m4a3 sherman and some others

[Die Hard]

Maybe you should post some sources like I did so we can see how much of this is your opinion and whats based on sources.

I'm afraid not. I'm writing most from memory; I have to look up some numbers now and then, but that's all. I'm not going to look up everything and post book lists and pages; I simply can't be bothered to do that.

So, I'm afraid you'll just have to take everything I post at face value, which probably isn't much to you. Guess you'll just have to disregard my arguments like you have been up till now.

The Panzer 4 H was the only one with 80MM of frontal armor. The rest of the models had 50MM front plates.

The Ausf. H was the only Pz IV in service in 1944 until production switched to the Ausf. J in June 1944. The Ausf. H having been in production since August 1943. The earlier models had by then been converted to StuG IV's or JagdPanzer IV's, or other Pz IV based vehicles like ammo carriers and engineering vehicles.

Both the Ausf. H and J had 80 mm front armor, and the late-1942 Ausf. G's had their 50 mm armor augmented by adding a spaced 30 mm plate for a total of 80 mm front armor. The spaced 50+30 mm arrangement was in some ways superior to the later single 80 mm plate, though the 30 mm plate did not cover the driver's vision slit or the bow machinegun, so there were weak spots.

The turret armor was also easy to penetrate at only 50MM for the front and none of it has much slope to it.

What you need to understand is that the front armor of the turret of most tanks is shielded by the gun mantlet. The Pz IV Ausf. H's turret front had 50 mm of armor, but the gun mantlet acts as a shield increasing the effective front turret armor to 100 mm; a hit outside the mantlet would likely only result in a glancing hit or ineffectual penetration.

Hell that site Lusche posted has all the numbers for everyone to check and see. Even the Sherman 75mm gun could handle the Panzer 4 from under 1000 yards.

Not in 1943-1945. The maximum penetration of the 75 mm M3 on that page is 76 mm at 457 meters. That's not enough to ensure penetration of the Pz IV's 80 mm front plate or the turret's 100 mm, though it is close enough to make it possible under favorable conditions. Ironically the old 75 mm M3 was a better gun at close range than the 76 mm M1 that replaced it due to the unfortunate ammunition deficiencies of the M1.

Direct link to Tankers In Tunisia
http://www.lonesentry.com/manuals/tankers/index.html

Interesting read.

I'm sure it is. I'll have to read it later. Thanks for sharing.

[GtoRA2]

I'm afraid not. I'm writing most from memory; I have to look up some numbers now and then, but that's all. I'm not going to look up everything and post book lists and pages; I simply can't be bothered to do that.

So, I'm afraid you'll just have to take everything I post at face value, which probably isn't much to you. Guess you'll just have to disregard my arguments like you have been up till now.

Take your posts at face value?

No, since you can't come up with even a single source I will take your posts as I always have, with a HUGE grain of salt.

Without any kind of reference your just a poster with an opinion who refuses to back up his posts with any references. I would love to read a source on your claims about the tank ammo since not a single recent book I have read on the Sherman mentions anything like it. The only thing any of them talk about is the poor performance of the basic round APC round in the 76MM gun and those are the numbers I used.

So again I would love to read any sources you have on these ammo problems you mention.


Oh and on the mantlet acting as extra armor, ok sure, but have you take a close look at the Panzer 4? the mantlet does not take up the full turret face. On top of that, turrets rotate, so the sides take hits all the time.  30MM is not enough to stop even the 75 under 1000 yards.

Before you come back with the rounds were unreliable again, please back it up with something. Even if its a book I have to hunt down at a library.

[Die Hard]

Take your posts at face value?

No, since you can't come up with even a single source I will take your posts as I always have, with a HUGE grain of salt.

That will work too.

Without any kind of reference your just a poster with an opinion who refuses to back up his posts with any references. I would love to read a source on your claims about the tank ammo since not a single recent book I have read on the Sherman mentions anything like it. The only thing any of them talk about is the poor performance of the basic round APC round in the 76MM gun and those are the numbers I used.

So again I would love to read any sources you have on these ammo problems you mention.

Ok, but just because it is you!

