For over a century, the best anti-tank ammunition has been the fast-flying scrap. And the main question that gunsmiths are fighting over is how to disperse it as quickly as possible.
It's only in films about World War II that tanks explode after being hit by a shell - after all, it's a movie. In real life, most tanks die like infantrymen who have caught their bullet at full speed. An APCR projectile makes a small hole in the thick body, killing the crew with shards of the tank's armor. True, unlike the infantryman, most of these tanks can easily come back to life after a few days, or even hours. True, with a different crew.
In the modern reconstruction of the cannon with a tapered barrel, a characteristic detail is clearly visible: the shield is made up of two armor plates
Almost until the beginning of World War II, the speed of conventional field artillery shells was sufficient to penetrate the armor of any tanks, and the armor was mostly bulletproof. The classic armor-piercing projectile was a large steel blunt-pointed (so as not to slip off the armor and not break off the tip of the projectile) piercer, often with an aerodynamic copper cap-fairing and a small amount of explosives in the bottom - there were not enough reserves of their own armor in pre-war tanks for good fragmentation.
Everything changed on December 18, 1939, when, supporting the offensive of the Soviet infantry, an experienced KV-1 tank attacked the Finnish positions. The tank was hit by 43 artillery shells, but none of them pierced the armor. However, this debut was not noticed by experts for some unknown reason.
Therefore, the appearance at the front of Soviet tanks with anti-cannon armor - heavy KV and medium T-34 - was an unpleasant surprise for the generals of the Wehrmacht. In the very first days of the war, it became clear that all the anti-tank guns of the Wehrmacht and thousands of captured - British, French, Polish, Czech - were useless in the fight against KV tanks.
It should be noted that the German generals reacted quickly enough. Corps artillery was thrown against the KV - 10.5 cm cannons and 15 cm heavy howitzers. The most effective means of dealing with them were anti-aircraft guns of calibers 8, 8 and 10, 5 cm. In a few months, fundamentally new armor-piercing shells were created - sub-caliber and cumulative (in the then Soviet terminology - armor-burning).
Half-gun-half-gun
German 20/28-mm anti-tank rifle sPzB 41. Due to the conical barrel, which gave a high initial velocity to the projectile, it penetrated the armor of T-34 and KV tanks
Mass and speed
Let's leave the cumulative ammunition aside - we talked about them in the previous issues of "PM". Penetration of classic, kinetic projectiles depends on three factors - impact force, material and shape of the projectile. The impact force can be increased by increasing the mass of the projectile or its speed. The increase in mass while maintaining the caliber is permissible within very small limits, the speed can be increased by increasing the mass of the propellant charge and increasing the length of the barrel. Literally in the first months of the war, the walls of the barrels of anti-tank guns thickened, and the barrels themselves lengthened.
A simple increase in caliber was also not a panacea. The powerful anti-tank guns of the beginning of World War II were done basically like this: they took the swinging parts of anti-aircraft guns and put them on heavy carriages. So, in the USSR, on the basis of the swinging part of the B-34 ship anti-aircraft gun, a 100-mm BS-3 anti-tank gun with a warhead weight of 3, 65 tons was created.(For comparison: the German 3, 7-cm anti-tank gun weighed 480 kg). We even hesitated to call BS-3 an anti-tank gun and called it a field gun, before that there were no field guns in the Red Army, this is a pre-revolutionary term.
The Germans, on the basis of the 8.8 cm anti-aircraft gun "41", created two types of anti-tank guns weighing 4, 4-5 tons. On the basis of the 12.8-cm anti-aircraft gun, several samples of anti-tank guns were created with a very exorbitant weight of 8, 3-12, 2 tons. They required powerful tractors, and camouflage was difficult due to their large dimensions.
These guns were extremely expensive and were produced not in thousands, but in hundreds both in Germany and in the USSR. So, by May 1, 1945, the Red Army consisted of 403 units of 100-mm BS-3 cannons: 58 in corps artillery, 111 in army artillery and 234 in RVGK. And in the divisional artillery they were not at all.
The design of the shells allowed them to collapse in the bore
Forced cannons
Much more interesting was another way of solving the problem - while maintaining the caliber and mass of the projectile, accelerate it faster. Many different options were invented, but anti-tank guns with a tapered bore turned out to be a real masterpiece of engineering. Their barrels consisted of several alternating conical and cylindrical sections, and the projectiles had a special design of the leading part, allowing its diameter to decrease as the projectile moves along the channel. Thus, the most complete use of the pressure of the powder gases at the bottom of the projectile was ensured by reducing its cross-sectional area.
