100 mm D-10 vs 88 mm KwK 43

The Red Army took the threat of German anti-tank weapons very seriously, and the 88 mm Pak 43 remained a reference point for enemy anti-tank guns even after the war. In part, protection from this gun was listed as a requirement for post-war medium and heavy tanks. These requirements allowed me to compare the penetration of the German 88 mm Pak 43 and Soviet D-25T. Turns out, a similar analysis was done using the 100 mm D-10T gun.

This data shows PTP limit (the velocity at which the rear of the plate remains intact) curves of the 88 mm gun against medium hardness cast armour. It is visualized in two ways. The first has impact angle as the X axis and impact velocity as the Y axis. A curve is drawn for different armour thicknesses. The second graph shows the same data, but with the thickness as the X axis and curves drawn for each impact angle.

From these graphs, we see that the 88 mm Pak 43 is a powerful weapon indeed. At point blank range, it can penetrate 120 mm of armour sloped at 60 degrees (incidentally, the armour thickness proposed for modernized IS-2 tanks in 1944). The IS-4's armour protection (140 mm at 60 degrees frontally, 160 mm at 30 degrees on the sides) also offers good but not perfect protection against damage from the 88 mm Pak 43.

At 1000 meters and a velocity of about 900 m/s, the gun can still penetrate 100 mm at 60 degrees or 130 mm at 50 degrees. These look very similar to requirements for the T-54's armour, making it very clear what opponent this tank was designed to fight. 

This data shows the same thing but for the 100 mm blunt nosed AP shell. The penetration is considerably higher. Rather than 120 mm at 60 degrees, the gun penetrates a hair over 160. At 50 degrees, this shell penetrates 180 mm of armour compared to the 88's 150. Unfortunately the graph for the Pak 43 does not show penetration at 30 degrees at point blank range, but extrapolation shows that it penetrated less than 200 mm of armour while the D-10 would penetrate slightly more.

At 1000 meters and a velocity of about 800 m/s the gun penetrates 140 mm of armour at 60 degrees and almost 160 mm at 50 degrees, again keeping a slight edge on the 88. At 30 degrees the gun penetrates 180 mm of armour, making it capable of penetrating both the front turret or the front hull of a Tiger II at ranges where the Tiger II can penetrated it back.

And finally, the 100 mm sharp-tipped AP shell. This shell is not as good as the blunt-tipped AP (same thing is observed with the 122 mm D-25's ammunition as well). At point blank range the gun penetrates 130 mm of armour at 60 degrees, a hair more than the 88 mm Pak 43. At 1000 meters penetration drops to almost 120 mm at 60 degrees or 140 at 50 degrees, still keeping just ahead of the Pak 43. At 30 degrees the gun penetrates less than 180 mm of armour, making it a little riskier to fight a King Tiger head on. 

When it comes to the Panther, a more realistic opponent, the 100 mm gun can defeat it at a great range. The upper front plate (85 mm at 55 degrees) can be penetrated at a velocity of about 600 m/s with the sharp tipped shell (a range of over 3 kilometers) and at even greater ranges by the blunt tipped shell.

RGAE F.8734 Op.8 D.249 L.1-6 via Yevgeniy Narimanov and Artem Belyakov.

Start of the T-54

 "May 7th, 1945

I report that in mid-February of this year I ordered NKTP factory #75 to develop a mount for the 100 mm gun in the T-44 tank with a new 1700 mm wide turret ring. The design and working blueprints are complete.

On May 5th of this year I gave orders to produce experimental prototypes of the T-44 tank with a 100 mm gun. Trials of these tanks are scheduled for June 10th.

As for stowing 50 rounds of ammunition as requested in your letter, it is very difficult to achieve. 34-35 rounds is much more realistic. Additional orders were given to factory #75 to investigate the possibility of stowing 50 rounds.

I will inform you of the results of this work.

