Monday, 11 January 2021

Red Army's First HEAT Grenades

Tanks became a true terror for infantry in WWI, although an "antidote" for these steel monsters was quickly found. The first stage was introduction of new ammunition for existing weapons: armour piercing bullets, rifle grenades, bombs, mines. Special anti-tank rifles and cannons were built later, but grenades and bottles with incendiary fluid became some of the most common weapons used against tanks.

Risking life

A Soviet tank destroyer squad at the start of the Great Patriotic War consisted of 2-3 men: 1-2 with Molotov cocktails and hand grenades, plus one with a submachine gun or machine gun. Vehicles could also be fought with a bundle of 3-5 fragmentation grenades tied together, although anti-tank grenades became the primary method for defeating enemy tanks.

A militia tank destroyer team, 1941.

The destructive power of the grenade depended on its explosive filler. The more explosives it contained, the more damage it could deal to armoured vehicles, but its mass increased as well. These grenades were thrown from cover at the tank's weakest areas: tracks, drive sprocket, engine deck, turret roof.

The Red Army used the RPG-40 grenade throughout the entire war. This 1.2 kg grenade could penetrate 20 mm of armour. The more powerful RPG-41 grenade weighed 2 kg and could penetrate 25 mm of armour. However, by 1942 the thickness of German tank armour exceeded the penetration offered by Soviet anti-tank grenades and their effectiveness decreased. Destruction of an enemy tank was a risky and difficult task for a grenadier.

"On October 2nd, 1942, 7 German tanks with submachine gunners attacked the front line of our defenses near the Red October factory in Stalingrad. Our forces were outnumbered. Red Armyman Panikako took grenades and bottles filled with KS fluid and headed for the lead tank. An enemy submachinegunner shattered one of his KS bottles and comrade Panikako burst into flame. Then, comrade Panikako jumped on the lead tank, burning it along with its crew. Comrade Panikako died the death of heroes."

A Red Army soldier with a bundle of grenades.

At the start of the war, the Military Council of the Western Front proposed a 1000 ruble reward for any soldier who destroyed an enemy tank, orders for destroying three, and a nomination for the title of Hero of the Soviet Union for ten. Towards the end of the war, anyone who "destroyed an enemy tank using grenades, incendiary bottles, or demolition charges oh the battlefield or in the enemy rear" was eligible for an Order of the Patriotic War 1st Class.

A Red Army soldier with RPG-40 grenades and incendiary bottles.

Early Soviet infantry anti-tank weapons posed a danger to their users, but design bureaus and research institutes were hard at work on improved anti-tank greandes.

GUF-800 impact HE grenade

In early 1942 the GAU considered two options for modernizing anti-tank grenades. One was proposed by factory #96: the PRG-KD grenade filled with a liquid explosive. The GAU was not satisfied with this proposal, largely due to issues with sealing the hull in storage.

Another more promising option was presented by factory #260: the GUF-800 impact HE grenade filled with 750 grams of cast TNT. It showed superior results during comparative trials held in the fall of 1941. Out of three hits on a captured tank, each one formed a breach that would have been fatal. The grenade was also easier to build (24 components compared to the RPG-40's 40). The commission recommended that a batch of 3000 grenades be produced by December 5th, 1941, and sent to the front for battlefield trials.

Proving grounds trials of the GUF-800 and PRG-KD were held at the Small Arms Scientific Research Institute Proving Grounds (NIPSVO) from May 20th to the 27th, 1942. Factory #260's grenade had an impact fuse and an oval hull filled with 730 g of cast TNT and a 45 g tetryl triggering charge. Even though the RPG-40 had more parts, it took 17.1 minutes longer to produce a GUF-800 grenade. The penetration was slightly higher than the RPG-40 (35 mm), but the grenade failed when thrown at soft soil (45% of the time) and snow (100% of the time). A repeat of the trials held on May 30th didn't give any better results. The GUF-800 failed proving grounds trials. Further work was deemed senseless.

GUF-800 grenade blueprint.

Factories #96 and #260 had no intention of giving up after having their ideas rejected by the GAU. The developers blamed insufficiently sensitive fuses for the failure and claimed that the trials conclusions were not objective. Their complaints were included in a letter to People's Commissar of Munitions B.L. Vannikov sent on June 25th, 1942, but it was too late. The fate of these projects was sealed, and by August work on directional HE grenades began.

