T Ii E C A T K

Office Design Department to remove some shortcomings in De Wilde s design. However, such small projectiles are barely able to contain enough chemicals to make the effort worthwhile. The heavy machine gun is really the smallest calibre in which incendiary shells are common, with HE shells being more common in cannon (20 + mm) calibres. During the Second World War, it was discovered that adding aluminium dust to HE compounds not only improved the strength of the explosion but also had an incendiary effect. In consequence, pure incendiary cannon shells became less common.

One specialised form of HE projectile is the HEAT (high-explosive anti-tank) or shaped charge shell. In this, there is a cone-shaped hollow, lined with metal, left at the front of the shell. An instant-acting fuze detonates the HE on the surface of the target. The explosion compresses the metal

20x82 Ammunition


Ww2 Anti Tank Madsen

mm m

Ww2 Anti Tank Madsen
Second World War Cannon ShellsShaped Charge Exploding
Machine GunWwii Aircraft Fuze 151 Magazin

Sectioned German WW2 aircraft gun cartridges (from left to right): 20 X SORB HEIT-SD for MG-FF, 20 X SORB HE (M-Geschoss) for MG-FFM, 20 X 82 HEIT-SD for MG 151120. 20 X 82 HE (M-Geschoss) for MG 151/20, 20 X 82 APIHE (base fuze) for MG 151/20. Note differences between mechanical (1 and 2) and chemical (3) fuzes. Cartridge 4 is a practice round with a dummy fuze.

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lining to form an elongated high-velocity jet whose tip can be travelling at 8,000-9,000 m/s, with considerable armour-piercing capability. This type of projectile is standard in modern infantry anti-tank weapons and is used in some larger cannon. It was experimentally used in the Second World War in ammunition for German aircraft guns, but has not been generally used in smaller calibres because the effectiveness is largely determined by projectile diameter and is also lessened by being spun by barrel rifling. A rotation of only 150 revolutions per second is sufficient to reduce the penetration by 50%, yet a cannon shell will typically rotate at considerably more. In larger calibres, such as the Obus (named after the inventor, Gessner) for the French 105mm tank gun, this problem has been reduced by mounting the shaped charge on ball bearings within the case, greatly reducing the spin imparted to the explosive section, but this is not feasible with small-calibre ammunition.

However, the problem has been tackled by careful design of the shape of the HE cone and metal lining - generally a flatter cone is needed - and HEAT ammunition has quite recently become available for automatic cannon. Known as the M789 HEDP (HE dual purpose - anti-personnel as well as anti-armour), it is the standard type of ammunition used in the 30mm M230 chain gun fitted to the AH-64 Apache attack helicopter, in which the angle of the rifling has also been reduced to the minimum level needed to achieve stability. The M789 is capable of penetrating 50mm of steel as well as having a 4m lethal radius against unprotected personnel.

It should be noted that military terminology is not always logical. All projectiles for the 20mm Hispano, including AP, were officially referred to as 'shells' by the RAF.

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