Panther Shot Trap Still Not Trapping

[Redwolf]

You are right, Vanir.

Also, you said there was a top hull hit, so Steve is not.

[Vanir Ausf B]

Yeah, I can' make heads or tails of what Steve said. His talk of "hull blockage" suggests that they thought my test was done under different conditions than it actually was. The shot trap isn't even on the hull :confused:

I'm also puzzled by the claim that one ricochet penetration blows my whole theory out of the water, despite my statement that I had seen 2 of them in past testing. I never claimed that they are impossible, merely far too rare. It sounds like Charles won the lottery 33 seconds into his test and then declared problem solved based on an extremely small sample size.

I should have some time over the next few days to do one last (hopefully) test. I'll remove the, eh, "blockage" from the lower hull and see if that is magically protecting the turret. It's a pain to test like that since the center of mass aimpoint will move down onto the upper hull which makes turret hits much less frequent.

[poesel]

Hmm, maybe because Charles moved the Panther a bit forward for his test. Thus the Panther is a bit higher and maybe this shifts the target point for the Sherman so that a shot trap shot is more likely.

Just guessing.

[Fizou]

Comparing Vanirs test and pics with what Steve has written.. doesn’t make sense to me.

The hull down could potentially block the "shot trap area" if it was high enough.. the pics show thats no way close to being the case.

Might it be that the low velocity of the Sherman gun, at that distance will hit at an angle so that the shot trap won’t come into effect?

I’m in way over my head here but I’m very happy to see you do these tests Vanir and trying to make sure everything is they way they are supposed to be. Also thanks to Steve for listning in.

[warrenpeace]

I don't think Steve's explanation can be correct, but I wonder if there isn't another possibility. Since the tanks are 800 meters apart, the time of flight for the projectile is about 1.3 seconds which means the projectile will fall 8.3 meters. So the sherman gunner has to aim this far above the tank. Therefore at 400 meters from the target the projectile is at its apogee and will be falling. I one assumes a triangle the shot is coming down at a slight angle of 1.19 degrees from perpendicular. (However, the angle will be slightly larger because the triangle assumption assumes a constant speed of falling and in reality acceleration is increasing. I don't have the math skills to figure this out.) I wonder if that slight downward angle is sufficent to make the shot trap untenable. When Charles moves the tanks up, I wonder if the decrease in angle is sufficient to allow trapping.

[Vanir Ausf B]

Because the mantlet is uniformly rounded I think a steeper angle of decent would simply move the shot trap area upwards on the mantlet rather than eliminating it.

[Battlefront.com]

Just getting back to this.

Charles was incorrect about the berm having much of an effect. He's a busy man so be impressed he even bothered to look into it

Looking at it more closely he doesn't see a problem. At 800m the type of Sherman doing the shooting would only have a marginal chance of hitting the deck armor in a ricochet situation. More likely it would hit the glacis and there's little chance of it doing more than scraping paint at that angle. Plus, remember that the penetration properties change dramatically when a second surface is in play. Namely deformation of the penetrator itself. Though that would change quite significantly depending on all kinds of variables.

Bottom line is that Charles agrees with some of the other sources out there... the shot trap does exist, it does have the potential for getting a "Top Hull" hit, and that hit could result in a penetration. But only very rarely.

BTW, tests done on anything other than a current build might not reflect how the game works now. We make a lot of changes over time and often we don't bother documenting small ones.

Steve

[Yeknodathon]

I'm sure the bubbles in the brain jar just fizzle with activity on this one.

[Vanir Ausf B]

Looking at it more closely he doesn't see a problem. At 800m the type of Sherman doing the shooting would only have a marginal chance of hitting the deck armor in a ricochet situation. More likely it would hit the glacis and there's little chance of it doing more than scraping paint at that angle.

I don't see how this could possibly be true. Drawing a straight line from the midpoint or lower on the mantlet to the glacis plate shows the deck armor blocks LOS to everything except perhaps the machine gun bulge.

Plus, remember that the penetration properties change dramatically when a second surface is in play. Namely deformation of the penetrator itself. Though that would change quite significantly depending on all kinds of variables.

It is certainly true that not every ricochet onto the deck armor would penetrate. But that armor is only 16mm thick on the Panther D and A, so it wouldn't take much.

Bottom line is that Charles agrees with some of the other sources out there... the shot trap does exist, it does have the potential for getting a "Top Hull" hit, and that hit could result in a penetration. But only very rarely.

BTW, tests done on anything other than a current build might not reflect how the game works now. We make a lot of changes over time and often we don't bother documenting small ones.

