The switch from existing calibres was not the result of a whim; rather, it was a carefully thought-out policy-one which has a long history. It was initiated by Stalin himself, a few hours before Germany's surprise attack on the USSR.
It was on the eve of the war that the Soviet naval and coastal artillery were first issued with the excellent 130mm gun. This was subsequently used as an anti-tank gun and as a field gun and finally, in a self-propelled variant. Also just before the war, in the spring of 1941, a highly successful rocket launcher was developed in the USSR. This was the BM-13, which could fire 16 130mm rockets simultaneously. It later became known to the Soviet Army as the `Katyusha' and to the Germans as the `Stalin Organ'. Naturally, the existence of both the gun and the rocket launcher were kept entirely secret.
In the first days of June 1941 the new rocket launcher was shown to members of the Politburo, in Stalin's presence. However, it was not fired, because artillery shells instead of rockets had been delivered to the test range. The mistake was understandable, in view of the great zeal with which secrecy was being preserved-how could the ordinance officers possibly have known of the existence of the 130mm rockets, which bore no resemblance to artillery shells?
Knowing Stalin, those present assumed that everyone responsible for this mistake would be shot immediately. However, Stalin told the Chekists not to get involved and went back to Moscow.
The second demonstration took place on 21 June at Solnechnogorsk. This time everything went off very well. Stalin was delighted with the rocket launcher. Then and there, on the range, he signed an order authorising its issue to the Soviet Army. However, he directed that henceforth, in order to avoid confusion, the rockets should be referred to as 132mm, not as 130mm.
Accordingly, while the rocket launcher continued to be known as the BM-13 (13cm being 130mm), the rockets were henceforth referred to, despite their true calibre, as 132mm. That very night the war began.
During the war, projectiles of all types were fired in enormous quantities, reaching astronomical totals. They were transported for thousands of kilometres, under constant enemy attack. While they were being moved they had to be trans-shipped again and again and this was done by schoolboys, by old peasants, by convicts from prisons and camps, by German prisoners and by Soviet soldiers who had only been in the army for two or three days. Orders and requisitions for the rockets were passed hastily by telephone from exchange to exchange and made all but inaudible by interference. But there were no mistakes. Everyone could understand that `We need 130s' was a reference to artillery shells and it was equally clear that `1–3–2 meant rockets.
In 1942 the design of the rockets was modernised and their grouping capability and destructive effect was improved. In the process, they became slightly thicker, and their calibre was increased to 132mm-thus coming to match their designation.
Stalin's decision had proved correct and, as a result, a series of artillery weapons with unusual calibres were developed during the war. They appeared, of course, only when an unusual shell or rocket was designed. For instance, in 1941 a start was made with the development of a huge mortar which was needed to fire a 40 kilogram bomb. The calibre of the mortar could have been, for instance, 152mm, like the great majority of Soviet guns and howitzers. Obviously, however, a howitzer shell would be unsuitable for a mortar and vice versa. A mortar fires a particular type of projectile, which must itself be of a certain calibre. This was the requirement which resulted in the development of the 160mm mortar. Immediately after the war, 40mm grenade launchers appeared. There had never before been a weapon of this particular calibre in the Soviet Army. There were 37mm and 45mm shells. But a grenade launcher uses its own type of projectile and a special calibre was therefore selected for it.
Soviet designers took steps to correct past mistakes, which had been tolerated until Stalin's sensible decision. The calibre of the standard Soviet infantry weapon is 7.62mm. In 1930, a 7.62mm `TT' pistol was brought into service, in addition to the existing rifles and machine-guns of this calibre. Although their calibre is the same, the rounds for this pistol cannot, of course, be used in either rifles or machine-guns.
In wartime, when everything is collapsing, when whole Armies and Groups of Armies find themselves encircled, when Guderian and his tank Army are charging around behind your own lines, when one division is fighting to the death for a small patch of ground, and others are taking to their heels at the first shot, when deafened switchboard operators, who have not slept for several nights, have to shout someone else's incomprehensible orders into telephones-in this sort of situation absolutely anything can happen. Imagine that, at a moment such as this, a division receives ten truckloads of 7.62mm cartridges. Suddenly, to his horror, the commander realises that the consignment consists entirely of pistol ammunition. There is nothing for his division's thousands of rifles and machine-guns and a quite unbelievable amount of ammunition for the few hundred pistols with which his officers are armed.
I do not know whether such a situation actually arose during the war, but once it was over the `TT' pistol-though not at all a bad weapon-was quickly withdrawn from service. The designers were told to produce a pistol with a different calibre. Since then Soviet pistols have all been of 9mm calibre. Why standardise calibres if this could result in fatally dangerous misunderstanding?
Ever since then, each time an entirely new type of projectile has been introduced, it has been given a new calibre. Naturally, shells for the BMP-1 gun are not suitable for the PT-76 tank-that was already obvious when work on the design of the new vehicle and of its armament was begun. Therefore it should not have a 76mm gun but something different-for instance, a 73mm one. The shells for the new T-62 tank were of a completely new design and would obviously not be suitable for use in the old 100mm tank guns. In that case, the calibre here too, should be something quite different-for instance, 115mm. The same went for the T-64 and T-72. Their shells had to be quite different from those of the old heavy tanks. So that the old and the new types of ammunition should not be mixed up, it was decided that the new shells should be 125mm whereas the old ones were 122mm. There are dozens of similar examples.
There are exceptions. In some cases it is essential to use a particular calibre and no other. For example, the 122mm, 40-barrel multiple rocket launcher must be of precisely that calibre-no more and no less. Its rockets are therefore given a special designation; they are called `Grad' rockets. This is the only way in which they are ever referred to-they are never called `122mm' rockets. One makes this a habit from one's very first day. Then, if someone orders `1–2–2 he is referring to howitzer shells, but if he orders `Grad', he means rockets.