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.  

Video: Can an IS-2 hit a target at long range?

The IS-2's can penetrate the Panther's armour at effectively any range, but can it hit? In my latest video, I take a look at the theoretical and practical precision of the IS-2's 122 mm D-25T gun to see if it could hit a Panther-sized target at long ranges.

Video: IS-2 vs Panther, Math and Reality

I've frequently seen the claim that the front of the Panther tank was nearly invulnerable to the IS-2's 122 mm D-25T gun if correctly angled. Indeed, penetration equations suggest that would be the case, but reality is a lot more complicated than that. In this video I go into detail about how line-of-sight armour thickness doesn't tell the whole story.

A Round Too Long

Attempts to create fixed ammunition for the 122 mm D-25 gun in 1944-45

It is no secret that the firepower of tanks in WW2 increased dramatically. Armies of the world began the war wither with 37-47 mm long barrelled guns or 75-94 mm short ones. Some tanks even had armament composed only of heavy machine guns or small autocannons. Firepower of heavy tanks increased the most noticeably, particularly in 1943. German heavy tanks settled on the 88 mm caliber, the Americans focused on 90 mm guns with ballistics of the M3 AA gun. The USSR also initially chose an AA gun, an 85 mm one. However, there was a huge leap forward in the summer of 1943. The design bureau of factory #9 under the direction of F.F. Petrov developed the 122 mm D-25 gun by combining the D-2 122 mm gun (its ballistics were very close to those of the A-19) and the cradle of the 85 mm D-5T-85 gun. After trials in the Object 240 experimental tank, it was accepted into service as the IS-2 (IS-122) on October 31st 1943.

Comparing Shells

 "Report of the GBTU Self Propelled Artillery Directorate on results of comparative penetration trials of American, German, and domestic AP shells
May 13th, 1945

Firing according to the attached velocities was done at the Main Artillery Proving Grounds of the GAU at NKB proving grounds at Sofrino

Results of firing the shells at armour plates at prescribed velocities (see table)

#1: 76 mm AP shells against 50 and 75 mm thick plates.

The experimental shell from 60Kh30 steel shows undoubtedly superior results compared to the stock shell or the American shell.

Health and Safety

 "#850232

March 26th, 1945

Tank units armed with heavy tanks report instances where the spent brass catcher is removed from the 122 mm D-25 gun because it stops the spent brass from extracting fully.

The incomplete extraction of the brass is intentional and aids in reducing the fumes in the fighting compartment, as a portion of the fumes exit out of the gun barrel before it is removed.

I ask you to instruct tank units to stop removing the brass catcher as its absence results in serious bruising of the loader.

Chief of the Tank Usage Directorate of the GBTU, Major General of the Tank Engineering Service, Pechenikin
Chief of the 1st Department of the Tank Usage Directorate of the GBTU, Engineer-Colonel Oleinikov"

CAMD RF F.38 Op.11362 D.116 L.19
Printed in Glavnoye Bronetankovoye Upravleniye Lyudi, Sobytiya, Fakty v dokumentakh, 1944-1945 p.449

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

King Tiger Battlefield Penetration Trials

Field penetration trials weren't an unusual phenomenon during WWII. Soldiers often wanted to look with their own eyes at what their own weapons can do against the enemy, plus the sight of blowing holes in enemy tanks is always good for morale. In this case, two rare beasts were captured for trials: a Tiger and a Tiger II. 

"1st Howitzer Artillery Brigade of the Reserve of the Supreme Command
November 9th, 1944
#01909

For your information, I direct to you the results of experimental firing on Tiger and Tiger B tanks.

Forward these results to battalion commanders, and the results on SU-152 shooting to all troops.

Attachment: the aforementioned on 4 pages.

Chief of Staff of the 1st Starokonstantinov Order of the Red Banner Order of Bogdan Khmelintskiy Howitzer Artillery Brigade, Major Vinogradov"

Diagram #1: upper front plate and illustration of the angle and thickness of the upper and lower front plates.

One Piece

 "To the People's Commissar of Ammunition of the USSR, comrade Vannikov
Chief of the Red Army GAU, comrade Yakovlev
Deputy Chief of Armoured and Motorized Vehicles of the Red Army, comrade Korobkov

In accordance with GOKO decree #6868s issued on February 4th, 1944, the People's Commissar of Tank Production instructed the Kirov factory to study the issue of single piece ammunition for the 122 mm D-25 gun.

