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20mm TNSh Tank Gun

Usage:

Production tanks: T-40(T-30), T-60Sh.
Experimental tanks: T-38.

The beginning of war prompted the urgent need to arm light amphibious tanks with a small-calibre gun, because such a solution would allow it to be used both to fight infantry and as a mobile anti-tank weapon. As early as 5th July 1941, NKV instructed OKB No.15 to install the ShVAK gun into the turret of the T-40 tank. This task was solved at the first attempt by Nudel'man (who replaced Taubin in OKB No.16), rather than Shpital'ny, at the beginning of August. The test firings of the 20mm and 23mm guns from the mount developed at OKB No.16 were performed on 4th August. They showed positive results on the whole, but the guns themselves produced a number of failures (they often jammed). To finish this work, in accordance with the Order of the People's Commissar of Armament, the tank turret with the 20mm gun was sent to OKB No.15 where the purely artillery-related issues were worked on and where it was refined to its final design. The aircraft version of the ShVAK gun was used as the basis for the 20mm tank gun's design; its barrel was borrowed from the engine-installed version of the gun; the reloading mechanism - from the turret version of this gun; and the firing mechanism, sights, and back plate were designed from scratch.

In September 1941, as a replacement for the T-40, the Armed Forces accepted the T-60 Light Tank armed with the 12.7mm DShK machine-gun, just as its predecessor. In accordance with the combined decision of People's Commissar of Tank-Building Industry and People's Commissar of Armament, the tank was equipped with the experimental version of the 20mm gun designated "ShVAK-tankovaya" (ShVAK-for tanks). Nine days later it was accepted for service. Since 1st October 1941, the T-60 Light Tank was rearmed with this gun and accepted for service under the designation of T-60Sh. However, the tank gun performed badly and as a result, its production was extremely erratic until the winter. It was only on 5th December 1941, that the refined gun design was accepted for service under the designation of the TNSh (tank gun of Nudel'man - Shpital'nyj) and its production was started at Factory No.2.

In addition, the T-38 tank (nowadays it is exhibited at the Central Museum of Armed Forces) and the twin-turreted T-26 Light Tank were armed with the TNSh guns for experimental testing in the second half of October 1941. Besides, the T-30 and T-40 tanks earmarked for factory overhaul had been re-armed with this gun since January 1942.

Although the 20mm TNSh was theoretically similar to the German KwK 38 gun, in terms of its main performance characteristics, in practice its muzzle velocity turned out to be poor due to the use of cartridge cases with the powder charge of the 12.7mm machine-gun. The armour penetration capability of the gun, especially considering the use of the carbide tungsten core, was quite high; however, the behind-armour performance of the projectile was insufficient. Usually, the German tank, armoured car or armoured personnel carrier hit by a burst from the TNSh left the battle undamaged, if the core fragments did not hit either the fuel cells or the driver. The bursting performance of the round was also low.

SPECIFICATION
ParameterValue
Calibre, mm 20
Bore lenght, clb 82,4
Weight of pendulous elements, kg 68
Weight of recoil elements, kg ?
Normal recoil length, mm ?
Max recoil length, mm ?
Ammunition automatic, belt feed
Ballistic 20mm Aircraft Gun ShVAK
Practical ROF, shot/min 200
ARMOR PENETRATION
ProjectileAngleRange, m
50100300500
Armour-piercing 90° 35 28 22 15

Sources: "Artillerijskoe vooruzhenie sovetskih tankov 1940-1945" Armada-Vertical, No.4, 1999;
C.Grabin "Oruzhie Pobedy", 1987


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