5 cm KwK 39

History

The gun was developed as a variant of the 5 cm Pak 38 towed anti-tank gun using the same ammunition. On the Panzer III, it replaced the 5 cm KwK 38, which had an L/42 calibre length, less powerful ammunition and a lower muzzle velocity. However, even the 5 cm KwK 39 gun with a longer barrel, higher muzzle velocity and more penetration was not sufficient against newer Soviet T-34 and KV-1 tanks. Therefore, as time went on, the Panzer III was no longer effective as a medium tank that could engage in fights with enemy tanks.

So, a new role for the Panzer III tank was found. On the Panzer III, the 5 cm KwK 39 was phased out in favor of the shorter but larger calibre 7.5 cm KwK 37 L/24 low velocity guns that could fire more effective HE and HEAT rounds. HE howitzer type rounds with explosive forces and shrapnel were very effective against infantry, machine gun nests and towed enemy guns on the battlefield. However, early HEAT rounds were somewhat unreliable. They were useful against hardened fortifications and had a good, though limited, capability against enemy armour. Thus, they were used against enemy tanks mostly in an emergency. With these changes, the Panzer III with the 7.5 cm KwK became an infantry support tank late in its career, while the new, much more capable 7.5 cm KwK 40 L/43 was mounted on the larger Panzer IV Ausf. F2 (and the longer L/48 on subsequent Ausf. versions) to fight the KV and T-34 tanks.

Ammunition

Average penetration performance established against rolled homogenous steel armour plate laid back at 30° from the vertical. KwK 39 used shell 50×420 mm. R ;PzGr (Armour-piercing)

• Weight of projectile: 2.06 kg
• Muzzle velocity: 835 m/s

;PzGr. 39 (Armour-piercing, capped, ballistic cap)

• Weight of projectile: 2.06 kg
• Muzzle velocity: 835 m/s

PzGr. 40 (Armour-piercing, composite, rigid)

• Weight of projectile: 0.9 kg
• Muzzle velocity: 1180 m/s

;PzGr. 40/1 (Armour-piercing, composite, rigid)

• Weight of projectile: 1.06 kg
• Muzzle velocity: 1130 m/s

;5 cm Sprgr.Patr.38 (High explosive)

• Weight of projectile: 1.82 kg
• Muzzle velocity: 550 m/s

Vehicles mounted on

• Panzerkampfwagen III (Sd. Kfz. 141/1) Ausf. J to M (serial production). Several earlier models were re-equipped with this gun.
• Sd. Kfz. 234/2 - eight wheel armoured car

Aerial version

Bordkanone-series BK 5 heavy-caliber autocannon

References

References

1. Rottman, Gordon L.. (2008). "M3 Medium Tank Vs Panzer III: Kasserine Pass 1943". Osprey Publishing.
2. Rottman, Gordon L. p.4-5
3. "Munition der 5 cm Pak 38/KwK 39".
4. "Armor Penetration Table".
5. (2001). "WWII Ballistics: Armor and Gunnery". Overmatch Press.
6. "Germany's 50 mm Guns".