You can read this very well done Tiger site, or pick up just about any half-decent WWII tank book dealing with the Western front.

http://www.fprado.com/armorsite/tiger1-02.htm


I'll even quote the relevant text... Just for you!

"Another fact that helped the Tigers a lot was the "shatter gap" effect which affectted allied ammunition, a most unusual situation where rounds with too high an impact velocity would sometimes fail even though their penetration capability was (theoretically) more than adequate. This phenomenon plagued the British 2 pounder in the desert, and would have decreased the effectiveness of U.S. 76mm and 3" guns against Tigers, Panthers and other vehicles with armor thickness above 70 mm. It should be noted that the problems with the 76 mm and 3" guns did not necessarily involve the weapons themselves: the noses of US armor-piercing ammunition of the time turned out to be excessively soft. When these projectiles impacted armor which matched or exceeded the projectile diameter at a certain spread of velocities, the projectile would shatter and fail.

Penetrations would occur below this velocity range, since the shell would not shatter, and strikes above this range would propel the shell through the armor whether it shattered or not. When striking a Tiger I driver's plate, for example, this "shatter gap" for a 76mm APCBC M62 shell would cause failures between 50 meters and 900 meters. These ammunition deficiencies proved that Ordnance tests claiming the 76 mm gun could penetrate a Tiger I's upper front hull to 2,000 yards (1,800 meters) were sadly incorrect."





For some light reading I reccomend By Tank into Normandy by Stuart Hills, who was a WWII M4 tanker, not just some historian. IIRC he mentions the shatter gap problem.

http://www.amazon.co.uk/Tank-Normandy-Cassell-Military-Paperbacks/dp/0304366404/ref=cm_cr_pr_product_top

Very good book.


If you want to get more technical on the guns check out the books by Ian Hogg.

http://www.amazon.com/exec/obidos/search-handle-url/ref=ntt_athr_dp_sr_1?_encoding=UTF8&search-type=ss&index=books&field-author=Ian%20Hogg

If you want a good introduction to the M4 in WWII check out M4 Sherman at War.

http://www.amazon.com/M4-Sherman-War-Michael-Green/dp/076032784X/ref=sr_1_2?ie=UTF8&s=books&qid=1242179452&sr=1-2

If you want to get really anal about the 76 mm M4 get M4 (76mm) Sherman Medium Tank 1943-65.

http://www.amazon.com/76mm-Sherman-Medium-1943-65-Vanguard/dp/1841765422/ref=sr_1_1?ie=UTF8&s=books&qid=1242179452&sr=1-1

It can get tedious in its detail at times, but still a very good read if you like the M4 (like I do).

Oh and on the mantlet acting as extra armor, ok sure, but have you take a close look at the Panzer 4? the mantlet does not take up the full turret face. On top of that, turrets rotate, so the sides take hits all the time.  30MM is not enough to stop even the 75 under 1000 yards.

The side and rear armor on the Pz IV couldn't stop much in the way of gun fire of caliber larger than 37 mm (and not even that in many cases), but that's true of most WWII tanks, especially those in the Pz IV weight range.

[E25280]

Not in 1943-1945. The maximum penetration of the 75 mm M3 on that page is 76 mm at 457 meters. That's not enough to ensure penetration of the Pz IV's 80 mm front plate or the turret's 100 mm, though it is close enough to make it possible under favorable conditions.

Except that it says that it is 76mm when striking the armor at 30 degrees.  Shouldn't one logically conclude that striking an 80 degree surface rather than a 30 degree surface should result in greater penetration?

What you need to understand is that the front armor of the turret of most tanks is shielded by the gun mantlet. The Pz IV Ausf. H's turret front had 50 mm of armor, but the gun mantlet acts as a shield increasing the effective front turret armor to 100 mm; a hit outside the mantlet would likely only result in a glancing hit or ineffectual penetration.

