Video: Comparing the D-25T and 8.8 cm KwK 43 L/71

The IS-2 and King Tiger were equipped with some of the most powerful tank guns used in the Second World War, but which one of them takes the top prize? I compare the penetration power of these two legendary weapons in my latest video.  

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.

Evolution and Revolution

March 29th, 1945, was an important date for Soviet tank building. The IS-3 tank, the result of a deep modernization of the IS-2 launched in April of 1944, was accepted into service on that day. The IS-3 had a complex fate. The army did not initially want to mass produce it, although the decision to do so later proved correct. The IS-3 was the last Soviet tank to be accepted into service during the Great Patriotic War. It did not reach the battlefield, but it worked flawlessly on the ideological front. The appearance of IS-3 tanks at the Victory Parade in Berlin was a true shock for the Western Allies, and this tank remained the gold standard for a modern fighting vehicle for seven years.

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.

Small Modernization of a Large Tank

Many tanks received significant upgrades after they first saw battle. Practice often trumps theory, especially during WWII where military vehicles quickly became obsolete. The IS-2 heavy tank was no exception. It was built with enough armour to protect it from the German Tiger tank, but it turned out that there were more dangerous opponents on the battlefield. As a result, a modernized IS-2 tank entered production in Chelyabinsk in late summer of 1944. It is sometimes called IS-2M or IS-2 model 1944, but neither designation was used in reality.

T-44 Under Fire

The T-44 proved a tough nut to crack. Neither the Soviet 85 mm gun nor the German 8.8 cm Pak 43 could penetrate the upper front plate even from 100 meters. The lower front plate could not be penetrated by the 85 mm gun either, but the 88 mm gun managed to break it off after several hits. Despite the welding giving out, the protection was much better than that of the T-34-85, comparable to the Panther.

"Firing trials against the armoured hull resulted the complete destruction of the following welding seams: 

• Upper front plate and left side
• Lower front plate and left side
• Idler carrier and sides
• Hull roof and left side

The welding seam between the hull roof and right side was destroyed by 80%.

The overall view of the hull from the front after trials is show in figure 21.

Photo 21. Overall view of the hull from the front after trials.

CAMD RF 38-11355-2909 p.31

KwK 43 and the Schmalturm

Fantasizing about what might have been if the war in Europe continued past May of 1945 is not just a widespread hobby, but a profitable business. One of the vehicles frequently depicted laying waste to hordes of Allied tanks is the Panzerkampfwagen Panther mit 8,8 cm L/71 KwK 43, combining the firepower of a heavy tank and the mobility of a slightly less heavy tank. Yuri Pasholok wrote previously about how the gun, while technically fiting in the Schmalturm turret, didn't make the crew's life particularly pleasant. Let's take a look at a blueprint.

E-50 and E-75: A Story of Failed Unification

Tanks that could have been built are often discussed within certain circles. Aside from the superheavy Maus and E-100, there are the light and medium E-10 and E-25 tank destroyers. Despite very incomplete data about these vehicles, the overall characteristics are known, including the armament.

Meanwhile, the core of "Panzerwaffe-46" was going to be composed of the medium E-50 tank and heavy E-75 tank, at least in the minds of fans of alternative history. The story with these tanks is a lot more complicated, since work stopped at an early stage, and a good half of the information available on these tanks is divination at best. Let's try to figure out what about the E-50 and E-75 is true and what is blatant misrepresentation.

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

Pak 43 Problems

"Experience with 88 mm Pak 43 anti-tank guns

Front line experience showed that towed 88 mm anti-tank guns are of limited usefulness in mobile warfare (counterattacks, mobile defense, and especially when covering retreats).

Causes:

• The 4.5 ton mass, 1.9 meter height, and completely unprotected prime movers limit its mobility on the battlefield.
• As a rule, there is not enough time to organize a proper firing position.
• The gun, due to its size, cannot be concealed from the enemy (especially from the air).
• Due to the difficulty of turning the gun, it is difficult to defend against infantry at close range.

Conclusions: The towed 88 mm gun is only useful in positional warfare. In mobile warfare, it can only be used in the main directions of defense, for example in important sectors, control over which is especially important.

