Friday, 22 November 2013

World of Tanks: Today in History: D-25T Trials

During the Battle of Kursk in the fall of 1943, it was discovered that the 122 mm A-19 gun could effectively penetrate the German Tiger tank at any distance. Joseph Kotin, famous Soviet engineer, proposed the installation of this gun in the heavy IS tank, instead of the 85 mm D-5T.

The only possible way to do this in a short amount of time was to install a muzzle brake. This device allowed to place the gun on a universal mount without significant engineering effort. The military did not like the muzzle brake idea, as it would make the tank easier to detect. Furthermore, escaping gases were dangerous for the infantry that frequently rode on the tank. However, the People's Commissar of Tank Production, Malyshev, approved the IS with a 122 mm gun, since there was no other way to obtain a 122 mm gun quickly.

Initially, the D-25 had a screw breech, later replaced by a semi-automatic sliding breech. Various other changes were made: replacement of the muzzle brake, reinforcement of the recoil mechanism, increase of ammunition capacity to 30 rounds. After trials in 1943, it was decided that the 122 mm gun was powerful enough to destroy enemy tanks, artillery, and fortifications at large distances.

On November 21st, the D-25T with a new muzzle brake was tested against a Panther tank. The 122 mm blunt tipped shell could penetrate the 85 mm armour plate from 1200 meters. Considering that the tank burned, and was penetrated previously, this result was deemed inconclusive. Later, the new gun was tested on tanks in better condition, and a new shell was developed that could guarantee penetration at 1200-1300 meters.

The D-25T gun was powerful and effective. A downside was a low rate of fire due to an artillery type two-piece round, but the Red Army had no other alternative.

The IS, armed with a 122 mm gun, became the most powerful vehicle used by the Red Army. Breakthrough regiments used these tanks, immediately acquiring Guards status after formation. Due to the ability to penetrate any German tank at a large distance, German high command issued orders to avoid engaging these tanks.

The D-25T was also modified to be used on the ISU-122, under the index D-25S.

Original article available here.

Note: the article's assertion that two-piece ammunition leads to a lower rate of fire is not necessarily correct. Yes, the single piece IS-85 could fire faster than the two-piece IS-122, but single piece 122 mm ammunition used in the T-44-122 did not result in an increased rate of fire.

6 comments:

  1. Is there any document specifying the effectiveness of the A-19 during the Kursk battle? the data I have seen for KO Panther and Ferdinand does not have any 122mm impact.

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    1. Neither have I. I have a feeling that the amount of A-19s present at Kursk was very low.

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  2. Battle of Kursk in early July is considered to be the summer in most Western countries. Dates with years would be better as blunt tipped shell came after sharp nosed shell.

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  3. Regarding the speed of single vs. two piece ammo. I believe it depends on actual implementation(gun recoil) and user ergonomics (ammo storage, breech concept)... I believe the 122mm one piece ammo round was pretty long and nose heavy making it difficult to load quickly in T44 turret.
    Two piece ammo doesn't mean automatically a slow reload rate.

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  4. Low quality optics meant that, in reality, long distance combat ranges were seldom ever achieved by Soviet crews with any real consistency. Nor could the 122mm pen a PAnther's sloped armour above 600m. -- Russian Tanks of WW2: Stalin's Armored Might pg. 140

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    1. http://tankarchives.blogspot.ca/2013/07/birth-of-is-tanks-part-2-is-122.html

      The document I quote here gives a range of 1400 meters against the Panther. Svirin gives a range of over 1500 meters (at which the optics, like you say, make it difficult to aim). As Soviet optics improved and German armour degraded, the effective range became longer. Here you can find a quote from Malyshev reporting to Beria that the D-25 can destroy any German tank at a distance in excess of 1700 meters: http://tankarchives.blogspot.ca/2013/07/birth-of-is-tanks-part-3-is-100-and.html

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