Panther Penetration

"Maximum penetration at which the armour of the German Panther tank is destroyed

Composed according to experimental firing data.

System	Ammunition type	Maximum distance in meters at which penetration was achieved  during experimental firing						Effect
		Front armour			Side armour
		Upper sloped plate (90 mm)	Lower sloped plate (50-65 mm)	Gun mantlet (100 mm cast)	Turret side (45-50 mm)	Upper side (45-50 mm)	Lower side (45 mm)
45 mm gun mod. 1942	APT BR-240	-	-	-	400	300	400	Complete penetration of the turret and hull side armour.
	APIT BZR-240	-	-	-	400	300	400
	APCR BR-240P	-	-	-	400	300	400
57 mm gun mod. 1941	APT BR-271	-	-	-	1200	1200	1200
	APIT BZR-271	-	-	-	1000	1000	1000
	APT BR-271 SP	-	-	-	1200	1200	1200
	APCR BR-271P	-	-	-	1200	1200	1200
76 mm regimental gun mod. 1927	HEAT BP-354A	-	-	-	600	600	600	Complete penetration of the sloped turret armour.
76 mm regimental gun mod. 1943	HEAT BP-344A	-	-	-	600	600	600
76 mm ZIS-3 mod. 1942	APT BR-350	300	300	-	1200	1200	1200	Penetrates the turret and the side of the hull.
	APCR BR-350P	300	300	-	1200	1200	1200
	HEAT BP-350	300	300	-	1200	1200	1200
SU-76	APIT BZR-354	300	300	-	1200	1200	1200
	APCR BR-354P	300	300	-	1200	1200	1200
SU-85	APT BR-365	1000	1000	1000	1500	1500	1500	Complete penetration of various parts of the hull.
	APT BR-365 SP	1000	1000	1000	1500	1500	1500
122 mm gun mod. 1938	HEAT BP-463	800	800	800	1000	1000	1000	Penetrates armour and detonate the ammunition.
KV-122	APT	1200	1200	1200	1500	1500	1500	A shot to the front destroys the tank.
152 mm gun mod. 1937	AP BP-545	800 m and closer						The front armour is penetrated.

Confirmed: Authorized representative of the Operational Department of Artillery of the 1st Belorussian Front, Colonel Levit

Confirmed: Colonel Utin"

Heavy Tank Destroyer

The ISU-152 is the best known Soviet heavy SPG. This was the most numerous heavy SPG in history and its career lasted for many decades, overshadowing its "little sister", the ISU-122. The vehicles had the same chassis and differed only in the gun (or rather just the barrel) and ammunition racks. It was the ISU-122 and not the ISU-152 that was the main product of the Chelyabinsk Kirov Factory. This was because the vehicles with 122 mm guns were meant to be heavy tank destroyers. Tank regiments that fought in IS-2 tanks were even reformed as artillery regiments with ISU-122 tank destroyers.

Bullseye

Back when I was active in the World of Tanks community, the idea that the D-25T gun could hit the broad side of a barn seemed bizarre and impossible to many. Documents suggesting otherwise elicited heated discussion, with many suggesting that this is anything from an outlier to a fabrication. Fortunately, these trials were commonly performed as a part of standard QA testing, and many similar results are available.

Industrial Accident

"Unscheduled report of an extraordinary event

Unit: GBTU Scientific Research Proving Grounds

Region: MVO

Event: wound during trials

Time: 10:00 August 8th, 1944

Location: shooting range of the NIBT Proving Grounds, Kubinka station, Western Railroad

Victims:

Rank and position	Name	Year of birth	Nationality	Education	Social status	Party affiliation	Place of birth	Nature of wound
Sergeant Loader	Toldykin, Fedor Pavlovich	1924	Russian	7 grades	Kolkhoz farmer	VLKSM	Sorochkinsk, Chkalov oblast	Ragged forehead wound
Sr. Sergeant Gunner	Butorov, Ilya Innokentivich	1922	Russian	5 grades	Worker	VLKSM	Bysherovo, Buryat Autonomous Soviet Socialist Republic	Minor head bruise

Description of the event:

On August 8th, 1944, at 10:00 when testing the effect of the D-25 122 mm gun (#266-44) installed on an experimental ISU-122 #249 against armoured hulls, the gun fired unexpectedly when loaded during the fourth shot, as a result of which the recoil of the gun wounded the loader Sergeant Toldykin (ragged forehead wound) and gunner Senior Sergeant Butorov, who received a minor bruise on the forehead."

CAMD RF 81-12038-312 p.373