The manual 18/9 "Instructions on using the 88 mm Pak" issued on June 27th, 1943 is being revised."

CAMD RF 500-12480-24

Common Questions: Separate Propellant

I've been asked many times: what's the deal with two piece ammunition? Isn't it faster to load a gun when you only have to lift one item, and not the shell and propellant separately?

In an abstract scenario, maybe, but real life has a number of caveats. One is that ammunition is very heavy, especially once tank guns evolved from tiny 37 mm pea shooters that could be loaded with one hand to massive cannons where two piece ammunition could be required. Since odds are that you don't have an unlimited supply of formidable musclemen in your army, you might need to reduce the amount of weight someone would have to carry all at once, by splitting the shell into two parts, for instance. Recall that a loader would often have to flip the shell around, and that rotating an item that is very long requires more energy than rotating two shorter items the same amount.

The other problem with big ammunition is that as the caliber grows, the length of the shell grows as well. Since tank interiors are very cramped, this causes problems. The British make a note of the extreme length of Tiger ammunition in their first impressions and then comment on the extensive problems encountered when trying to load the Tiger II, whose shell was even longer. Note that the loader in this case has issues with both the weight and the length of the round.

Soviet trials of one piece ammunition discover the same thing: a 122 mm shell is too long and heavy to be able to load conveniently, limits the vertical range of the gun, and does not actually increase the rate of fire.

When tanks started using automatic carousel loaders, the issue of loader fatigue disappeared, but there was still a benefit to using two-piece ammunition. With long one-piece ammunition, it has to be stored in either a bulky turret bulge or surround the fighting compartment like a ring, making it very difficult to reach the driver's position without exiting the tank. Two piece ammunition can be stored in a much more compact way, without either of these drawbacks.

As with many cases in engineering, there is no one answer that is automatically "better". It is important to think carefully about your constraints when making a decision.

Novelties on the Baltic Front

"New armament of the German army

Interrogations of prisoners and captured documents demonstrate that the enemy forces opposing the Front have new types of armament. For example:

1. New electrically fired 88 mm anti-tank gun used by anti-tank gun companies. The gun can penetrate a T-34 at 3000 meters.
2. There is a new subcaliber HEAT shell for the 75 mm AT gun. The 37 mm AT gun was removed from AT units and transferred to infantry units.
3. Prisoners and defectors say that the German army designed a new type of submachinegun with a side magazine, but the submachinegun was not issued yet.
4. Many soldiers state that the MG-42 is impractical as it needs too much ammunition and jams often. Soldiers prefer the MG-34.
5. The Tiger uses additional 3 mm spaced armour placed some distance in front of the main front armour. This additional armour is meant to reduce the effectiveness of AP shells and to detonate HEAT and HE shells before they hit the main armour.
6. The 75 mm gun in new assault guns is movable, which makes aiming easier compared to earlier assault guns with an immobile gun.
7. Fully rubber gas masks, introduced in 1943, were taken away from all soldiers on March 15th, 1944, and replaced with old masks made from rubberized fabric. Soldiers without filters marked "April 1943" had their filters replaced with a filter with these markings. New filters have a large opening in the bottom covered with a mesh instead of many small openings."

Via biserg.

Common Questions: KwK 43 vs D-25T Penetration

One of my earliest articles was an explanation of the difference in Soviet and German penetration standards. Now, just as then, accusations of propaganda are quickly encountered when this table pops up. After all, it's easy to Google "D-25T penetration" and "KwK 43 penetration" and compare the results. You will, of course, find a number of theoretical values derived through various methods, but tanks fight wars on the battlefield, not in Excel, so let's take a look at some practical results.

The first test that I have where the two guns compete is against the armour of the Tiger II (CAMD RF 38-11377-129). However, due to its brittle nature, it's hard to establish the clear winner here. Nevertheless, I will include this test for completeness' sake.

As you may recall from the relevant article, one 88 mm shell fired into the front of the turret at 400 meters (it took three shots to get a "fair" penetration, the others hit the edge of an existing opening) penetrated the front of the turret (180 mm) flew all the way through, and penetrated the rear (80 mm) through a weld seam. This must have been confusing for some people, as I've seen claims that the gun penetrated 260 mm and that Soviet penetration tables are a lie based on this fact, but as you can see, it didn't quite happen that way.