People's Commissar of Tank Production of the USSR, V. Malyshev"

CAMD RF F.38 Op.11355 D.3048 L.9
Printed in Glavnoye Bronetankovoye Upravleniye Lyudi, Sobytiya, Fakty v dokumentakh, 1944-1945 p.487

100 mm Guns

 "May 17th, 1945

I report to you on the work performed by the People's Commissariat and factories #92 and #9 on improving the firepower of T-34, T-44, and T-54 medium tanks.

Two types of 100 mm guns were produced for these tanks with turret rings widened to 1700 mm.

• 100 mm LB-1 gun produced at factory #92 (Gorkiy).
• 100 mm D-10T gun incorporating design elements of the D-10S SPG gun produced at factory #9 (Sverdlovsk)

Both guns were installed in turn into a T-34 tank with an expanded turret ring and tested at the Gorohovets proving grounds from April 6th to April 27th. Trials included firing 100 shots and 500 km of driving.

D-25 vs D-10

F.16 Op.2154 D.4"Top Secret
To the People's Commissar of Armament of the USSR, comrade D.F. Ustinov

On your orders, we report on the issue of replacing the D-25 gun in the IS tank with the D-10T.

• Due to the higher rate of fire of the D-10 compared to the D-25, chiefly due to the single piece ammunition, it is reasonable to make this change, but only if an armour piercing shell is developed equivalent in penetration to the D-25's shell.
• No such shell is being produced at this time.
• We consider it necessary to preserve the D-25 gun in the IS-2 heavy tank. The latest trials at the ANIOP show a rate of fire of 4-6 RPM, this is a good result.
• The factory is wrapping up preparations for D-10S production in August-September of 1944.
• All armament production can be moved to produce the D-10T instead of the D-25 in October-November.
• 150 D-10T guns can be produced in October, 250 in November.
• To achieve this, factory #9 requires 4 600x6000 roughing lathes and two #6 milling machines.
• Production of D-25S guns should then be transferred to factory #75 or #221 in October.

Signed:

Mirzakhanov

Gonor

Fratkin

Ryzhkov

Petrov

August 8th, 1944"

CAMD RF F.16 Op.2154 D.4

An Alternative Layout

SPG designs hit a dead end in many nations by the end of WWII. The concept of a heavier gun on the same chassis stopped working. Regular guns were getting so large that there were issues with the chassis. The results were essentially the same as just putting the gun in a tank with a rotating turret. This was especially true for medium SPGs. Germany, the USSR, and Great Britain eventually ended up with medium tanks that had the same gun as medium SPGs. Several nations (especially Germany and the USSR) ended up overloading the front suspension. This led to a search for new solutions. This led to the Uralmash-1, the most unusual Soviet late war SPG.

Optimal Modernization

GKO decree #3892ss "On organization of 85 mm SPGs on the T-34 chassis at the Uralmash factory" was signed on August 8th, 1943. The first 100 vehicles of this type were ready by early September. The SU-85 ended up being the most numerous Soviet SPG of the war. However, the question of its successor was already raised at the start of its production. The cause of this was information from the Kursk salient about new German Panther tanks and Ferdinand SPGs. A program to develop a gun more powerful than the D-5 was launched in September of 1943. The result was the SU-100, the best Soviet medium SPG of the war.

None More Frightening than the Cat

German industry created three armoured vehicles during WWII that had a significant effect on tank building worldwide. The appearance of the Tiger made Allied tanks obsolete. The few Ferdinand SPGs that were built introduced serious changes into the Soviet tank program. The third tank was the Panther, and its influence was comparable to that of the Tiger.

The tank was a quite unpleasant surprise for the Red Army and its allies when it made its debut at Kursk. Despite its deficiencies, the Panther is a good candidate for the best German tank of the war. The Panther was superior to the Tiger in terms of armament and frontal protection, and was made in significantly higher numbers. Many tank designers were looking at the Panther when they were making the next generation of medium and heavy tanks.