This ingenious solution was invented even before the First World War - the first patent for a gun with a tapered bore was received by the German Karl Ruff in 1903. Experiments with a tapered bore were also carried out in Russia. In 1905, engineer M. Druganov and General N. Rogovtsev proposed a patent for a gun with a tapered bore. And in 1940, prototypes of barrels with a conical channel were tested in the design bureau of the artillery plant No. 92 in Gorky. During the experiments, it was possible to obtain an initial speed of 965 m / s. However, V. G. Grabin was unable to cope with a number of technical and logical difficulties associated with the deformation of the projectile during the passage of the barrel bore, and to achieve the desired quality of the channel processing. Therefore, even before the start of World War II, the Main Artillery Directorate ordered the termination of experiments with barrels with a conical channel.
Gloomy genius
The Germans continued their experiments, and already in the first half of 1940, the heavy anti-tank rifle s. Pz. B.41 was adopted, the barrel of which had a caliber of 28 mm at the beginning of the channel, and 20 mm at the muzzle. The system was called a gun for bureaucratic reasons, but in fact it was a classic anti-tank gun with recoil devices and with a wheel drive, and we will call it a cannon. With an anti-tank gun, it was brought together only by the lack of guidance mechanisms. The gunner pointed the barrel manually. The gun could be taken apart. The fire could be conducted from wheels and bipods. For the airborne troops, a version of the gun, lightened up to 118 kg, was made. This gun did not have a shield, and light alloys were used in the construction of the carriage. The standard wheels were replaced with small rollers without any suspension. The weight of the gun in the firing position was only 229 kg, and the rate of fire was up to 30 rounds per minute.
The ammunition consisted of a sub-caliber projectile with a tungsten core and a fragmentation shell. Instead of the copper belts used in classic projectiles, both projectiles had two centering annular protrusions of soft iron, which, when fired, crumpled and cut into the rifling of the barrel bore. During the passage of the entire path of the projectile through the channel, the diameter of the annular protrusions decreased from 28 to 20 mm.
The fragmentation projectile had a very weak destructive effect and was intended exclusively for the self-defense of the crew. On the other hand, the initial velocity of the armor-piercing projectile was 1430 m / s (versus 762 m / s for the classic 3, 7 cm anti-tank guns), which puts the s. Pz. B.41 on a par with the best modern guns. For comparison, the world's best 120-mm German tank gun Rh120, mounted on the Leopard-2 and Abrams M1 tanks, accelerates a sub-caliber projectile to 1650 m / s.
By June 1, 1941, the troops had 183 s. Pz. B.41 guns, in the same summer they received their baptism of fire on the Eastern Front. In September 1943, the last s. Pz. B.41 cannon was delivered. The cost of one gun was 4520 Reichsmarks.
At close range, 2, 8/2-cm guns easily hit any medium tanks, and with a successful hit, they also put out of action heavy tanks of the KV and IS type.
Soviet 76/57 mm S-40 cannon with a cylindrical-conical bore
Greater caliber, lower speeds
In 1941, a 4, 2-cm anti-tank gun mod. 41 (4, 2 cm Pak 41) from Rheinmetall with a tapered bore. Its initial diameter was 40.3 mm, and its final diameter was 29 mm. In 1941, 27 4, 2-cm guns mod. 41, and in 1942 - another 286. The muzzle velocity of the armor-piercing projectile was 1265 m / s, and at a distance of 500 m it penetrated 72-mm armor at an angle of 30 °, and along the normal - 87-mm armor. The weight of the gun was 560 kg.
The most powerful serial anti-tank gun with a conical channel was the 7, 5 cm Pak 41. Its design was started by Krupp in 1939. In April – May 1942, the Krupp company released a batch of 150 products, which stopped their production. The initial velocity of the armor-piercing projectile was 1260 m / s, at a distance of 1 km, it pierced 145 mm armor at an angle of 30 ° and 177 mm along the normal, that is, the gun could fight all types of heavy tanks.
Short life
But if tapered barrels never became widespread, then these guns had serious shortcomings. Our experts considered the main of them to be the low survivability of the tapered barrel (on average about 500 shots), that is, almost ten times less than that of the 3.7-cm Pak 35/36 anti-tank gun. (The argument, by the way, is unconvincing - the probability of surviving for a light anti-tank gun that fired 100 shots at tanks did not exceed 20%. And not one survived up to 500 shots.) The second complaint is the weakness of fragmentation shells. But the gun is anti-tank.