I tried searching a few images to see what a PzkwIV turret front looked like without the mantlet -- came up empty.  However, here are some pics that basically show what I believe to be true of the PzkwIV or any other tank mounting a relatively large caliber gun.  The first pic is of a chaffee tank, the others from a conversion of a churchill tank to convert it from sporting a 6lbr gun to a 75mm gun.  What I am pointing out is that the mantlet covers what is essentially a large gaping hole in the front of the turret.  Pay particular attention to the last pic, which shows just what is attached to the mantlet -- the gun, coaxal MG, sighting equipment and elevation gear.  A direct hit to the mantlet does not receive any benefit from additional armor - penetration of the mantlet would most likely mean damage to any of the mentioned equipment if not metal fragments bouncing around inside the turret harming the crew.




If you have pics of the PzkwIV's turret without the mantlet attached (that isn't one of the 75 pages of frigging plastic models I waded through to get these pictures   ) I would be very interested to see if they show the same thing.

As for a "glancing hit or ineffectual penetration" -- the actual mantlet on the PzkwIV sure looks A LOT smaller than the turret front to me . . . There is plenty of area for a hit to be both non-glancing and most likely very effective.

[GtoRA2]

Quote from: GtoRA2 on Today at 07:54:54 PM
“Take your posts at face value?

No, since you can't come up with even a single source I will take your posts as I always have, with a HUGE grain of salt. “

That will work too. 

See that’s the spirit, this shouldn’t be personal. I recognize you know a lot about Armor, I just do not agree with your conclusions. I have an open mind, if your right about the rounds breaking up I want to know about it.


Quote from: GtoRA2 on Today at 07:54:54 PM
“Without any kind of reference your just a poster with an opinion who refuses to back up his posts with any references. I would love to read a source on your claims about the tank ammo since not a single recent book I have read on the Sherman mentions anything like it. The only thing any of them talk about is the poor performance of the basic round APC round in the 76MM gun and those are the numbers I used.

So again I would love to read any sources you have on these ammo problems you mention.”

Ok, but just because it is you!

You can read this very well done Tiger site, or pick up just about any half-decent WWII tank book dealing with the Western front.

http://www.fprado.com/armorsite/tiger1-02.htm


You know that’s interesting, I have not seen that site on the Tiger, there is another a little like it that is insanely detailed on the Tiger 1. Like pictures of all the internal systems etc. Like a Jentz book online.
Here is the site I am talking about.
Tiger I information center

I really wish there were sites like this for US Armor.


“I'll even quote the relevant text... Just for you! 

"Another fact that helped the Tigers a lot was the "shatter gap" effect which affectted allied ammunition, a most unusual situation where rounds with too high an impact velocity would sometimes fail even though their penetration capability was (theoretically) more than adequate. This phenomenon plagued the British 2 pounder in the desert, and would have decreased the effectiveness of U.S. 76mm and 3" guns against Tigers, Panthers and other vehicles with armor thickness above 70 mm. It should be noted that the problems with the 76 mm and 3" guns did not necessarily involve the weapons themselves: the noses of US armor-piercing ammunition of the time turned out to be excessively soft. When these projectiles impacted armor which matched or exceeded the projectile diameter at a certain spread of velocities, the projectile would shatter and fail.

Penetrations would occur below this velocity range, since the shell would not shatter, and strikes above this range would propel the shell through the armor whether it shattered or not. When striking a Tiger I driver's plate, for example, this "shatter gap" for a 76mm APCBC M62 shell would cause failures between 50 meters and 900 meters. These ammunition deficiencies proved that Ordnance tests claiming the 76 mm gun could penetrate a Tiger I's upper front hull to 2,000 yards (1,800 meters) were sadly incorrect."

Now, this makes sense, and I have some of the books the site references so I will have to read through them again, but it seems to me like they are talking about the Tiger I and it does not apply nearly as well to the Panzer 4. 
The penetration information I linked is from the book you recommended below M4 (76MM) Sherman Medium Tank 1943-65 by Zaloga and I used the poorest performing AP round the 76MM shot, any of the other rounds would fair better. Not against the Tiger per say, but the Panzer 4, even with 80MM of frontal armor going to fair well at the ranges fought in Normandy and Northern Europe.  At least that’s my take based on the accounts I have read, and the books you reference below.




For some light reading I reccomend By Tank into Normandy by Stuart Hills, who was a WWII M4 tanker, not just some historian. IIRC he mentions the shatter gap problem.

http://www.amazon.co.uk/Tank-Normandy-Cassell-Military-Paperbacks/dp/0304366404/ref=cm_cr_pr_product_top

Very good book.