It seems odd that what Charles considers to be the proper frequency is a couple of orders of magnitude lower than what he thought it was in the CMx1 games. But if that is his decision then I don't see any way to change his mind absent concrete evidence to the contrary, which probably doesn't exist. But if CMx2 has it about right then it would mean the mantlet chin on the later Panther models was an over-reaction to a problem that barely existed. I don't think that is very likely, but I can't prove it so I'm moving on

[Battlefront.com]

Remember that CMx1's ballistics were, though advanced at the time, still peppered with "dice rolls" compared to CMx2's system. That's because many of CMx1's properties were not directly simulated. Therefore, using CMx1 as a basis for comparison isn't necessarily a good tool.

And you are correct that it's pretty tough to change Charles' mind without some sort of tangible evidence. I should know

Steve

[JasonC]

Vanir - do you have a pixel count (or width and height same thing) for your red region on your pic? Might compare that to the visible area again in pixels. You can approximate the angled bits as triangles on the sides of the center rectangles.

The idea is that the ratio, red pixels to all pixels, is an approximate hit probability on the shot trap area. If anything it is a lower bound, because the true distribution of shots would be centrally weighted, and the red is more in the center region than the overall average (since the latter has lots of peripheral non-red etc).

Second, if anyone has a 3D wireframe of the Panther front, I can offer to throw Mathematica at it and try to get a more accurate figure, even accounting for things like a 1 degree angle of descent and a 3 inch projectile diameter, central weighting etc. The game clearly has the required 3D wireframe, I just don't know how to get it out.

[Vanir Ausf B]

Remember that CMx1's ballistics were, though advanced at the time, still peppered with "dice rolls" compared to CMx2's system. That's because many of CMx1's properties were not directly simulated. Therefore, using CMx1 as a basis for comparison isn't necessarily a good tool.

And you are correct that it's pretty tough to change Charles' mind without some sort of tangible evidence. I should know

The interesting thing about the Panther shot trap in CMx1 is that because it used a higher chance of "weak point penetrations" of the front turret to approximately simulate ricochet penetrations off the front turret onto the hull -- which were indeed basically just die rolls -- Charles had to pick a specific percentage chance of a ricochet penetration. According to testing I linked to earlier he chose somewhere around 10% of all hits on the front turret. Allowing for margin of error the real number may have been a little higher or lower, but it was much, much higher than in CMx2. Like orders of magnitude higher. It's probably obvious by now that I find the CMx1 number more credible

[Vanir Ausf B]

Vanir - do you have a pixel count (or width and height same thing) for your red region on your pic? Might compare that to the visible area again in pixels. You can approximate the angled bits as triangles on the sides of the center rectangles.

The idea is that the ratio, red pixels to all pixels, is an approximate hit probability on the shot trap area. If anything it is a lower bound, because the true distribution of shots would be centrally weighted, and the red is more in the center region than the overall average (since the latter has lots of peripheral non-red etc).

Second, if anyone has a 3D wireframe of the Panther front, I can offer to throw Mathematica at it and try to get a more accurate figure, even accounting for things like a 1 degree angle of descent and a 3 inch projectile diameter, central weighting etc. The game clearly has the required 3D wireframe, I just don't know how to get it out.

The total mantlet area in this 2D grid is 1311 squares (23x57). Of that 204 (4x51) are in what I would estimate to be the shot trap area. That is 15.5%.

[JasonC]

Very useful. I might put it as high as 20% of the mantlet (5x53), but the mantlet is a minor portion of the front aspect of the tank. That was the question - what total pixel area do you see for the whole visible Panther front?

[c3k]

And then, of the ones that hit square on to that restricted area, how many have the correct ballistics and physical properties to ricochet, let alone the residual energy and orientation to penetrate the roof armor?

[Vanir Ausf B]

That was the question - what total pixel area do you see for the whole visible Panther front?

Oh jeez, no way am I counting that many little squares

[Vanir Ausf B]

And then, of the ones that hit square on to that restricted area, how many have the correct ballistics and physical properties to ricochet, let alone the residual energy and orientation to penetrate the roof armor?

Unknown, at least by me and probably by anyone. I understand that is just another way of saying that whatever Charles guesses is going to be assumed correct because it can't be disproved. But I will re-iterate that the Panther D and A top hull armor was only 16mm thick. By way of reference, a .50 cal. machine gun will penetrate 19mm of RHA at 500 meters and 0°. So my guess is that a fairly large portion of rounds that ricocheted down onto the hull would do some damage, even if just spalling.

One curious fact is that in all my testing I have never seen an impact on the top hull that didn't penetrate. That means one of two things. Either ricochets down onto the top hull are extremely rare but almost always penetrate when they do happen, or they are far more common than indicated by the hit text because the hit text only displays penetrations. I am currently doing testing that should shed some light on this (yes, I said I was moving on but counting those squared got me thinking again...)

[c3k]

How much armor plate can that .50 penetrate when it is sideways? How much velocity does it lose during the ricochet?

You see my point.