D-10 in the IS-2

"To the Commander of the Motorized and Mechanized Forces of the Red Army, Marshal of the Armoured Forces, comrade Ya.N. Fedorenko

Having examined the results of comparative trials of the 122 mm D-25 gun and 100 mm D-10 gun, the Red Army GAU concludes that:

1. The rate of fire of the D-10 gun is up to three times higher than that of the D-25 gun, which is a significant advantage of the D-10 gun.
   The 100 mm D-10 gun presently has an insufficiently robust armour piercing shell, which does not guarantee reliable penetration of the Panther's armour at a range of over 1200 meters.
   The decision to install the 100 mm D-10 gun on the IS tank should be delayed until the armour piercing shell and semi-automatic mechanism of the D-10 gun are perfected.
   Since the 100 mm D-10 gun and its ammunition in its existing form are already significantly more powerful than the 85 mm D-5 gun, it is necessary to rearm the SU-85 SPG with the 100 mm D-10 gun, for which a pilot batch of SPGs with the D-10 gun should be produced with corrections of drawbacks of the gun and SPG that were revealed during trials.
2. The 122 mm D-25 gun reliably penetrates the front armour of the Panther tank from a range of over 2000 meters.
   The armour piercing shell of this gun is sufficiently robust, and the HE grenade has a sufficient explosion and fragmentation effect.
   Until the ammunition and components of the D-10 gun are perfected, the 122 mm D-25 gun must remain as the main armament of the IS tank.

Conducting experiments with the creation of a 122 mm single piece round is reasonable, but you must consider that the use of a single piece round will require a change to the chamber, sunk part of the shell, and the casing.

The mass and dimensions of a unified 122 mm round will make the loader's job more difficult, which will definitely not increase the rate of fire of the D-25 to the level of the D-10.

Regardless of the result of comparative trials of the D-10 and D-25 guns, the installation of the S-34 gun in a tank and an SPG will continue. 

Commander of Artillery of the Red Army, Chief Marshal of Artillery, Voronov
Marshal of Artillery, Yakovlev
April 20th, 1944"

CAMD RF 38-11369-490 pp. 35-38

D-10 and IS-2

"To comrade L.P. Beria

On installing the 100 mm D-10 gun produced by NKV factory #9 into the IS tank instead of the D-25 122 mm gun made by the same factory

In March of this year, I reported to you that NKTP factory #100 jointly with NKV factory #9 produced an experimental prototype of the IS heavy tank with a D-10 gun designed by factory #9.

Trials of the IS with a 100 mm gun showed that the 100 mm D-10 gun has undeniable advantages over the 122 mm D-25 gun as armament of the IS tank. These advantages are as follows:

Mousetrap

The Maus tank that was recovered by Soviet specialists did not sit idle in the Soviet Union. It was picked apart and its components were sent out for study. The armour composition and hull design were carefully studied. It would be a shame to demolish such a rare exhibit, so only the D-25 was allowed to fire on it, with the performance of other tank guns (the Maus' own 128 mm and the Soviet D-10) being only calculated.

Soviets vs M48 Patton

Fig. 2 Tactical diagram of complete penetration and satisfactory penetration limits when firing at an M48 tank with domestic 85 mm sharp tipped capped armour piercing shells.

Muzzle velocities higher than stock were tested at 100 meters with an increased charge.

1. Complete penetration limit of the lower front hull.
2. Rear plate integrity limit of the lower front hull.
3. Complete penetration limit of the upper side of the hull.
4. Rear plate integrity limit of the upper side of the hull.
5. Complete penetration limit of the lower side of the hull.
6. Rear plate integrity limit of the lower side of the hull.