If you want to get more technical on the guns check out the books by Ian Hogg.

http://www.amazon.com/exec/obidos/search-handle-url/ref=ntt_athr_dp_sr_1?_encoding=UTF8&search-type=ss&index=books&field-author=Ian%20Hogg

If you want a good introduction to the M4 in WWII check out M4 Sherman at War.

http://www.amazon.com/M4-Sherman-War-Michael-Green/dp/076032784X/ref=sr_1_2?ie=UTF8&s=books&qid=1242179452&sr=1-2

If you want to get really anal about the 76 mm M4 get M4 (76mm) Sherman Medium Tank 1943-65.

http://www.amazon.com/76mm-Sherman-Medium-1943-65-Vanguard/dp/1841765422/ref=sr_1_1?ie=UTF8&s=books&qid=1242179452&sr=1-1

It can get tedious in its detail at times, but still a very good read if you like the M4 (like I do).

On your book links:

By Tank into Normandy by Stuart hills.
I have never heard of this one but I will buy it soon. I am on an armor kick so its all I have been reading about for months.

The ian Hogg one isn’t coming up on Amazon but I will poke around and figure that out.

The M4 Sherman at war by Green is great. Lots of good info, great pictures. Pretty good info. I don’t recall anything in here about the Panzer 4 being much of an issue but they agree with you more on the Panther. I will read through the 76 sections again. I had I though this morning but though it was pretty light, about 2 pages of info if that. Ill check again.  Really a great book though.

On the M4 (76MM) Sherman Medium Tank 1943 to 65 by Zaloga
Also a great little book. Covers the 76MM gun tanks, the small run o f 17Pounders the US Army was having made for them and later war variants. It does have a longer section on the 76MM gun and I will read through it again to see if I missed anything on the rounds breaking up against the Panzer 4. Tiger sure, I recall them talking about the shocking penetration issues with the new 76 and Ike being annoyed he was told it was more then enough to handle the Panther and Tiger. Good read.


Quote from: GtoRA2 on Today at 07:54:54 PM
Oh and on the mantlet acting as extra armor, ok sure, but have you take a close look at the Panzer 4? the mantlet does not take up the full turret face. On top of that, turrets rotate, so the sides take hits all the time.  30MM is not enough to stop even the 75 under 1000 yards.

The side and rear armor on the Pz IV couldn't stop much in the way of gun fire of caliber larger than 37 mm (and not even that in many cases), but that's true of most WWII tanks, especially those in the Pz IV weight range.

That is kind of my point, the Panzer 4 wasn’t anything special in its class. Nothing I have read, indicates US tankers thought much of the Panzer 4 or 3. The Tiger and Panther they rightfully feared.

Read that report I linked and note all the comments about the Pz 3 and 4 and how they would prefer the Sherman.

Hell the US Army thought the 75MM Sherman was up to the task of fighting the Panzer 4 before Normandy(well that’s not the whole story, they were still clinging to there silly tank destroy doctrine). It was the shocking loss rate and high number of Panthers that finally got them to push the 76MM Sherman’s into Europe. (That’s all from the Zolaga book you linked above)

Die hard, this was really fun, I like a good debate. It seems I have read much of the same material you have I just come to different conclusions. Granted I read some of it years ago, so I am going to go back and make sure I am not basing some of my opinions on wrong memories, but 2 of the books you linked, hang out in my bathroom and I re read sections all the time =D.

I would love to have another discussion on the Panther at some point. I think I could keep from going personal if you can.  Thanks for the post and the book links, it looks like I have some new library additions soon.

