Friday 6 May 2016

World of Tanks History Section: Odd Grenades

Those who saw the movie "Saving Private Ryan" likely remember the unusual method with which American soldiers planned to defeat German tanks. They planned to destroy their track with "sticky bombs". This weapon could be made in several minutes from a soldier's sock stuffed with explosives and coated in grease. This bomb should stick to a tank if thrown. As one of the characters in the movie says: "Think of a better way to knock out the tracks, I'm all ears."

No one knows if a weapon like this ever destroyed a tank in real life, but both Great Britain and the USSR performed extensive experiments with sticky bombs.

Sticky, Soft, British

One of the first Britons to work on this subject was Millis Jefferis. In 1938, he started working on an anti-tank grenade for irregular warfare. His goal was to make a powerful anti-tank weapon that even poorly trained men could use. The weapon used the "squash head" principle, which dictates that the destructive effect of explosives increases if they are flattened against a flat surface. This is the same principle that drives HESH shells.

In his first experiments, the inventor used a resin based glue. Trials, however, showed that if the bombs stuck to metallic surfaces, it was purely by chance.

Meanwhile, the Second World War began, the Allies were beaten in France, and an effective anti-tank grenade was needed yesterday. Inventor Stuart Macrae joined in. Trials showed that so called "bird glue" used in bird traps performed best. Nitroglycerin with a thickening agent was chosen as the filler for the bombs. The resulting compound was similar to Vaseline in consistency.

The grenade was designed as follows. A light two-piece metal case was mounted on a handle. Pulling one pin made the hull fall apart, revealing a glass case. A second pin activated the trigger mechanism. Now the grenadier had to throw the grenade with such force that the glass would break and the filler stuck to the armour, at which point he would get away as far as possible: only five seconds elapsed between throwing the grenade and an explosion.

Winston Churchill personally took an interest in these grenades. In October of 1940, he made a note in his diary: "Sticky bombs. Make one million." However, trials that were taking place about this time did not cause excessive optimism. The grenade would not stick to the armour if it was wet or covered in even a thin layer of mud. Recall that being dirty is a tank's usual state.

Nevertheless, the "sticky bomb" was adopted by the British army under the name "grenade #74". 2.5 million were made before 1943.

Many were dissatisfied with the new grenade. One of them was Captain Gammon from the 1st Airborne Regiment. He proposed a simpler and more reliable explosive device. The "Gammon Bomb" consisted of an elastic fabric sack filled with plastic explosive. A detonator was located on top, under a metal cap. It was activated in mid-air by a fabric ribbon that freed a metal pin, like in some German or Soviet grenades.

This bomb was used mainly by paratroopers and other special forces. First of all, they had a lot of deficit plastic explosives. Second, they had many objects other than tanks in their path that made a good target for a serving of powerful explosives.

Another British grenade, "#75" or the Hawkins Grenade, seems ordinary by comparison. The rectangular device with a metal cap looked more like a canteen than a grenade. It could also be used like an anti-tank mine.

Soviet Experience

In late 1941, as a part of cooperation between the Allies, samples of British grenades were sent to the USSR. Soviet military specialists deemed them worthy of attention. The Nitrogen Institute began developing domestic sticky bombs.

On April 21st, 1942, at the proving grounds of the Stalin Armour Academy, dummy Soviet sticky bombs were tested, thrown at moving and stationary T-34 and T-26 tanks. Reports said that the bombs stuck to smooth vertical surfaces. If the surfaces were at an angle or dirty, the grenades slid off.

On June 15th, 1942, trials of "GIA anti-tank armour piercing grenades" began at the artillery proving grounds of the Middle Asia Military District. The tests were against 15 mm thick armour plates and a 14 mm thick tank turret. There was no full description, but the target was likely a blown apart T-26.

All tested grenades flawlessly stuck to the armour and blew up. 400 grams of explosive was enough to cave in 15 mm of armour. A 30 mm target was made for an 800 gram charge by leaning a 15 mm plate against the turret. The result was promising: a dent was made in the plate, the contact point between the turret and the plate was destroyed, and the turret itself was thrown off the turret ring and flipped over.

As the creator of the grenade, engineer Kalinin, wrote in his report, it was desirable to test the effect of the grenade on thicker armour plates or better yet, captured tanks. However, the Middle Asia Military District had neither.

The USSR had domestic grenades that could rival the sticky bomb if not in method of operation, then in sheer oddity. For example, in late 1941, factory #96 developed an anti-tank grenade using the KD liquid explosive (a mix of dichloroethane and nitric acid). Despite the savings that the inventors promised compared to TNT and regular grenades, the military treated this idea with scepticism, especially since experimental batches of grenades leaked in storage. Factory representatives made the excuse that the problem is in poorly made hulls and quality control should resolve it, but GAU officers understood that in the conditions of war, evacuation, and inexperienced workers (mostly women and teenagers), it is naive to hope for high quality. Soldiers at the front lines were already leery about picking up standard bottles of incendiary fluid, and one can imagine the popularity of a grenade that could start leaking acid at any moment.

Meanwhile, the era of HE anti-tank grenades was coming to an end in 1942. While these strange grenades were being tested on proving grounds, the next last-ditch weapon against tanks was already being tested: HEAT based hand grenades.

Original article available here.

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