Tuesday, 23 April 2013

Soviet 107 mm Guns

Even before WWII, before the Tigers and Panthers, before the Ferdinands and Maus tanks, the rumours of the next super-armoured and super-powerful heavy tank were floating around. Whether it was the Neubaufahrzeug, B1, or some other menace from a potential enemy, the USSR had to be able to defend against it. 107 mm was the caliber of choice, perhaps due to the already available 107 mm field gun model 1910, modernized in 1930. However, even before the war, this gun was deemed not powerful enough, and a new 107 mm gun model 1940 was built. The length of the gun increased, from 38 calibers to 43. However, this was still a field gun, unsuitable for installation in a tank.

In 1941, during a phone call to Stalin, Grabin expressed the need for "a powerful tank gun, capable of penetrating armour of the tank that carries it at 1000 meters". Stalin suggested that the gun should be even more powerful than the modernized 107 mm gun. The 107 mm tank gun ZiS-6 was produced in only 38 days. Another 107 mm gun was considered, the F-42, but it was too bulky to install in even the KV-2's roomy turret. However, several parts of its aiming and loading mechanism were borrowed for the ZiS-6.

But that's not the most powerful gun of that caliber that was built. In 1938, a gun of unprecedented power was ordered. 107 mm in caliber, 70 calibers in length, capable of penetrating a 160 mm armoured plate sloped at 30 degrees, from a kilometer away! All this, at 10 rounds per minute.

Let's see how all of these guns fared.

CAMD RF 38-11355-10

The table above demonstrates calculated penetration data against an armoured plate at 1000 meters, angled at 30 degrees from horizonal. The rows that interest us are in the middle.

The 107 mm gun model 1910/30 penetrates a respectable 81 mm at this distance. Even this was enough to defeat the armour of any German tank in 1941. The upgraded model 1940 gun (M-60) penetrates a more impressive 100 mm. This is enough to take out a Tiger from the front, a whole two years before a Tiger was even built. The ZiS-6 gun lives up to its promise of being able to penetrate its own tank's armour at 1000 meters (this gun was meant for the rather beefy KV-3 tank), with 115 mm of penetration. The "107 mm high power gun (experimental)" achieves 188 mm of penetration. That's enough to pierce a Tiger tank front to back! 

There was also another 107 mm gun project, the M-75, an upgrade over the M-60, just a year after it was built. Mounted on the ML-20 carriage, it could penetrate 165 mm at 30 degrees, at 1000 meters. That one didn't make it in time for the chart above, but it exists in another document.

CAMD RF 81-12038-50

When the war started, Germany turned out to not have any super-powered monsters in its arsenal at all. Instead of making overpowered guns that could penetrate the strongest enemy armour 3 times over, the USSR focused on making cheaper guns, for lighter tanks. The KV-3, KV-4, and KV-5 programs were shut down, and the 107 mm high power guns went with them. 

8 comments:

  1. I also know that 107 mm guns had excellent ballistic performance (penetration drop over distance), comparable or even actually better than the Germans' guns.

    So an L/70 would likely penetrate about 140 mm at 2 kilometers and 120-130 mm at 3 kilometers, both against armor angled at 30 degrees, calculating from the penetration table of M-60.

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    1. I also believe that the L/70 would destroy Tiger frontally from 4 kilometers away, considering its excellent ballistics performance.

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  2. So KV-5 could had 188mm of pen, and if they were produced could easily roflstomp Tigers in war.

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    1. If there were Tigers in 1941, you'd have seen KV-3s rolled out in the same year, and KV-4/5s the year after.

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  3. If produce, KV-5 would be utterly useless, kinda like the maus. Too heavy, consume too much fuel manpower and material, unable to cross bridges, and probably breakdown every few miles.

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  4. Yes, but 100 tonne and 188 tonne is still a huge difference. If I had to pick one of them, I would choose KV-5 over Maus, at least KV-5 wouldn't have to crawl at 8 km/h.

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    1. The KV-5 would have been great as commanding tanks

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  5. The key word in this document is "calaculated performance".
    The performance tabulated is reasonable for the soviet blunt nosed APBC shells. However, the caveate lies in the projectile technology itselfe.
    The calculated data are reasonable for intact penetrators and apply as long as the shell doesn´t bend, upset, break or compress against the plate.

    Soviet period AP shells were, however, made from low alloy steel, which suffered by poor hardenability, and generally did not receive AP-caps.
    Consequently, they were very soft and unable to survive the stresses of high velocity impact intact. Breaking up reulted in a loss of penetration performance compared to calculated values.

    Trials conducted 1941 with high performance 107mm ATG and soviet domestic shell seem to support this, as the long barreled gun was struggling to penetrate 152mm vertical RHA at 200m with the projectiles breaking up.

    These high powered guns would still penetrate a lot of armour downrange, when the impact velocity dropped sufficiently. But AP-performance would tend to plateau over a wide range of distances with virtually no gain in performance at close range.

    Lower velocity, larger calibre guns were the way to go when You intent to improve the power of the guns in view of the self-imposed limitation by rejecting higher quality steels, more complicated decrementally hardening and AP-caps for AP projectiles.

    Post war, these projectiles were introduced.

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