[GtoRA2]

Except that it says that it is 76mm when striking the armor at 30 degrees.  Shouldn't one logically conclude that striking an 80 degree surface rather than a 30 degree surface should result in greater penetration?
I tried searching a few images to see what a PzkwIV turret front looked like without the mantlet -- came up empty.  However, here are some pics that basically show what I believe to be true of the PzkwIV or any other tank mounting a relatively large caliber gun.  The first pic is of a chaffee tank, the others from a conversion of a churchill tank to convert it from sporting a 6lbr gun to a 75mm gun.  What I am pointing out is that the mantlet covers what is essentially a large gaping hole in the front of the turret.  Pay particular attention to the last pic, which shows just what is attached to the mantlet -- the gun, coaxal MG, sighting equipment and elevation gear.  A direct hit to the mantlet does not receive any benefit from additional armor - penetration of the mantlet would most likely mean damage to any of the mentioned equipment if not metal fragments bouncing around inside the turret harming the crew.

If you have pics of the PzkwIV's turret without the mantlet attached (that isn't one of the 75 pages of frigging plastic models I waded through to get these pictures   ) I would be very interested to see if they show the same thing.

As for a "glancing hit or ineffectual penetration" -- the actual mantlet on the PzkwIV sure looks A LOT smaller than the turret front to me . . . There is plenty of area for a hit to be both non-glancing and most likely very effective.

To help ilustrate that point.

Here is a photo of a very lucky shot on a Pershing in Europe. One of 2 or 3 lost I think. This one was fixed from what I read.

[Die Hard]

Except that it says that it is 76mm when striking the armor at 30 degrees.  Shouldn't one logically conclude that striking an 80 degree surface rather than a 30 degree surface should result in greater penetration?

Sure, which is why I said "it is close enough to make it possible under favorable conditions." Getting a dead-on shot on any armor surface is very "favorable".

I tried searching a few images to see what a PzkwIV turret front looked like without the mantlet -- came up empty.  However, here are some pics that basically show what I believe to be true of the PzkwIV or any other tank mounting a relatively large caliber gun.  The first pic is of a chaffee tank, the others from a conversion of a churchill tank to convert it from sporting a 6lbr gun to a 75mm gun.  What I am pointing out is that the mantlet covers what is essentially a large gaping hole in the front of the turret.  Pay particular attention to the last pic, which shows just what is attached to the mantlet -- the gun, coaxal MG, sighting equipment and elevation gear.  A direct hit to the mantlet does not receive any benefit from additional armor - penetration of the mantlet would most likely mean damage to any of the mentioned equipment if not metal fragments bouncing around inside the turret harming the crew.

First of all let's clarify the terminology: Ineffectual penetration does not mean that the tank or crew don't take damage, but that the tank remains in a fighting condition. The hit may damage equipment or wound crew, but will most likely not knock the tank out of the fight.

Secondly, there are several mantlet designs, some sporting a shield, some only protecting the gun port. The Germans favored adding shields to their mantlets, especially on their mid-late war designs.

Lets take a closer look at the Panther's mantlet (couldn't find a detailed Pz IV either):

Here you can see the mantlet... but it isn't the big rounded shield. The mantlet is the big square armor box with the visible machingun port.




Here's the shield lying by itself:





Ironically this picture of a destroyed Tiger is the best I could find to illustrate its huge shield that actually protects the entire front face of the turret:




And an interior shot just for good measure:




And here the large shield of a Pz III Ausf. L:







The interesting part about the Pz IV is that it originally didn't have a shield; it was added later to add protection:



As you can see the the early Ausf. A's only had a simple internal gun mantle, but later versions added a shield.

As for a "glancing hit or ineffectual penetration" -- the actual mantlet on the PzkwIV sure looks A LOT smaller than the turret front to me . . . There is plenty of area for a hit to be both non-glancing and most likely very effective.

Now this is a very useful picture:




The gun mantlet and shield covers about half to two thirds of the turret face. A lucky shot to the right of the mantlet could pass through the gunner's primary sight, and a penetrating shot lower and closer to the mantlet would kill the gunner. A penetrating shot to the left of the mantlet would most likely be ineffectual, but might wound the loader. A shot to the mantlet itself could indeed damage the gun, but it wouldn't kill the tank. However, disabling the gun would be a victory to the M4 as the Pz Iv's only option would then be to retreat.

However the picture illustrates really well how small a profile the turret has compared to the rest of the tank. Hitting that sweet spot in the gunner's face would have to be considered a lucky shot (although the gunner might disagree!).

[GtoRA2]

Now this is a very useful picture:

(Image removed from quote.)