100 mm Tank Gun, First Attempt

"To the director of the Kirov factory, Leningrad, in response to letter #838s sent on January 31st, 1941

CC: GAU UVNA Military Representative at the Kirov factory

NKTM Military Department Chief

March 13th, 1941

Having examined these projects developed at the Kirov factory under its own initiative:

• 412-1V, 100 mm tank gun, and
• 412-2V, 107 mm tank gun

the GAU UVNA has come to the conclusion that:

1. Both guns are equivalent and modern, both in their ballistics and armour penetration.
2. Out of the two presented variants, the 412-1V is not recommended for production, because:

Under Pressure, Part 2

In Part 1, we saw what happens to a tank crew when it's hit with a HEAT shell, whether that shell penetrates or not. However, getting hit with a kinetic penetrator has consequences too! Let's take a look.

"To compare, a table of measurements inside armoured compartments on impact from armour piercing and high explosive 76, 85, 100, and 122 mm shells with sensors positioned 200-1000 mm from armour, under the condition that the armour integrity was not compromised."

D-10 CIA Intel

The following are penetration and ballistics tables for the D-10 gun mounted in a T-54 tank recovered by the CIA from a Soviet manual. 

Comparative Penetration

"Conclusions

1. As a result of trials of D-25 (122 mm) and D-10 (100 mm) tank guns, the following penetration ranges against the upper front plate of the Panther tank were established:

Gun	Shell	Distance of complete penetration
122 mm D-25	Armour piercing	2000
100 mm D-10	Armour piercing	1200
German 88 mm gun (Ferdinand SPG)	Armour piercing	600
German 75 mm gun (Panther tank)	Armour piercing	No penetration

New Shells

"State Committee of Defense Decree #6434s
August 21st, 1944
Moscow, Kremlin

The People's Commissar of Armament (comrade Vannikov) must:

1. Produce a trial batch of 10,000 45 mm incendiary shells for the People's Commissar of the Navy according to NKV blueprints by November 1st, 1944.
2. Complete development of 100 mm incendiary and HE-I shells and perform trials before October 1st, 1944.
3. After satisfactory results with the 100 mm shells, develop 130 mm incendiary and HE-I shells by a deadline negotiated with the People's Commissar of the Navy.

Deputy Chair of the Committee of Defense, L. Beria"

RGASPI 644-2-377

Gun vs Tree

"To the Deputy People's Commissar of Armament, comrade Mirzakhanov
CC: factory #8 director, Major-General of the Artillery Engineering Service, comrade Fratkin

During trials of the SU-100 at Uralmash, two 100 mm 52-PS-412U guns mod. 1944 ##A1966 and 2506 were damaged by impact on tree trunks and require repair at the factory.

The elevation mechanism cover bolts of gun #A1966 were torn off, the turning mechanism was bent, and the elevation mechanism works unevenly.

The travel lock on gun #2506 was bent, and the elevation mechanism works unevenly.

The guns were removed and are now at the Uralmash factory.

I ask you to order the director of factory #8 to repair the guns, paid for by GBTU. Present the bill to the financial department of the Armoured and Motorized Forces, Moscow, Red Square #2, NKO building.

GBTU USA Chief, Major-General of the Tank Engineering Service, Alymov
Chief of the 2nd Department of the GBTU USA, Engineer-Colonel Kupriyanov"

CAMD RF 38-11369-53

T-44 Upgun

"To the Deputy Chair of the State Committee of Defense, comrade Beriya

[cut off] January 1945

The tank park of the German army consists 50% of heavy Tiger and Panther tanks. Our heavy IS tanks, ISU SPGs and SU-100 SPGs make up about 28% of our total amount of produced tanks and SPGs. The main tank of the Red Army is the T-34-85, which has difficulty fighting heavy tanks. The new T-44 medium tank produced at factory #75 in Kharkov has the same armament as the T-34-85 tank.

To improve the armament and achieve superiority in firepower for our tanks, I consider it necessary to install the 100 mm D-10T gun into this tank. It is very possible to install this gun.

Based on the above, I ask you to order the People's Commissar of Tank Production to produce an experimental prototype of a T-44 tank with a 100 mm D-10T gun to urgently begin mass production of the T-44 with this gun.