FWIW would a closer hit by a 57mm at a 1m elevation increase the ricochet chances? (Change the geometry and velocity.)

[Vanir Ausf B]

How much armor plate can that .50 penetrate when it is sideways? How much velocity does it lose during the ricochet?

You see my point.

Of course. But you see my point that a full-sized AP round could loose the large majority of it's penetrating ability on the ricochet and still be a threat to the thin top armor.

FWIW would a closer hit by a 57mm at a 1m elevation increase the ricochet chances? (Change the geometry and velocity.)

Because the Panther mantlet is uniformly round I don't think an elevation change would alter the chance of ricochet much if at all, although it probably would affect the direction of ricochet. From what I can gather, AP rounds with a short cross section are more likely to ricochet than rounds with lengthy cross sections. So a 37mm round would be a poor ricochet candidate but a Soviet 122mm round would be a serious threat.

[JasonC]

Vanir - the reason we have multiplication is so we don't need to count lots of the same thing. Just 3 elements - the center rectangle without any taper, height and width. Then one triangle on each side - bottom width w, height h, top "width" zero, so halved. Close enough. If you want to get more accurate, can have two side vertical rectangles too. This should not be hard - if you just post the pixelated pic I'll do it...

[Vanir Ausf B]

Vanir - the reason we have multiplication is so we don't need to count lots of the same thing.

Ah, multiplication! I knew there was a word for how I counted the shot trap area on the mantlet.

The total mantlet area in this 2D grid is 1311 squares (23x57). Of that 204 (4x51) are in what I would estimate to be the shot trap area. That is 15.5%.

This should not be hard - if you just post the pixelated pic I'll do it...

The main reason I have little interest in it is that I am not concerned about hits to any area other than the mantlet. But if you want to have a go at it I'll post up a pic of the whole front area.

[Vanir Ausf B]

[Vanir Ausf B]

FWIW would a closer hit by a 57mm at a 1m elevation increase the ricochet chances? (Change the geometry and velocity.)

Judging from this comparison pic I don't think the 57mm would be any more likely to ricochet. It looks like it has about the same ratio of length to diameter as the 75mm M61, or maybe slightly longer.

The only difference that velocity would make that I can think of is that higher velocity rounds may be more likely to disintegrate or severely deform than lower velocity but I don't have any source for that other than common sense.

From left to right

1, 37mm AP M74 Projectile, M16 Case

2, 37mm HE M63 Projectile, M16 Case

3, 57mm AP M70 Projectile, M23 Case

4, 57mm APCBC M86 Projectile, M23 Case

5, 75mm APC M72 Projectile, M18 Case

6, 75mm HE M48 Projectile, M18 Case

7, 75mm APC-T/HE M61 Projectile, M18 Case

8, 76mm APC-T/HE M62 Projectile, M26 Case

9, 3in APC Projectile, 3inch MkII case

10, 3in APC-T/HE M62 Projectile, 3inch MkII case

11, 90mm APC M77 Projectile, M19 Case

[JasonC]

Vanir - thanks, all I needed.

I get an estimate of the shot trap as 2.24% of the frontal area of the whole target. It should be center weighted somewhat higher than that - if I weight the track areas at 1/2 I get 2.64%. That means the range is about 1 in 38 to 1 in 45 shots from the direct front aspect should be hitting the shot trap area. If one wanted to account for some fraction of the shots hitting that area not ricocheting in the most likely downward direction for whatever reason, I can see the shot trap hit chance dropping to 2%. But it should be on the order of 2 to 2.5%, not well under 1%. It is also about twice as likely as weak points of the glacis (MG ball area).

There are similar sized areas for the turret ring (turret front below the mantlet and above the hull glacis, but straight rather than ricochet hits on that plate). The overall weak point area on the whole front aspect is a full 6% of the exposed area, split about 2.5% shot trap, 2.5% turret ring, and 1-1.5%% MG ball. For some rounds all those might count as vulnerable areas, for others only the 2.5% shot trap region. But way above the under 1% being reported in game tests. (Another 1-1.5% are gun hits).

The lower hull is another full 17% of the exposed area with center weighting - 1/6 basically. The best protected glacis minus MG ball is 38% with only the tracks down weighted, call it 3/8 likely to no more than 1/2 on the high end, of all front aspect hits. The tracks and track covers are a full 30% of the exposed area without center-weighting, and 18% even with center weighting - 1/6 is a lower bound for hits on those.

[BletchleyGeek]

Okay, I went ahead and counted the number of cells for the Panther lower mantlet, and I get 60. Since the whole area is about 56x69 (I think I miscounted), that yields a probability of about 1.5% (or about 99:1 odds).

As Steve says, this Panther shot trap thing is very rare.

So rare that I wouldn't even factor it in my decision making, I wouldn't ever bet any money against those odds, and I'm not surprised that I have never seen it in my games.