CMRT penetrations on highly sloped armor

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There are some quirky shot placements and penetrations going on in the game. Some shots are hitting 'top rear hull' and such with little to no LOS to the areas hit. Also, hits at extremely low angles are penetrating.

An example is a panther that was hit and KO'd. I examined the 'hit decal' and saw it was on the RO hatch. I figured it to be a ricochet off the mantlet (possible) but there was no decal on the mantlet. Several viewings showed it was indeed a very low angle hit on the hatch. I checked the panther's terrain and it was at such a slight 'forward slope' that I figured it to be 10-15 degrees(max). The gun was even lower down 'the valley'. This odd event was made stranger since the hatch opened and the RO bailed out!

It seems the penetration modeling is not taking ricochet factoring into account. A major factor in creating ricochets is the angle (of course) and the relationship between the shape of the AP rounds nose and the 'landing' of the projectile on it's 'side' (along the highly sloped armor) and the lack of the nose of the AP projectile having the chance to 'dig in'. In other words, it slides. A rule of thumb for creating ricochets is 20 degrees or less of sloped armor induces ricochets. Sherman tankers knew this and some of the turret field expedient armor add-ons used this to effect.

I see a gawd-awful thread at BF discussing a similar problem with the Panzer IV hull being penetrated by AP in a similar manner. The usual types are trying to hammer square pegs in round holes using 'maths' to create the illusion of 'groginess'. Not one person has the sense to notice that there is very little photographic evidence of Panzer IV's being penetrated on this highly sloped area. Also, the US Army documentation of these German AFV being vulnerable to AP rounds from 37mm, 57mm, 75mm, etc., show that area under discussion as being non-vulnerable. There are even nice pictures there with shady areas to demonstrate this. I can dig this up.

I would certainly like Mobius to comment since he seems to be here enough. That is, if he is not afraid to show up on one of MD's notorious 'lists'...?
 

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I would certainly like Mobius to comment since he seems to be here enough. That is, if he is not afraid to show up on one of MD's notorious 'lists'...?
Actually, there is evidence of the high angle PZIV type transmission housing roof being penetrated. You've probably seen it. It is on a picture of a Panzerjager IV knocked out by a few US 3" hits on the front. I wondered how that happened. One reason I read was that the thin plate sort of folds down from pressure of the shell until it rips. There are also records of hits during WWI Jutland battle where shells hit turret roofs at high angles and penetrated the turret.
 
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Actually, there is evidence of the high angle PZIV type transmission housing roof being penetrated. You've probably seen it. It is on a picture of a Panzerjager IV knocked out by a few US 3" hits on the front. I wondered how that happened. One reason I read was that the thin plate sort of folds down from pressure of the shell until it rips. There are also records of hits during WWI Jutland battle where shells hit turret roofs at high angles and penetrated the turret.
Another shot...

http://upload.wikimedia.org/wikipedia/commons/5/58/Sd.Kfz._162-1_Jagdpanzer_IV-70(A)_in_the_Musée_des_Blindés,_France,_pic-3.JPG

It is a very strange penetration. It looks like a piece of the hatch is gone along with the armor. I suppose the Panzer IV frontal armor arrangement may have been different. That heavy armor looks like crap. The interlocked welded armor actually snapped.

I have never seen a pic like that from a Panzer IV. I have seen something like that from a ricochet on a Nashorn. The AP hit the gun and deflected down onto the armor making an odd sized hole.

View attachment 46342
 
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NUTTERNAME

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The hatch seems 'faked' or a replacement. The armored hinges do not match the other side either. In any case, a hole like that seems more consistent with a large artillery shell coming in at an angle. Most likely set on delay.
 

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According to guys from the Eastern block there was no official BR-350 round. The Russians just left the 'B' off one of many versions of the BR-350B rounds. They may have a point as the BR-350A weighed 6.3 kg (MV=662) and the BR-350B weighed 6.5kg (MV=655).
 

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According to guys from the Eastern block there was no official BR-350 round. The Russians just left the 'B' off one of many versions of the BR-350B rounds. They may have a point as the BR-350A weighed 6.3 kg (MV=662) and the BR-350B weighed 6.5kg (MV=655).
For the CMRT period, I doubt any BR-350A rounds were still in use. But, yes, there is some confusion as far as markings, nomenclature, etc.

In any case, the BR-350A would be laughably worse in the situation depicted. In the case of the BR-350B, the projectile has no cap (it is a APHEBC not APHECBC) and is landing on it's ogive area. In other words, the flat nosed portion, which is meant to help dig in, is hardly engaging the target plate. What little edge of the flat front part of the BR-350B that does meet armor, is presented with extreme forces since the ogive is acting against it's ability to enter the armor. The edge area of the front of the penetrator would 'ride' the armor at best and the resulting forces would bring the back end of the mass of the projectile out of line with the original line of flight.

The whole 'T/D' argument is a non-player in this scenario is not allowing the 'D' to get into the 'T'. The ogive and extreme angle have effectively reduced the 'diameter' considerably. The lack of a cap (not the ballistic cap) forces the edge area to strike on it's own and shatter is certainly another possibility.

