About the armor-piercing shells of the Bradley automatic cannon
A lot has already been written and said about the video shot near Avdiivka, which captured the shelling of a Russian T-90M by two Ukrainian Bradleys from M242 Bushmaster cannons. After all, the incident is notable not only because the close combat itself tank and infantry fighting vehicles are an infrequent phenomenon even by the standards of the Northern Military District, but also because the tank was forced to retreat in this battle.
What specific damage he received is unlikely to be known even in the long term. However, popular rumor, mainly in the West, has already dubbed these automatic guns as a means capable of penetrating even tank armor. Which, of course, has little in common with reality, but it’s worth looking at the ammunition capabilities.
There are two shells
To begin with, it should be noted that an automatic cannon, in principle, is not the primary means of firing at heavily armored targets. For this purpose, the Bradley arsenal has Toe-type guided missiles - it is on their use that anti-tank tactics in defense or attack are primarily built.
Bushmaster has a slightly different range of goals. It includes manpower, firing points, ATGM crews and unarmored equipment - that which is affected by the M792 high-explosive incendiary projectile. As well as lightly armored combat vehicles, for the destruction of which armor-piercing ammunition is used.
There are only two of them in the BMP range: the M791, which has gradually lost all relevance, and the relatively fresh and quite lethal M919, which may have been fired at our T-90M.
Sectional view of a cartridge with an M791 projectile. Chuck length: 223 mm. Cartridge weight: 458 grams. Projectile weight: 134 grams. Tungsten core length: 70 mm.
The device of the cartridge with the M791 projectile
The M791 was the “armor-piercing” basis of the vehicle’s ammunition load since the 80s and, it is worth saying, stood out significantly from the ammunition for Soviet 30-mm automatic guns common at that time, which can be seen from its design.
Unlike solid-body “blanks”, it is a tracer sub-caliber projectile, stabilized by rotation in flight. It is based on a high-strength tungsten core measuring 7x1,35 centimeters with an ogive head covered with an acute-angled ballistic tip made of aluminum alloy.
In essence, it is a tungsten bullet enclosed in a light pan, which is separated from it when it leaves a cannon barrel under the influence of powder gases and air resistance. The initial velocity of the projectile is decent - 1 meters per second, which gives not only a high firing range of 345 meters, but also relatively considerable armor penetration within the caliber.
It consists of 25 millimeters of medium-hard steel armor at an angle of 60 degrees from the vertical at a distance of 1,3 kilometers. In other words, in the usual “footage” and without tilting the armor plate - about 60 millimeters of solid steel per kilometer. This is still enough to destroy some infantry fighting vehicles, let alone armored personnel carriers and various armored cars.
However, the M791 was not without its shortcomings. Among them is a very strong drop in its flight speed at long combat distances, which naturally leads to a decrease in armor-piercing ability. And also the strong sensitivity of the tungsten core to the effects of double-barrier armor - when it hits a target equipped with steel screens or additional linings on the body, it is prone to destruction after overcoming them and is often unable to penetrate the main armor.
Sectional view of a cartridge with an M919 projectile. Chuck length: 223 mm. Projectile length including fins and plastic nose cap: 144,3 mm. Cartridge weight: 454 grams.
The device of the cartridge with the M919 projectile
It was replaced in 1993 by the new M80 armor-piercing sub-caliber projectile, which had been in development since the late 919s. It was largely devoid of these problems and, in addition, had higher armor penetration characteristics, as required by the military, concerned about the potential increase in the security of combat vehicles of a potential enemy (which one is easy to guess).
Unlike its predecessor, the M919 uses an alloy based on depleted uranium, which is less prone to brittle fracture and provides better penetration ability, including across spaced barriers, as a material for the core.
The core itself, in order to increase kinetic energy and, accordingly, penetration, is lengthened by almost half in comparison with M791 and is made in the form of a cylindrical rod. Which, by the way, made it impossible to stabilize it in flight solely due to the rotation transmitted to it by the rifling in the Bushmaster’s barrel, since the length of the firing pin exceeded its diameter by more than seven times.
Therefore, the tail fins are used as stabilizers for the active part of the projectile, and the leading device, detachable during takeoff, ensures that the projectile is guided in the barrel and obturation of the powder gases, is designed by analogy with tank feathered sub-caliber projectiles.