Marshal of the Armoured Forces, Fedorenko
Colonel-General of the Tank Forces, N. Biryukov

Penetration, Part 8: Cold War Edition

Time passes, friends become enemies, enemies become friends, but the need to know what your enemies are capable of doesn't go anywhere. Naturally, as the USSR continued its research into weapons, the United States continued trying to discover information on those weapons. This is what they came up with.

PAM 30-60-1 Vol. 3 Pt. 1 (composite image from several pages)

Lots of good old friends, as well as newcomers, so let's go through this list and see what we can find.

The first gun is the D-56T mounted on the PT-76 amphibious tank. It seems new and exciting, but it's actually just a boring old ZiS-3 in a tank form factor. So boring and old, in fact, that the penetration data comes straight from this table right here, for APHE at least. The APCR data is not recorded in that table (probably because it has less penetration than AP at this range). HEAT is also new, and clearly a different round than was tested with the F-34. That one didn't perform nearly as well.

The next gun is the S-53, mounted on the T-34-85 and T-44. The rate of fire of only 3-4 RPM is rather low (average sustained RPM using all racks according to Soviet data is 6). The penetration for APHE is the same as the Soviet table again, but APCR is new, same as with the D-56T. Unlike the D-56, however, this round is actually more effective than AP at this range, which is probably why it doesn't get HEAT.

Next is the D-10T, from the T-54. Unlike with the predecessor, the rate of fire is straight out of the manual. Here, the penetration for AP is much greater than the old Soviet table (likely owing to post-war ammunition). The HEAT shell for this gun packs quite a punch, way above the dinky old D-56.

Now here's the good stuff, the smoothbore U-5TS from the T-62. The tank was built around the gun, and it shows. New APDS ammunition puts the D-10T to shame, and HEAT penetrated an impressive 450 mm of armour. 

The D-25 is next, installed on every Soviet production heavy tank from the IS-2 to the T-10. Penetration here is a little higher than the Soviet table (160 vs. 147). Otherwise, there really isn't that many new things to be learned about it.

The successor of this gun, on the other hand, is much more interesting. This is the "122 mm T-10 tank gun", or better known to most as the M-62, mounted on the T-10M, but compatible with any D-25 mount. The AP shell of this gun penetrated 185 mm of armour at 1000 meters, which isn't that impressive. The bigger improvement is the HEAT shell, which penetrates a whopping 460 mm.

The next gun is a little more obscure, the 57 mm Ch-51M from the ASU-57 airborne SPG. The values here are lifted straight out of the manual (although APCR penetration at this range is listed as 101 mm in the manual instead of the 100 in the table). Looks like American intelligence was doing its job properly.

The next gun has a fancy title, but this is just the plain old ZiS-3 again. Comparing data with the D-56 will give you some differences in the mount, but otherwise, it's functionally identical.

The D-5S-85 is another gun you should be familiar with, from the Soviet SU-85 SPG. The same gun was mounted on the more modern ASU-85. As expected, its performance is exactly the same as the S-53.

The D-25S is another "double", with all data identical to its tank-based version, but in the end of the list, the ML-20 awaits! However, it doesn't have anything new to tell us. Penetration data is, once again, pulled straight from the Soviet table.

HE vs. Armour

I've briefly explored the effect of high explosive ammunition on armour (disappointing American HE and much more exciting Soviet HE of various calibers), but nothing exceptionally scientific. However, a paper by V.V. Gayun, A.V. Grishkun, O.P. Gusev, and A.V. Lisin titled Investigation of Damage Dealt by High Exposive Fragmentation Shells to Armour published in the Armoured Journal (Bronetankoviy Vestnik) gives some glimpse into how shells of various calibers act against armour. In the interest of brevity and not getting bogged down in scientific jargon, I will only translate a portion of the article and provide some figures.