A APCR round would have similar difficulties since it's lightweight carrier would, likewise, strike the extremely angled armor first. It is well known that APCR has problems against sloped armor.

There may be edge areas, such as the hatches and possibly the interface with the vertical armor, but I really doubt that this armored area could possibly be as low a protection as some of the 'grogs' at BF are flapping about.
 

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The whole 'T/D' argument is a non-player in this scenario is not allowing the 'D' to get into the 'T'. The ogive and extreme angle have effectively reduced the 'diameter' considerably. The lack of a cap (not the ballistic cap) forces the edge area to strike on it's own and shatter is certainly another possibility.
From
http://www.dtic.mil/dtic/tr/fulltext/u2/a443218.pdf
It has been inferred that the function of the circumferential grooves in Soviet Soviet shot is to locate the region of subsequent fracture of the shot during the penetration of armor. It has been determined that highly sloped armor targets may be more effectively defeated by shot whose noses undergo fracture, permitting the blunt body section which remains to punch through the armor.
Under this condition of attack, (highly sloped armor) shot whose noses remain intact tend to ricochet off the armor. Thus the notching of ogival shot promotes their fracture to form blunt nosed projectiles when attacking sloped armor targets.

Against normal and low obliquity targets, the bending moment may be insufficient to fracture the shot, and they will penetrate in an intact condition which promotes best shot efficiency against such targets.
 

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I have seen that. It does not include 76.2 mm. And as far as an 'inference', I would prefer testing over that. Also, they mention 60 degrees as being highly sloped? I am referring to a degree of slope greater than that. 72 degrees as far as the Panzer IV plate under question.

I suppose the Soviets had something to say about attacking German tanks (I believe you have seen this also)...

(4)

The following U.S. military intelligence report on Russian tank tactics against German panzers was originally published in Tactical and Technical Trends, No. 16, Jan. 14, 1943. Against the Mark IV, fire as follows:

(a) From the front--against the turret, under the tube of the gun, against the driver's port, and the machine-gun mounting;

(b) From the side--at the center of the hull at the engine compartment, and against the turret port.

(c) From behind--against the turret, and against the exhaust vent.

Remarks: It should be noted that in firing against the front of this tank, the armor of the turret is more vulnerable than the front plate of the turret gear box, and of the hull. In firing at the sides of the tank, the armor plate of the engine compartment and of the turret, is more vulnerable than the armor of the turret gear box.
If the highly sloped area was as vulnerable as some of the 'maths' at BF state, I think the Soviets might have noticed and mentioned it!
 
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mOBIUS

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Here is the 76mm.
http://www.dtic.mil/dtic/tr/fulltext/u2/014698.pdf

Since highly sloped armor is more effectively coped with by blunt nosed shot, the notches thus serve to convert the shot, by deliberately fracturing it, into a shot of more efficient design.
The presence of notches in blunt nosed shot is more difficult to explain since such shots are already properly designed to cope with high obliquity armor. They may serve, however, to localize fracture, when it does occur, to the solid portion of the shot nose and thus keep the explosive cavity intact to insure a high order detonation after perforation of the armor.
 

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Round designation as opposed to projectile designation. For F-34.
UBR-354B - BR-350B AP - 1.080kg - 655m/s
 

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Page 20 has 60 degrees armor.

There is that 1972 US graph of the 122mm BR471B. It goes to 70 degrees.
 
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NUTTERNAME

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Page 20 has 60 degrees armor.

There is that 1972 US graph of the 122mm BR471B. It goes to 70 degrees.
Yes, I meant 30 degrees from horizontal. Same as 60 degrees from vertical. Which means that the Panzer IV glacis 73 degrees from vertical (or 17 degrees from horizontal), is a much greater angle than 60 degrees.

That test is using homogeneous US armor. I believe the German armor on the Panzer IV glacis is not the same. US test armor was way too soft.

I would be interested in seeing the 1972 test but, again, are we comparing apples to apples? The main concern is Panzer IV (or Brumbar or Stug IV or even the JagdPanzer IV (A)) having a frontal armor prtection that BF guys are saying is 30 mm of effective protection? Specifically, being attacked by a 76.2 mm projectile.
 
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mOBIUS

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That test is using homogeneous US armor. I believe the German armor on the Panzer IV glacis is not the same. US test armor was way too soft.
A guy who researches that quite a bit is saying that the hardness doesn't matter as much at high angles.
http://www.ww2aircraft.net/forum/ww2-general/german-75mm-v-allied-75mm-37327-4.html
I'm not so convinced.
Those guys at BF are using Lorrin Birds formula for Russian APBC shot which he developed by scaling that graph. In fact that is who originally posted that 122mm graph.
The only other high angle data I have is from modern tests (Military Technology magazine) of long rod penetrators during the late 1990's. Blunt rods do indeed have an effective high slope penetration less than the cosine rule. But not that much less, like only 10-15 degrees.
 
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