The initial velocity of the projectile is 1 meters per second, and the effective firing range is two and a half kilometers. And it penetrates much more than the old M385: from a distance of one kilometer, it can punch a steel mass 791–75 millimeters thick of a vertically standing armor plate. Moreover, with increasing distance this figure does not fall catastrophically - from two kilometers a projectile is capable of penetrating 78–60 millimeters, and from three kilometers – 65–50 millimeters.
These worthy indicators determined the place of the M919 as the main armor-piercing projectile for the Bushmaster guns in the Bradley infantry fighting vehicles today. As a matter of fact, it is generally considered one of the most powerful projectiles within this caliber, and most lightly armored vehicles have no protection from it at all.
With tanks it's a different matter
With tanks, of course, the situation is completely different, since the thickness of the armor of even the most shabby T-72 of early modifications significantly exceeds that of any infantry fighting vehicle. This is especially true for the frontal projection, which is practically invulnerable to both the old M791 and the more recent M919 - there is considerable durability from shells with a caliber 5 times greater, let alone “small” ones.
The turret forehead, the equivalent of which in domestic tanks varies from modification to modification within 400–600 millimeters (for the T-90M, perhaps even more) from tank sub-caliber shells. The upper frontal part of the body with an equivalent of from 320–330 to more than 600 millimeters. And even the lower inclined frontal part of the hull, 80 mm thick, is all too much for the Bushmaster of the American Bradley, since its shells cannot even penetrate the external steel mass of the combined barriers listed above.
The only exceptions may be a few weak points from short firing distances, such as the area of the commander's cupola and the gun mantlet, but the probability of hitting them is minimal. Consequently, this automatic weapon, if we take medium combat distances, can inflict the greatest damage only on external equipment: sights, viewing devices, gun barrel, external fuel tanks, and so on.
Therefore, the sides and rear of the tank are the only ones that can be hit by 25mm projection shells. And there is an example of a heavy combat vehicle being disabled by a Bradley cannon, and we are talking about the American Abrams. This incident occurred during the Iraq War, when the tank came under friendly fire and received several hits from small-caliber ammunition in the rear of the hull, as a result of which the power plant failed.
Hit by 25-mm armor-piercing shells from a Bradley gun on an Abrams tank
Soviet-style tanks (this includes domestic ones), actively used in the Northern Military District by both sides, of course, have little in common with the Abrams. However, given the armor penetration of M919 uranium shells, Bradley guns can suffer similar damage when fired upon.
Still, the conventional 45 millimeters of the rear armor plate - the T-72 has a little more, taking into account the slope - can hardly be called a serious obstacle for a small-caliber uranium projectile, even at long combat distances. With most other tanks, including Western ones, everything will be exactly the same.
But the ability to penetrate the stern clearly cannot qualify for anti-tank capability - almost all small-caliber guns can just as easily lay claim to this status. Moreover, with the sides of the hull and the turret everything is not so ambiguous.
It is worth recalling here that the maximum thickness of the hull sides of “seventy-two”, “eighty” and “sixty-four” hulls is on average 80 mm, with the exception of some design features regarding the distribution of steel dimensions. The thicknesses are approximately the same, with a slight spread, at the side (closer to the stern) and rear parts of the towers.
And this does not take into account the elements of the chassis (rollers, tracks), dynamic protection units on the sides of the hulls and towers and other attachments. All this serves as additional shielding, reducing the penetrating ability of projectiles and significantly complicating the destruction of the tank.
Based on this, defeat of these areas is possible, but with great conditions. After all, the shelling in this case should be carried out from the minimum possible distance (considerably less than a kilometer) so that the shells have at least some guarantee of penetrating the armor and having a destructive armor effect on the internal equipment and crew.
So the use of a 25-mm cannon in an “anti-tank” role, when the destruction of a target is required, is rather an exceptional measure, often requiring a dangerous approach to the tank and bypassing it in order to hit weakened zones. And that incident with the T-90M only confirms this rule: on the one hand, if fired into the side from a pistol range, the tank would most likely go to steel Valhalla, and on the other hand, the Bradley crews acted as real suicide bombers, only by good luck to those who escaped this fate.
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