Now, the D-25T. Using the older pointed type AP shell at 2500 meters, it penetrates the front of the turret, making a colossal hole in the armour (700 mm by 220 mm) and, for good measure, the roof (460 mm by 300 mm). The shell does not make it through the back, but at six times the KwK 43's range, it's not the most scientific of comparisons. Let's try a target with sturdier steel, like an IS-3.

"Photo #11. Overall view of the 90 mm thick overtrack hull of the modernized IS tank after a hit from an 88 mm armour piercing shell at 400 meters. Three tracks have insignificant damage."

CAMD RF 38-11355-2805

At the same 400 meters, the side of an IS-3 is tougher than the front of a Tiger II, eh? Let's see how close the KwK 43 has to get before penetration.

CAMD RF 38-11355-2872

At 300 meters, the KwK 43 can finally penetrate the side of the tank, but it's a "limit of rear surface" penetration, a standard where the shell only has to cause damage the rear of the plate, and not actually make it all the way through. The D-25T can achieve the same from 1100 meters, or make it clean through the plate from 600 meters. You can read more about the tests here, but the D-25T consistently penetrates the prototype hulls from a longer range than the KwK 43.

Data about how the Object 701 #1 hull stood up to these guns is also available, albeit not as detailed.

Target	D-25 penetration limit	KwK 43 penetration limit
Lower hull side	4400 meters	3790 meters
Turret side	3400 meters	2600 meters

Data obtained from M. Kolomiets, Heavy Tank IS-4 (Moscow: Tactical Press, 2014), pp. 39, 76

Why does this happen? Aren't the numbers in the Soviet penetration table very close? They are, but ballistics is a more complicated science than this. Through a phenomenon called overmatch, a shell that is significantly thicker than the armour it strikes gets a bonus to penetration, while a shell with a small caliber compared to the armour it tries to penetrate will face a penalty. The D-25's 122 mm shell is almost 40% thicker than the KwK 43's 88 mm shell, which makes it rather more effective. This lesson was well learned by Soviet tank designers: according to NII-48 standards a post-war medium tank only needed to resist 88 mm shells, while a post-war heavy tank had to resist both 122 mm and 88 mm shells.

Tiger II Trials: Gunnery

The previous article covered the mobility aspect of the Soviet Tiger II trials, this one will cover how its gun and turret performed.

"Maneuverability of fire

Aiming the cannon and coaxial machinegun is done with the turning mechanism, elevation mechanism, and hydraulic turning mechanism which works only when the engine is running. The hydraulic mechanism has two gears and is controlled by a foot pedal.

The horizontal aiming speed of the gun depends on the rate at which the engine is running. Data on the aiming mechanisms is given in the following table.

Mechanism	Range (degrees)	Number of turns in range	Angle for one turn
Turning mechanism (manual)	360	673	30 minutes
Elevation mechanism	22	36	36 minutes

The hand crank and hydraulic rotation mechanism are independent. The effectiveness of the hydraulic turning mechanism is given as follows:

Gear	Engine RPM	Turret traverse	Time
1	500	360	1 min. 20 sec.
2	500	360	1 min. 15 sec.
1	1000	360	1 min. 26 sec.
2	1000	360	43 sec.
1	1500	360	54 sec.
2	1500	360	27 sec.
1	2000	360	40 sec.
2	2000	360	20 sec.

The effort required to elevate the gun when the tank is horizontal is as follows.

Gun position	Effort in kilograms
	Elevation	Depression
-5 degrees	6	1.5
0 degrees	7	1.2
+5 degrees	9	2
+10 degrees	8	1
+15 degrees	10	2

The effort needed to turn the turret with the tank flat on the ground is 2-3 kg.

Turret and gun looseness:

The looseness of the gun is 3 thousandths vertically. The looseness of the turret is 4 thousandths horizontally.

Gunnery trials

Muzzle velocity and maximum pressure:

The stock round from the 88 mm KwK 43 tank gun was used. The results attained were averages from armour piercing and high explosive rounds, six of each.

