H-Pzgr. has an aluminium shell body in which a long tungsten carbide core is pressed in place. The nosecap is magnewin made (an alloy of magnesium with a small percentage of aluminium), which has an incendiary effect upon impact.
The shellcase is filled with a powdercharge that differs from the normal charge in the Flak 18 shells. It is loaded with 230 grams Nitrocellulose Rohrpulver (Nz.R.P) granular powder, 3mm long , 2,8mm in diameter and a hole of 0,5mm through. In the center of the powdercharge in the shellcase a small linnen bag is placed which contains 11 grams of rifle powder Nz.P. 1,5x1,5 mm, thick 0,75mm. The bag is fixated in the center position by a number of long tubular powder sticks (Nz streifen P), 230mm long with a diameter of 2mm and a 0,65mm hole through. This enshures the powdercharge is ignited mainly in the middle of the powdercharge, enshuring a high peak pressure which gives the projectile a high speed.
On top of the powdercharge a small roll of lead/tin wire is placed that forms an alloy with the copper of the driving band that remains in the barrel after each shot, thus forming a hard and brittle alloy, swept out of the barrel with the next shot.
Weight of the complete cartridge: 1290 grams
Projectile weight: 405 plm 8 grams
Length of the complete cartridge: 365mm
Length of shellcase: 264mm
Projectile length: 115mm
Diameter and length of the tungsten carbide penetrator: 16mm dia. x 85mm long
Vo: 1150 mtr/sec
Penetration against an armor plate with a 100 kg/mm2 yield strength:
140mm at 100m/90 deg
69mm at 100m/60 deg.
95mm at 600m/90 deg.
47mm at 600m/60 deg.
Regards, DJH
