75-mm M3 v. Mk IV armor

[Buq-Buq]

JW:

 

A nice copy of that picture, along with the M72 AP/M61 APCBC discussion quoted above can be found here:

 

http://www.com-central.net/index.php?name=...pic&t=10834

 

 

 

 

 

 

Mark

[jwduquette1]

heh I guess I don't get out much. However I am perfectly willing to admit that I could be wrong about the dude 2nd from the right. He could be holding a Lucky Strike.

 

I have another photo floating around here of a tank crewmen in Italy holding 75mm M72. I can't seem to locate it at the moment. Perhaps some of the leftovers from N.Africa got drug over to Italy?

 

On the topic at hand, after looking over the numbers -- by that I mean studying M61 test data against German flame hardened and MQ plate -- as well as digging through various verbal accounts of 75mm vs. late war PzKw MkIVs -- that the front of a PzKw MkIV was not "immune" to 75mm M61 APC. I think the front of a late war PzKwIV was potentialy a tough prospect for M61 -- depending upon range and compounded attack angle -- but the front of the panzer could be (and was) defeated with the Sherman's 75mm gun (as well as the M24's 75mm gun). A small amount of digging by anyone interested in the subject should result in a similar conclusion. Which makes me wonder what sort of research the original Wikipedia author actually did on the subject. Probably got his information from another wikipedia article.

Edited June 7, 2009 by jwduquette1

[alejandro_]

I have been trying to track the decision that led to the upgrade of Panzer-IV armour to 80mm in the hull. Hitler ordered "frontal armor" to be increased to 80mm, but this was not done in the tower. What was the criterion to choose front hull?

 

- Larger size?

- Unbalance of tower?

- More possibility of hits based on studies?

 

Here are some excerpts of Spielberg book on the Panzer-IV

 

Generaloberst Heinz Guderian reported that twelve Panzer IV tanks with 80 mm front armor plate had been requested for the landing in Malta that was planned for March of 1942.

 

On May 24, 1942 Hitler ordered that all Panzer IV tanks with the 7.5 cm KwK 40 were to be fitted with the additional armor plate, provided that this did not cause essential delay in production. If subsequent experience with this additional armor plate should astonishsingly show bad characteristics, then the vehicles produced up to that point would still be usable.On June 29. 1942, Hitler decided that the added armor for the Panzer IV was to be used only to a limited extent. A monthly production of 16 units was planned.

 

Page 53

 

...

 

At the same time (October 14, 1942 -my comment-) Hitler stressed his standpoint that what with the growing strength of enemy tanks, at least a part of the Panzer IV production must continue to have a frontal armor of up to 80mm thick, this being of extraordinary value.

 

According to the troop reports on hand on November 8, 1942, the additional 30 mm thick armor plates on the Panzer IV had proved itself in many cases despite the resulting technical problems of driving them. Since the new British 6-pounder (57mm) antitank gun could still penetrate the front (50mm) of the Panzer-IV at a range of 1000 meters, it was ecided that 50% of Panzer IV production be fitted with the 30 mm thick additional armor plates.

 

Page 59

 

...

 

On January 5, 1943, Hitler decided, despite negative test reports, that the Panzer IV should soon be built with an angled bow plate 100mm thick. Until it was scheduled to enter production , all Panzer IV tanks were to be fitted with 80mm front armour. The 47 Panzer IV ready for delivery at Magdeburg should therefore be fitted with front armor inmediately, sine they were intended for special use.

 

Pag 61-62

 

Spielberg, Panzer IV and its variants, Schiffer Military History (1993)

[Marek Tucan]

AFAIK it was because of turret balance, plus probably suspension.

[alejandro_]

Double post.

Edited July 5, 2011 by alejandro_

[cbo]

AFAIK it was because of turret balance, plus probably suspension.

 

Spielbergers 1998 book on the Panzer IV quotes a number of documents on the issue of adding armour to the Panzer IV, including those mentioned in alejandros post. They do not specifically adress the issue of increasing the turret armour, however.

 

There were several projects for an improved turret for the Panzer IV:

 

- B.W. 40 Einheitsturm which was a turret for both the Panzer III and IV with hydraulic traverse. No mention of armour thickness though, and the turret was cancelled in the summer of 1942, as it was assumed that Panzer IV production would end during 1943.

 

- Improved Panzer IV with sloping armour 1942-43. While substantial changed to the hull are discussed, the only mention of changes to the turret involved a thicker roof. The project was dropped because the weight would tax the hull beyond the limit of its construction, would upset Panzer IV production and possibly interfer with production of armour plates for the Panther.

 

- Panzerkampfwagen III/IV: Another project aimed at merging the Panzer III and IV, including a hull with sloping armour and a new suspension. It says specifically, that the turret would remain the as the Panzer IV Ausf. J. in the summer of 1944 the project was cancelled, again under the assumption, that Panzer IV production would soon cease.

 

- Panzer IV modernized with 7,5cm KwK 42 L/70 in a Schmalturm. This project never evolved very far, but interestingly, armour thickness of the turret was to be between 30mm and 50mm, i.e. like the existing turret.