Nevertheless, the German guns made an impression on the Soviet military, and immediately after the war, TsAKB (KB Grabin) and OKB-172 ("sharashka", where the prisoners worked) began work on domestic anti-tank guns with a tapered bore. On the basis of the captured gun 7, 5 cm PAK 41 with a cylindrical-conical barrel, TsAKB in 1946 began work on the 76/57-mm regimental anti-tank gun S-40 with a cylindrical-conical barrel. The barrel of the S-40 had a breech caliber of 76, 2 mm, and a muzzle - 57 mm. The full length of the barrel was about 5.4 m. The camora was borrowed from the 85-mm anti-aircraft gun of the 1939 model. Behind the chamber there was a conical rifled part of caliber 76, 2 mm, length 3264 mm with 32 grooves of constant steepness in 22 caliber. A nozzle with a cylindrical-conical channel is screwed onto the muzzle of the pipe. The weight of the system was 1824 kg, the rate of fire was up to 20 rds / min, and the initial speed of a 2, 45-kg armor-piercing projectile was 1332 m / s. Normally, at a distance of 1 km, the projectile pierced 230-mm armor, for such a caliber and gun weight it was a fantastic record!
The prototype of the S-40 cannon passed factory and field tests in 1947. The accuracy of the battle and the penetration of the armor-piercing shells of the S-40 was much better than that of the standard and experimental shells of the 57-mm ZIS-2 cannon that were tested in parallel, but the S-40 never entered service. The arguments of the opponents are the same: the technological complexity of making the barrel, low survivability, as well as the low efficiency of a fragmentation projectile. Well, besides, the then Minister of Armaments D. F. Ustinov fiercely hated Grabin and opposed the adoption of any of his artillery systems.
Conical nozzles
It is curious that the conical barrel was used not only in anti-tank guns, but also in anti-aircraft artillery, and in artillery of special power.
So, for the 24-cm long-range K.3 cannon, which was serially produced with a conventional bore, in 1942-1945 several more samples of conical barrels were created, on the creation of which the companies Krupp and Rheinmetall worked together. For firing from a conical barrel, a special 24/21-cm projectile weighing 126, 5 kg, equipped with 15 kg of explosives, was created.
The survivability of the first tapered barrel was low, and changing the barrels after several dozen shots was too expensive. Therefore, it was decided to replace the tapered barrel with a cylindrical-tapered one. They took a standard cylindrical barrel with fine grooves and equipped it with a conical nozzle weighing one ton, which was simply screwed onto the standard gun barrel.
During the firing, the survivability of the conical nozzle turned out to be about 150 shots, that is, higher than that of the Soviet 180-mm B-1 naval guns (with fine rifling). During the shooting in July 1944, an initial speed of 1130 m / s and a range of 50 km were obtained. Further tests also revealed that the projectiles that originally passed through such a cylindrical part are more stable in flight. These guns, together with their creators, were captured by Soviet troops in May 1945. Modification of the K.3 system with a cylindrical-conical barrel was carried out in 1945-1946 in the city of Semmerda (Thuringia) by a group of German designers under the leadership of Assmann.
By August 1943, Rheinmetall had manufactured a 15-cm GerKt 65F anti-aircraft gun with a tapered barrel and a swept-back projectile. A projectile with a speed of 1200 m / s made it possible to reach targets at an altitude of 18,000 km, where it flew for 25 seconds. However, the durability of the barrel in 86 shots put an end to the career of this wonderful gun - the consumption of shells in anti-aircraft artillery is simply monstrous.
Documentation for anti-aircraft guns with a conical barrel was transferred to the artillery and mortar group of the Ministry of Armament of the USSR, and in 1947, at the plant number 8 in Sverdlovsk, Soviet prototypes of anti-aircraft guns with a conical channel were created. The shell of the 85/57 mm KS-29 cannon had an initial velocity of 1500 m / s, and the shell of the 103/76 mm KS-24 cannon - 1300 m / s. For them, original ammunition was created (by the way, still classified).
The tests of the guns confirmed the German shortcomings - in particular, the low survivability, which put the final end to such guns. On the other hand, systems with a tapered barrel of 152–220 mm caliber before the appearance in 1957 of S-75 anti-aircraft missiles could be the only means of engaging high-altitude reconnaissance aircraft and single jet bombers - carriers of nuclear weapons. If, of course, we could get into them.