The gun mantlet and shield covers about half to two thirds of the turret face. A lucky shot to the right of the mantlet could pass through the gunner's primary sight, and a penetrating shot lower and closer to the mantlet would kill the gunner. A penetrating shot to the left of the mantlet would most likely be ineffectual, but might wound the loader. A shot to the mantlet itself could indeed damage the gun, but it wouldn't kill the tank. However, disabling the gun would be a victory to the M4 as the Pz Iv's only option would then be to retreat.

However the picture illustrates really well how small a profile the turret has compared to the rest of the tank. Hitting that sweet spot in the gunner's face would have to be considered a lucky shot (although the gunner might disagree!).

I removed all the tiger stuff, since this thread is on the sherman, and we should stick to tanks in its class, and I think we can all agree a tank can be killed by a lucky hit through the site or coax ports on the turret or the direct view ports and a bow MG ports. The Turret weak spots re mane on some modern designs but all post war designs got rid of direct view ports and bow machine guns. It makes no sense to have a large hole in the front plate of your hull for an MG of dubious value.

I see a fair amount of 50mm armor on that turret face a 76MM Sherman would have no trouble hitting. Any frontal turret hit has a decent chance of hitting that thin armor.  Any hit on the turret under 1000 yards has a good chance of disabling or killing the tank. I would say that means it wont have much trouble with the Panzer 4.

Also what makes you think any penetration would only hurt the crew and not kill the tank? Any shot that gets inside could cause the tanks loss, you have no idea were the rest of that round is going to go inside, it could hit crew, ready ammo, electronics causing fires etc or be harmless. Plus crews have a tendency to panic and bail out when a crew member gets hit.

They are pretty comparable tanks really.

[Die Hard]

You know that’s interesting, I have not seen that site on the Tiger, there is another a little like it that is insanely detailed on the Tiger 1. Like pictures of all the internal systems etc. Like a Jentz book online.
Here is the site I am talking about.
Tiger I information center

I really wish there were sites like this for US Armor.

That's a great site! I use www.onwar.com a lot for looking up technical stuff quickly. Great site for what it is.

Now, this makes sense, and I have some of the books the site references so I will have to read through them again, but it seems to me like they are talking about the Tiger I and it does not apply nearly as well to the Panzer 4.

The shatter problem was observed with all armor that over matched the round. The 80 mm plate on the Pz IV did after all equal the Tigers side armor and the Panther's front armor in thickness (but not slope).

That is kind of my point, the Panzer 4 wasn’t anything special in its class. Nothing I have read, indicates US tankers thought much of the Panzer 4 or 3. The Tiger and Panther they rightfully feared.

The Pz IV was a good match for an M4(76); similar gun performance (disregarding the ammo deficiencies), similar weight (though the Pz IV was on the light side), similar mobility, similar protection (Pz IV had better hull protection, but the M4 had better turret armor). The M4 suffers a bit a longer ranges due to its size and that huge front plate that wasn't really thick enough. The Pz IV suffered from very poor side armor (however, in France the Pz IV had the advantage of ambush).

Now, the Tigers and Panthers got all the attention, but I would have a healthy respect for the Pz IV too, and I'm sure the allied tankers did too. In fact I would fear anything that had a long German 75 mm sticking out of it!

Die hard, this was really fun, I like a good debate. It seems I have read much of the same material you have I just come to different conclusions. Granted I read some of it years ago, so I am going to go back and make sure I am not basing some of my opinions on wrong memories, but 2 of the books you linked, hang out in my bathroom and I re read sections all the time =D.

I would love to have another discussion on the Panther at some point. I think I could keep from going personal if you can.  Thanks for the post and the book links, it looks like I have some new library additions soon.

Yeah, my book stash keeps growing steadily too. However I have to split my attention between tanks, aircraft and subs. Which topic I select for bed-time reading depends on my mood.

I'd love to discuss more armor with you at a later time but my bedtime grows near, and after this thread I think I will choose... subs.

Good night gentlemen.

[Ack-Ack]

and after this thread I think I will choose... subs.

Good night gentlemen.

