Immediately after the appearance of armor protection of military equipment, the designers of artillery weapons began work on creating means that could effectively destroy it.
An ordinary projectile was not quite suitable for this purpose; its kinetic energy was not always enough to overcome the thick barrier of heavy-duty steel with manganese additives. The sharp tip creased, the case collapsed, and the effect turned out to be minimal, at best a deep dent.
Russian engineer and inventor S.O. Makarov developed the design of an armor-piercing projectile with a blunt front part. This technical solution provided a high level of pressure on the metal surface at the initial moment of contact, while the contact point was subjected to strong heating. The tip itself and the area of the armor that suffered the impact melted. The remaining part of the projectile penetrated into the fistula, producing destruction.
Feldfebel Nazarov did not possess theoretical knowledge of metal science and physics, but intuitively came to a very interesting design, which became the prototype of an effective class of artillery weapons. His sub-caliber projectile differed from the usual armor-piercing shell in its internal structure.
In 1912, Nazarov proposed the introduction of a solid rod inside a conventional ammunition, which is not inferior in its hardness to armor. The officials of the War Ministry dismissed the intrusive non-profit, considering that it was obvious that an illiterate retirement could not invent anything practical. Further events have clearly demonstrated the harmfulness of such arrogance.
The company Krupa received a patent for a sub-caliber projectile in 1913, on the eve of the war. However, the level of development of armored vehicles of the early XX century made it possible to dispense with special armor-piercing means. They were needed later, during the Second World War.
The principle of operation of a projectile is based on a simple formula known in the school physics course: the kinetic energy of a moving body is directly proportional to its mass and square of speed. Consequently, to ensure the greatest destructive ability, it is more important to disperse an attacking object than to weight it.
This simple theoretical position finds its practical confirmation. A 76-mm sub-caliber projectile is twice as light as a conventional armor-piercing projectile (3.02 and 6.5 kg, respectively). But to provide shock power is not enough just to reduce the mass. The armor, as the song says, is strong, and to break through it, additional tricks are needed.
If a steel block with a uniform internal structure hits a solid barrier, it will collapse. This process in slow motion looks like an initial collapse of the tip, an increase in the contact area, strong heating and spreading of molten metal around the point of contact.
Armor-piercing projectile works differently. Its steel case collapses upon impact, taking on part of the thermal energy and protecting the heavy-duty internal part from thermal destruction. The ceramic-metal core, having the shape of a slightly elongated bobbin for threads and a diameter three times smaller than the caliber, continues to move, punching a hole of a small diameter in the armor. At the same time, a large amount of heat is generated, which creates thermal imbalance, which, in combination with mechanical pressure, produces a destructive effect.
The hole, which is formed by a sub-caliber projectile, has the shape of a funnel expanding in the direction of its movement. He doesn’t need any striking elements, explosives and fuses, fragments of armor and core flying into the combat vehicle pose a mortal threat to the crew, and the heat generated can cause detonation of fuel and ammunition.
Despite the variety of anti-tank weapons, sub-caliber shells invented more than a century ago, still occupy their place in the arsenal of modern armies.