Thankfully, there is plenty of practical data to go off here, and not just theory. The experiments involved 152 mm shells, whose devastating effects we have already seen, as well as Soviet 100 mm, 115 mm, 125 mm, and 130 mm shells. Of course, only knowing where you stand is of limited use if you cannot compare your progress with that of the potential enemy, so the British 120 mm gun with its HESH shells also makes and appearance. These shells are fired at armoured plates 2700 by 2500 by 170 mm, with sensors behind them to measure the impulse, which is judged by the scientists to be proportional to the damage caused inside the tank to its crew and equipment.

Since we've seen what a 152 mm HE shell can do, let's take a look at experimental data for this caliber first. Players of World of Tanks will be used to HE doing the same amount of damage to the tank no matter at what speed its hits, but in reality, this is not the case:

"An analysis of natural shots, static detonations, and calculations shows that the contribution of the explosive filler of a 100-152 mm HE shell contributes around 5-10% of the overall impulse (at an impact velocity of more than 700 m/s), and the main damage to the armour plate is dealt by the impact of fragments.
...
When increasing the impact velocity starting from 600 m/s, the impulse of a 152 mm HE shell grows considerably, and when decreasing it from 400 m/s to 250 m/s, it decreases by 2-4 times. When the impact velocity is 950 m/s, the impulse is 50 and 40 kNs for 0 degrees and 60 degrees respectively, which is 2-2.5 times greater than the 125 mm OF-19 shell.

At angles of impact close to zero, and the velocity of 250 m/s, the impulse of a 152 mm HE shell is less than that of a 100 mm HE shell with the velocity of 900 m/s. When the angle of the target is increased from 0 to 60 degrees, the impulse of shells hitting it at 850+ m/s decreases, but the impulse of shells hitting it at 250-700 m/s increases. Therefore, the 152 mm HE shell has a higher effect against armour than a 100-130 mm HE shell at impact velocities greater than 650 m/s and a comparable effect at lower velocities."

Fig 1. Experimental dependence of the impulse of 152 mm HE shells on the impact velocity (vc) at several angles of impact (α).

The ML-20. whose devastating effects on armour we've already seen. is not a very high velocity gun. Shells hitting the enemy would be flying at less than 600 m/s, giving us a pretty small range of impulse that causes such damage. How does this compare to other HE shells in the Soviet arsenal?

Fig. 2. Experimental dependence on impact angle α of the impulse from HE shells on an armoured plate.

1. 152 mm HE shell (vc = 950 m/s)

2. 130 mm HE shell (vc = 910 m/s)

3. 125 mm HE shell (vc = 780 m/s)

4. 115 mm HE shell (vc = 850 m/s)

5. 100 mm HE shell (vc = 790 m/s)

The 130 and 152 mm heavy artillery is the undisputed king here, but at very high velocities. Corps level artillery and tank guns would be unable to fire shells so fast. 100-125 mm tank guns (the D-10T and its post-war smoothbore cousins) seem like they woudn't do as much damage as we've seen the ML-20 dish out, but comparing the impulse values of these guns to the values in fig. 1 says otherwise. These guns achieve an impulse of about 20 kNs, same as the ML-20.

Now, let's see how these guns compare to British HESH. Unlike traditional HE, the explosive filler spreads itself around the plate it impacts to increase the effect. How much does this increase the effect? Here is the impulse achieved when hitting "a tank" (the specific type of tank is not mentioned).

Caliber, mm	Type	Impact velocity, m/s	Impulse, kNs
Turret
115	OF-18	680	8
125	OF-19	850	11
120	HESH	620	12.5
152	OF-29	800	15
Hull roof
115	OF-18	800	8
125	OF-19	850	9
152	OF-29	800	19
Upper front hull plate
115	OF-18	860	11
125	OF-19	850	14
120	HESH	620	12
152	OF-29	800	28

Turns out, not much better. 120 mm HESH is comparable to the slightly faster flying 125 mm HE, and it still greatly surpassed by 152 mm HE.