Maybe we would get lucky and HiTech would post some pictures from his Dad's submarine career.

ack-ack

[stephen]

Another night watching multiple 88mm's bounce off Shermans turrets...

QUESTION... why didnt the allies supply tanks  built entirly from this Uber armor?

[BigPlay]

See Rules #2, #4 (enjoy the week off, you were warned)

[GtoRA2]

That's a great site! I use www.onwar.com a lot for looking up technical stuff quickly. Great site for what it is.

I have not seen Onwar.com before, interesting site. I like the timeline. More stuff to read. eheh

The shatter problem was observed with all armor that over matched the round. The 80 mm plate on the Pz IV did after all equal the Tigers side armor and the Panther's front armor in thickness (but not slope).

So now I am confused a bit. Is this a problem with Allied tank rounds or a problem for all guns and it was just worse for the allied stuff because the German armor was heavier?
So back to that text:
"Another fact that helped the Tigers a lot was the "shatter gap" effect which affectted allied ammunition, a most unusual situation where rounds with too high an impact velocity would sometimes fail even though their penetration capability was (theoretically) more than adequate. This phenomenon plagued the British 2 pounder in the desert, and would have decreased the effectiveness of U.S. 76mm and 3" guns against Tigers, Panthers and other vehicles with armor thickness above 70 mm. It should be noted that the problems with the 76 mm and 3" guns did not necessarily involve the weapons themselves: the noses of US armor-piercing ammunition of the time turned out to be excessively soft. When these projectiles impacted armor which matched or exceeded the projectile diameter at a certain spread of velocities, the projectile would shatter and fail.

Penetrations would occur below this velocity range, since the shell would not shatter, and strikes above this range would propel the shell through the armor whether it shattered or not. When striking a Tiger I driver's plate, for example, this "shatter gap" for a 76mm APCBC M62 shell would cause failures between 50 meters and 900 meters. These ammunition deficiencies proved that Ordnance tests claiming the 76 mm gun could penetrate a Tiger I's upper front hull to 2,000 yards (1,800 meters) were sadly incorrect."

So it says there is a chance? Did they do a study of any kind that shows percentages of failure? Did it only affect the M62 round? From the chards that Standard M79 AP will penetrate 92MM at 914 meters, was this round effected? They do not mention it.
I assume the M93 HVAP round was less affected by this?
Also would the Panther and Panzer 4 be effected by this as well when firing against the JS-2 100MM plates? If yes, the rate was less because the German ammo was better?

The Pz IV was a good match for an M4(76); similar gun performance (disregarding the ammo deficiencies), similar weight (though the Pz IV was on the light side), similar mobility, similar protection (Pz IV had better hull protection, but the M4 had better turret armor). The M4 suffers a bit a longer ranges due to its size and that huge front plate that wasn't really thick enough. The Pz IV suffered from very poor side armor (however, in France the Pz IV had the advantage of ambush).

Now, the Tigers and Panthers got all the attention, but I would have a healthy respect for the Pz IV too, and I'm sure the allied tankers did too. In fact I would fear anything that had a long German 75 mm sticking out of it!

I agree, on how close they are, they mainly why I said the later Shermans didn’t have any trouble with the Panzer 4. In my opinion, it would come down to the tactical situation and crew quality with a large advantage going to Germans for being on the defense.  I personally wouldn’t want to be in either though with the other shooting at it.

Yeah, my book stash keeps growing steadily too. However I have to split my attention between tanks, aircraft and subs. Which topic I select for bed-time reading depends on my mood.

I'd love to discuss more armor with you at a later time but my bedtime grows near, and after this thread I think I will choose... subs.
 

Oh the books I would buy if I won the lottery lol. Never have enough.
Good posts Diehard! Thanks for going to the trouble.

[Die Hard]

So now I am confused a bit. Is this a problem with Allied tank rounds or a problem for all guns and it was just worse for the allied stuff because the German armor was heavier?