 

- Simplified turret. This was drawn up by Krupp in 1944 as a hexagonal turret with no vision- or pistol ports, two hatches in the roof and one on the left side. Apparently no commanders cupola either. What is interesting with this projects is that it is the only one which has thicke armour: 80mm on the front, 80mm mantlet, 42mm sides and 25mm roof. The commander was moved behind the gunner, leaving room to move the gun further back. This project was also cancelled as it was assumed that Panzer IV production would cease in 1944.

 

The indication seems to be, that the turret - like the hull, was not really upgradable beyond what was achieved with the Ausf. G. Like the hull, it would require a redesign amounting to making a new turret to improve its characteristics. So while all the projects was dropped and the end of Panzer IV production was anticipated, they started patching up the basic design or redirect production to more promising turretless vehicles.

The 80mm frontal armour was a patch and one that was only intended to last until a Panzer IV with sloping armour could be designed (as per the quotes in alejandros post above). That project came to naught and the patching up continued.

On that background, One could be tempted to view the increase of the front hull armour as the anamoly, rather than the lack of thicker armour on the turret.

[Marek Tucan]

- Panzer IV modernized with 7,5cm KwK 42 L/70 in a Schmalturm. This project never evolved very far, but interestingly, armour thickness of the turret was to be between 30mm and 50mm, i.e. like the existing turret.

 

- Simplified turret. This was drawn up by Krupp in 1944 as a hexagonal turret with no vision- or pistol ports, two hatches in the roof and one on the left side. Apparently no commanders cupola either. What is interesting with this projects is that it is the only one which has thicke armour: 80mm on the front, 80mm mantlet, 42mm sides and 25mm roof. The commander was moved behind the gunner, leaving room to move the gun further back. This project was also cancelled as it was assumed that Panzer IV production would cease in 1944.

 

The indication seems to be, that the turret - like the hull, was not really upgradable beyond what was achieved with the Ausf. G. Like the hull, it would require a redesign amounting to making a new turret to improve its characteristics. So while all the projects was dropped and the end of Panzer IV production was anticipated, they started patching up the basic design or redirect production to more promising turretless vehicles.

The 80mm frontal armour was a patch and one that was only intended to last until a Panzer IV with sloping armour could be designed (as per the quotes in alejandros post above). That project came to naught and the patching up continued.

On that background, One could be tempted to view the increase of the front hull armour as the anamoly, rather than the lack of thicker armour on the turret.

 

Interesting, esp. these last 2 things. I always thought the Pz IV schmalturm was envisioned as just slapping a Panther Schmalturm on older chassis as emergency measure. Thanks for posting.

[alejandro_]

Thanks for the summary cbo. In the link below it is possible to see diagrams with the projects you mentioned.

 

http://panzerivtheworkhorse.devhub.com/blog/581522-einheitsfahrgestell-standard-vehicle-chassis-iiiiv/

 

On that background, One could be tempted to view the increase of the front hull armour as the anamoly, rather than the lack of thicker armour on the turret.

I am also thinking about the effect of turret rotational speed and other factors if the armour in turret would have been increased... in any case the increase in armor was due to Hitler's orders. Its possible that without him, the evolution would have been different.

[Lampshade111]

What penetration numbers are correct for the US M61 APCBC? I've seen the following used on occasion. All at 0 degrees of angle against plain RHA.

 

- 91mm at 0 meters and 81-82mm at 500 meters.

- 90mm at 0 yards, 83mm at 400 yards, and 76mm at 1000 yards.

- 94mm at 500 yards and 85mm at 1000 yards.

 

Plus plenty of other figures.

[Mobius]

What penetration numbers are correct for the US M61 APCBC? I've seen the following used on occasion. All at 0 degrees of angle against plain RHA.

 

- 91mm at 0 meters and 81-82mm at 500 meters.

- 90mm at 0 yards, 83mm at 400 yards, and 76mm at 1000 yards.

Plus plenty of other figures.

Those are pretty much the same. The other I haven't seen. But they would have to be normalized as to the armor quality and penetration criteria.

[Lampshade111]

Is this 0 meters/yards business correct? How could one test that? Even if they did such information wouldn't be practical.

[DB]

I could imagine several ways to get the "0 meters" figures - you could extrapolate back from a graph with points at 250/500/1000/whatever, or you could fire a round "hot" from a proof barrel and measure penetration at the equivalent velocity for a "normal" round. It's also possible to fire a round at the shortest "safe" range and just call that muzzle penetration.

[Mobius]

I think in some tests they have the charge set to give a specific velocity at a range. Probably at a safe distance. So the penetration at any range can be found by firing at the same target setup.

[Mk 1]

I think in some tests they have the charge set to give a specific velocity at a range. Probably at a safe distance. So the penetration at any range can be found by firing at the same target setup.

I believe that approach was common for US Army Ordnance tests. US guns were capable of firing at much higher chamber pressures (and so, at higher velocities) than the standard ammo.* To test penetration at range, they would go to their velocity-over-range table, find the velocity they needed, and load up some ammo to give that velocity at their standard test range.

 

*US Army Ordnance had an unreasonably high barrel life requirement in their specs. So US ammo was loaded up to fire at lower chamber pressures. Higher velocities (and better penetration) could easily have been achieved if the barrel life requirement had been relaxed.

 

-Mark 1