Logo from Scott Cunningham.
Logo from Scott Cunningham.
he shaped charge (also known as the hollow charge) effect was well known for many years in the mining industry and was first described by C. E. Monroe in 1888, after whom it is sometimes named. Its effectiveness was greatly increased by lining the cavity with metal which was first done in Germany in the 1930s by F. R. Thomanck and led to the development of HEAT (high explosive anti-tank) ammunition.7 Shaped charges do not depend upon impact velocity for penetration, and will penetrate the same thickness even if merely placed upon a target. They were used in World War II by engineer units as demolition charges against obstacles and fortifications; as the warhead of infantry anti-tank weapons; and, less successfully, as an anti-tank projectile for some guns.
In a shaped charge the explosive is shaped into an inverted cone with an included angle typically of between 40° and 60°, with the base of the cone towards the front of the projectile. The inside of the cone is lined with a thin layer of metal, usually copper and typically about 2mm thick. At detonation the conical metal liner collapses onto the axis, forming a jet of the liner material which is ejected at high velocity out of the cavity. The jet elongates, increasing in velocity as it does so, and eventually breaks up. It is followed by a slug formed from the rest of the liner material but the latter moves at a much lower velocity and makes no significant contribution to the penetration of the target, which is due to the jet and in particular to its high velocity.7
A cutaway of an early German HEAT projectile, the Hl/A model. From Hogg’s German Artillery of World War Two..
Penetration depends upon the distance from the surface of the target, measured from the base of the cone, called the stand-off distance. It takes a certain amount of time for the jet to form, so if the stand-off distance is insufficient then the penetration will be less. Beyond a certain point, typically after 120 micro-seconds, the jet begins to break up and penetration decreases with a longer stand-off distance. There is an optimum stand-off distance which is far enough away to allow the jet to fully form, but not so far that the jet begins to break up, which produces a maximum penetration.7
The optimum stand-off distance for early shaped charges is about 2 cone diameters. The Germans were certainly aware of the effect of stand-off distance, as the original Gr. Hl design was soon replaced by the improved model Hl/A. This had a longer ogive to give a greater stand-off distance.10
Spin drastically reduces the penetration of a shaped charge.
Spin drastically reduces the penetration of a shaped charge. Further developments of German HEAT projectiles Gr. Hl/B and Hl/C incorporated several changes to counter the detrimental effects of spin on the formation of the jet, with only limited success.10 The best penetration that could be achieved by a spin-stabilised HEAT projectile in World War II was about 1.3 cone diameters, compared to about 2 cone diameters for a non-spinning projectile. The poor performance of spin-stabilised HEAT projectiles meant that they were mainly used for guns that had such a low muzzle velocity that conventional armour piercing shells had even less penetration, such as the German 7,5cm Kw.K.37, and howitzers of most nations.
Although the penetration of shaped charges can be considerable, this is not equivalent to the damage effect. The diameter of the hole created by the jet of a shaped charge is relatively small and decreases with depth of penetration. Consequently, even though a shaped charge may perforate thick armour, the diameter of the exit hole may be so small that it causes little, if any, damage behind the armour. The degree of damage may be equated with the size of the exit hole, which implies that there is a minimum diameter of the hole that needs to be created to achieve a particular level of damage.7
The lethality of World War II shaped charges was not particularly good…
The effectiveness of shaped charges is commonly described in terms of their residual penetration, that is the difference between theoretical maximum and actual penetration. The margin of performance for lethality has been variously put at 150mm to 200mm for modern projectiles.7 As this exceeds the penetration of many World War II shaped charges, it indicates that they are less damaging, or have less chance of totally knocking out a target than, say, a conventional armour piercing projectile with HE filler.
Shaped Charge Ammunition Part 2 The Stick Bomb
Do you like this web site? Please rate it between one and ten, with ten being the best:
Ratings are submitted to: The Wargames and Military History Search Engine.