"Comet" vs. a paper grenade

The future in anti-tank grenades was not hard to guess from the first paragraph of the summary of work by KB-30, a leading hand grenade developer, submitted on August 6th, 1942.
"To improve the penetration of handheld anti-tank grenades by raising the amount and quality of explosive filler is economically infeasible and reduces the maximum range at which they can be thrown by hand. The penetration can be improved by taking advantage of the directed effect caused by the geometric shape of the charge, its position relative to the plane of the armour, shape and size of the fuse, and other reasons."

Thus the USSR began working on its first HEAT grenades. KB-30 tested its prospective designs against 60 mm thick armour plates. The Artillery Committee sent out the tender for directional anti-tank grenades on August 26th, 1942. The battle for the honour of designing the Red Army's first HEAT grenade broke out between KB-30 and NII-6.

KB-30 developed the RPG-42 ND "Comet" directional grenade. The 280-285 mm long grenade weighed 950 grams, contained 600 grams of explosive. Variants with a fuse in the handle as well as a screw-on fuse were tested. KB-30's grenades were tested from October 15th to October 17th, 1942. Trials showed that the RPG-42 grenade was simple to produce, but its size and weight didn't match the blueprints, the quality of the explosive filler was low, the safety was unreliable, and the penetration varied between 45 and 55 mm. Subsequent trials with improved grenades held on October 19th-21st showed that the penetration was still insufficient: 45 mm if thrown and 55-60 mm if detonated statically. Despite this, the NIPSVO considered the grenade as having passed trials and recommended it for military trials.

Experimental HEAT grenade designed by KB-30, 1942.

NII-6 developed their own HEAT grenade. It was tested between October 30th and November 3rd, 1942. According to blueprints, the grenade weighed 1139 grams with a length of 373-375 mm. The fully assembled grenade was much longer than the RPG-42 (by 75-80 mm). The hull of the grenade was made from pulp, the handle was made from cartridge paper. The fuse was taken from a rifle grenade. TG or L mixes were used as explosive filler. The NII-6 grenade ended up being more complex than its competitor, but showed high reliability and penetration. After improvements, it was accepted for military trials.

NII-6 experimental grenade, 1942.

The NIPSVO also tested the RB-60 grenade produced by the People's Commissariat of Coal between November 15th and 16th. This attempt to jump on the bandwagon wailed. The conclusion was ruthless: "The proposed RB-60 grenade has no advantages over the KB-30 and NII-6 directional hand grenades".

RB-60 experimental grenade, 1942.

The subsequent flow of events is well known. Production of the KB-30 grenade under the name RPG-43 was approved after trials held in the spring of 1943. It turned out to penetrate up to 75 mm of armour. Production began in July. The importance of this grenade can be seen from the perks given to engineers and workers involved in its production. They were given additional rations, 200 g of tobacco per month, and were freed from any type of mobilization. The NII-6 grenade was also planned for production that year under the index RPG-6. The production version penetrated up to 100 mm of armour. RPG-40 production would finally cease.

RPG-43 grenade.

RPG-43 and RPG-6 grenades could be thrown from a trench or behind cover at a range of 15-20 meters. The grenade was stabilized in flight by several fabric ribbons. This allowed the grenade to impact the armour at a straight angle, dealing maximum damage. By the end of WWII 100-150 mm thick armour was not an unusual occurrence, and the GAU worked on developing grenades with even higher penetration. It was too early to announce the end of anti-tank hand grenades.

RPG-6 grenade.

After the war

The RPG-6 was removed from service in April of 1945 due to insufficient penetration. The RPG-43 remained in production after the war and remained in service until at least the mid-1950s. Even though the armour of tanks increased significantly, these cheap and effective anti-tank weapons were kept in service. The performance limits of HEAT hand grenades were not yet reached. The RKG-3 grenade developed by GSKB-30 was accepted into service by the early 1950s. The grenade weighed a bit over 1 kg but penetrated up to 220 mm of armour (in the RKG-3EM variant). This grenade remained in production for about 30 years and became the Soviet Army's last HEAT grenade.

RKG-3EM grenade and its carrying case.

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