It was an ammunition related problem. Many guns suffered from shells shattering; the British were plagued by this in Africa against German FH plate armor, and the Russians gave up on APCBC due to the shatter problem and mostly used APBC which is just a blunt-nosed solid shot with a ballistic cap. German gun effectiveness was due in large part to the superior performance of the ammunition, which is related to nose hardness. British tests against homogeneous armor resulted in:

102 mm penetration for German 75 mm APCBC at 2000 ft/sec impact velocity.
90 mm penetration for U.S. 76 mm APCBC at 2000 ft/sec impact velocity.
75 mm penetration for Russian 76 mm APBC at 2000 ft/sec impact velocity.

The shot shatter problem was also "stacked" in Germany's favor in 1943-1945 since German armor generally over matched allied AT rounds (armor thickness >= round diameter) and German AT guns generally over matched allied armor.

So it says there is a chance? Did they do a study of any kind that shows percentages of failure? Did it only affect the M62 round? From the chards that Standard M79 AP will penetrate 92MM at 914 meters, was this round effected? They do not mention it.
I assume the M93 HVAP round was less affected by this?

The author of that site is a bit vague on that. At or close to the end of the "shatter gap" (900-ish yards for the 76 mm APCBC vs. 80 mm plate) the rounds would sometimes fail, sometimes penetrate. As I mentioned earlier the US Navy tests against 3 inch (76.2 mm) armor found that the 76 mm APC/APCBC round failed 50% of the time at an impact velocity of 2,069 ft/sec, and 100% from 2,073 ft/sec to 2,376 ft/sec. So the "transitional" range where rounds would shatter only sometimes is very narrow and covers perhaps 50-100 yards. While other factors modify these numbers, generally speaking the "shatter gap" for the 76 mm M1 was 200-900 yards against an 80 mm plate, and 50-1,200 yards against a 100 mm plate.

The tungsten APCR/HVAP rounds were not affected by the "shatter gap" phenomenon, but all standard AP ammunition was (AP, APC, APCBC).

Also would the Panther and Panzer 4 be effected by this as well when firing against the JS-2 100MM plates? If yes, the rate was less because the German ammo was better?

I haven't heard/read anything about the Germans having shatter problems at all against Russian armor. There are many probable reasons for this, chief among them the high quality of German ammunition and the poor quality of Russian cast armor. To shatter an incoming shell the armor needs to have a very hard surface, and you only get that with high quality plate armor.

The following numbers are what I consider the relative armor strength in WWII. These are not "scientific" numbers, but they should be in the ball park:

German/Western Allies plate armor: 100% efficiency (i.e. the yardstick) and the only armor that regularly shattered soft-nosed AT shells.
(Late 1944-1945 German plate armor: 70-90% efficiency due to lack of good alloying metals.)

Western Allies cast armor: 80% efficiency.

Russian cast armor: 50-70% efficiency (quality varied a lot)

So when comparing armor thickness consider the quality of armor involved.

[Angus]

Lusche, thank you for the website link. This is excellent!
Now, I did claim that the 17 pounder could afford a shootout with the German guns, although the allied armour (notably the Firefly) could not allow any "exchange". Here is what the website gave me:
The 17 pounder with Apcbc ammo (muzzle velocity 884 m/s, projectile weight 7,71 kg)  could penetrate 140mm at 457 m range, 130 at 914m, 120 at 1371m, and 111 at 1828m.
With an apds round, you had a projectile up to 3.71 kg’s and a muzzle velocity of 1204 m/s. Penetration in the same ranges would be 208mm, 192mm, 176mm and 161.
The Tiger I’s main gun, 88mm KwK36, could fire shells in the range of 7.3 to 10.2 kilogrammes, and penetrate at best (APCR, 7,3 kgs, 930 m/s) 170 mm at 100 meters, 155 at 500, 138 at 1000, 122 at 1500 and 110 at 2000.
The Panther’s main gun, KwK 42 would fire it’s anti tank round (apcbc) of 4.75 kg at 1120 m/s and penetrate 194 mm at 100 meters, 174 at 500, 149 at 1000, 127 at 1500, and 106 at 2000.
All figures take aim of 30 degrees angle.

So, I didn't even bother to take the Panzer IV into the comparison, these are the vaunted Tiger and Panther tanks.
The 17 pdr is, thereby quite well in the club, wouldn't you say.
BTW, Tiger's thickest part is 110mm? And the strongest part of those two would be the front of the panther?