The Art Of Tank Warfare - Chris Keeling

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As the armor used on armored vehicles grew thicker and more advanced, it became obvious that smaller guns
were incapable of penetrating it. At first, this meant that the production of smaller guns ceased and the
production of larger guns increased. When the development of armor quickly outstripped the capabilities of
even the largest of the currently produced guns, new ammunition was designed to increase the penetrating
power of the guns already in use. Initially, the ordinary solid shot, or armor piercing (AP) round, was used
against tanks, while an ordinary high explosive (HE) shell was used against infantry and other ‘soft’ targets.
The problem with solid shot was that its penetrating power could only be increased through greater weight
that created an increase in the caliber of the gun, higher muzzle velocities, or increase in the chamber pressure
or barrel length. A ballistic cap (APCBC) could also be mounted in order to keep the shot from shattering
against thick armor. This problem was solved first by the Germans. By utilising a shell with a heavy
tungsten-carbide core, (APCR), surrounded with a softer metal and fired through a barrel which tapered as it
reached the muzzle, the softer metal would be squeezed from around the shot and as the barrel pressure
increased, so did the muzzle velocity of the round. An unfortunate side effect was a rapid drop-off in
velocity, which reduced the long-range performance of the round. A simplified version of this, called
discarding-sabot (APDS), used a lightweight collar that fitted around the tungsten carbide core, and dropped
off when fired. This had the advantage that it could be fired out of ordinary barrels and did not require a
tapering bore to maintain the higher barrel pressure.
For low velocity guns and rockets, another technological advance was required. This appeared in the form of
the shaped charge (HEAT), in which the explosive filler was moulded so as to leave a cone-shaped space in
the end facing the target. When the charge detonated, the concentration of explosive forces in that coneshaped
cavity created a solid jet of plasma (known as the Monroe Effect) capable of punching through armor.
This generally required a large warhead (at least 75mm) for good effect, but since the round was not
dependent on higher velocity for penetrating power, it could penetrate the same amount of armor at 1,000