What is the difference between a sub-caliber projectile and a conventional armor-piercing

Immediately after the appearance of armor protection of military equipment, artillery armament designers began work on the creation of means capable of effectively destroying it.

A conventional projectile for this purpose was not entirely suitable, its kinetic energy was not always sufficient to overcome the thick barrier of superalloy steel with manganese additives. The sharp tip crumpled, the body collapsed, and the effect was minimal, at best - a deep dent.

Russian engineer-inventor SO 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 surface of the metal at the initial moment of contact, and the place of impact was subjected to strong heating. The tip itself, and the area of the armor, which was subjected to a blow, also melted. The remaining part of the projectile penetrated into the resulting fistula, producing fractures.

Feldwebel Nazarov did not possess theoretical knowledge of metal science and physics, but he 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 with its internal structure.

In 1912, Nazarov offered to insert inside a conventional ammunition a solid core, which in its hardness is not inferior to the armor. Officials of the military ministry shrugged off the intrusive non-commissioner, having considered, obviously, that an illiterate retiree can not invent anything sensible. Further events clearly demonstrated the harmfulness of such arrogance.

The company Krupa received a patent for a sub-caliber projectile already in 1913, on the eve of the war. However, the level of development of armored vehicles of the beginning of the XX century allowed to dispense with special armor-piercing means. They were required later, during the Second World War.

The principle of the action of a subcaliber projectile is based on a simple formula known from the school course of physics: the kinetic energy of a moving body is directly proportional to its mass and the square of the velocity. Therefore, to ensure the greatest destructive ability, it is more important to disperse the damaging object than to weight it.

This simple theoretical situation finds its practical confirmation. The 76-millimeter sub-caliber projectile is twice as light as conventional armor-piercing (3.02 and 6.5 kg, respectively). But to provide shock power it is not enough just to reduce the mass. Armor, as it is sung in the song, is strong, and in order to break through it, additional tricks are needed.

If a steel bar with a uniform internal structure hits a solid barrier, it will collapse. This slow-motion process looks like an initial collapsing of the tip, an increase in the contact area, a strong heating and spreading of molten metal around the site of entry.

The armor-piercing sub-caliber projectile acts differently. Its steel body collapses when it strikes, taking over part of the thermal energy and protecting the heavy-duty inner part from thermal destruction. The metal-ceramic core, which has the form of a somewhat elongated bobbin for threads, and a diameter that is three times smaller than the caliber, continues to move, punching a small diameter hole in the armor. At the same time, a large amount of heat is released, which creates a thermal imbalance that produces a destructive effect in combination with mechanical pressure.

The hole, which is formed by a subcaliber projectile, has the shape of a funnel expanding in the direction of its motion. Defeating elements, explosives and fuels are not required for it, fragments of armor and core flying inside the combat vehicle pose a mortal threat to the crew, and the generated heat energy can cause detonation of fuel and ammunition.

Despite the diversity of anti-tank weapons, the sub-caliber projectiles invented over a century ago still occupy their place in the arsenal of modern armies.