Type of shell	Number of shots	Muzzle velocity	Maximum pressure
Armour piercing	6	1018	3006
High explosive	6	759	-

Examination of precision and accuracy of the 88 mm KwK 43 gun in place:

To determine the accuracy and precision of the gun with armour piercing tracer shells, the gun was fired at vertical targets from a range of 1000-2000 meters. Aiming was done with the telescopic monocular sight with variable magnification. The visibility was good. The angle of the tank was 0 degrees. Time to fire was unlimited. Correction to aim was made after every shot.

Conditions	Range	# of shots	# of hits	100% radius	50% radius
1st group, 4x4 meter target	1000	10	10	48 cm	36 cm
2nd group, 4x4 meter target	1000	10	10	67 cm	43 cm
3rd group, 6x6 meter target	2000	10	10	93 cm	62 cm

Precision and accuracy of the 88 mm tank gun KwK 43 at ranges of 1000 and 2000 meters are good.

Determining rate of fire and accuracy when shooting in place:

The rate of fire of the gun was checked against one, two, three, and four targets with HE shells, in groups of 5 shots, with the following conditions:

• The shells are in the ready rack.
• The time is counted from the "load" command to the last shot.
• Change of range is performed when shifting fire.
• Correction of fire is performed after every shot.

The results were as follows:

Conditions and targets	Range to target	# of shots	# of hits	# of close misses (within 30 meters)	Time to fire (seconds)	Rate of fire (RPM)
Manual turning mechanism
PzIII	800	5	3	2	54	5.6
PzII	800	2	2	-	58	5.2
PzIII 15 degrees away	900	3	3	-
PzII	800	2	2	-	57	5.2
PzIII 15 degrees away	900	3	3	-
PzII	900	1	1	-	70	4.3
PzIII	800	2	2	-
T-40 35 degrees away	1400	2	2	-
Hydraulic turning mechanism
PzIII	800	5	4	1	53	5.6
PzII	800	2	2	-	52	5.7
PzIII 15 degrees away	900	2	2	-
PzII	500	1	1	-	59	5.4
PzIII	800	2	2	-
T-40 35 degrees away	1400	2	1	1
PzII	500	1	1	-	58	5.2
PzIV	650	1	1	-
PzIII	800	1	1	-
T-40 35 degrees away	1400	2	1	1

The maximum aimed rate of fire when firing in place at one target with the manual traverse is identical to the rate of fire when using the hydraulic traverse, 5.6 RPM. When firing at multiple targets in a 35 degree range, the rate of fire is 5 RPM with the manual traverse and 5.4 RPM with the hydraulic traverse. The accuracy of the gun when shooting in place is good.

Effectiveness of firing from the move

An AP-tracer shell was fired at a 4x6 meter target at a range of 900-1100 meters under off-road conditions while moving at 10-12 kph. There were three attempts at 4 shots each. The tank was aiming at 0 degrees, aiming was done through the optical sight at the 2.5x setting while using the hydraulic turning mechanism.

Results: 12 shots were made, one of which was to range in and 11 were counted. 8 shots hit, or 72%. Effectiveness of firing on the move was as follows, from the center of the target:

1. x: -185 y: -80
2. x: -170 y: -55
3. x: -150 y: -20
4. x: -145 y: -15
5. x: +125 y: -10
6. x: +150 y: +150
7. x: +155 y: +185
8. x: +205 y: +305

Horizontal aiming with the hydraulic traverse allows precise aiming at the target, and the semiautomatic braking elevation mechanism allows precise aiming vertically. These two factors increase effectiveness when firing on the move.

As the tank broke down, it was not possible to fully examine the semiautomatic braking elevation mechanism over a large amount of shots fired on the move.

...

Reliability of the gun and its mechanisms

During trials, 152 shots were fired, of which 60 were AP-T and 92 were HE-fragmentation grenades. The recoil length was normal and fell within the range of 510-525 mm.

After 58 shots, the semiautomatic guide failed. (See photo #11)

Photo #11. Destroyed semiautomatic guide.

After 90 shots, the roller arm failed. (See photo #12)

Photo #12. Destroyed roller arm.

After a new roller was installed, 62 shots were made, and the gun functioned normally."

CAMD RF 38-11355-2860