Cannot see where I was hit in tank?...

[Vanir Ausf B]

The barrel does not extend across the full width of the mantlet so that should not be necessary.

[JonS]

an excuse for why your test has failed to show a deflection off the mantlet down into the Panther. Here goes...

The Cromwell VII's 75L40 gun is poor bomb tosser. In order to reach 500m range, the trajectory of the shell must arc in. It is a minor arc, all things considered, but then the ability to hit the lower 1/3 of the Panther mantlet requires some very specific trajectories. The relatively low muzzle velocity of the weapon you've chosen may have something to do with it.

... except ... what the "thirds" exactly translate to on the mantlet will vary depending on the incoming trajectory, won't they?

Assume the Panther mantlet is a perfect half-circle. Looked at from the side, the 'top' third is from 10 o'clock to 12 o'clock. The middle third is from 8 o'clock to 10 o'clock, and the critical lower third is from 6 o'clock to 8 o'clock. But that's only for rounds that are coming in perfectly horizontally. If the round's trajectory is dropping as it comes in then 6 o'clock to 7 o'clock might be physically impossible to hit, given the geometry, and the critical lower third becomes 7 o'clock to 9 o'clock.

Won't it?

[Vanir Ausf B]

I would use a flatter-shooting gun such as the US 76mm, but generating large sample sizes with it are much more time consuming because it penetrates the Panther mantlet frequently at 500 meters, which is also of dubious historical accuracy (US test firing against Panthers showed the 76mm could only penetrate the mantlet out to 200 yards, and Zaloga states that the Panther was "essentially invulnerable" frontally to US 76mm APCBC).

EDITED to add: In the game US 76mm also penetrates the King Tiger Porsche front turret easily at 500m, so if you are playing a QB keep in mind that the KT's frontal armor in the game is essentially no better than a Panther.

[Vanir Ausf B]

I got one, although just one.

Cromwell VII 75mm vs Panther A @ 107m partial hull down behind 1 meter berm.

652 hits on the turret

469 -- 72% -- on the "weapon mount"

* 413 no damage

* 52 partial penetrations

* 4 full penetrations

* 0 spalls (?)

123 -- 19% -- on the front turret

* 55 no damage

* 49 spalls

* 19 partial penetrations

* 0 full penetrations

60 hits -- 9% -- on the weapon

Oddballs:

* 1 ricochet forward top hull penetration

* 1 forward top hull hit (no damage)

[c3k]

I would think that your penultimate oddball, "ricochet forward top hull penetration" is exactly what you were testing for. That could well be the dread (to the Panther) ricochet down from the mantlet through the hull top.

Now it's time to dig through references to see if the turret front/mantlet is resisting as it should...

Thanks,

Ken

[c3k]

Jentz, "Germany's Panther Tank", pp127-129, lists various penetration ranges.

NOTE: These are German penetration tables. The criteria for "penetration" was different for all the belligerants. The British, for example, only required half the shell to be "inside" the tank. The Germans, if I remember correctly, required a through and through hole, with the penetrator inside the tank in a condition to burst. (Meaning an APHE shell was intact.) Regardless of the specifics of my memory, the German criteria for calling it a "penetration" were more rigorous than that of any other belligerant.

These penetration data use the German penetration criteria AND assume that the Panther (being a target) is facing 30 degrees from the firer. This make the armor more resistant to penetration, obviously.

Cromwell 75mm M3 cannot penetrate ANY part of the Panther front at any range. (0m for Turret, Mantlet, Glacis, and Nose.) This is the same for Shermans and Churchills equipped with the same gun. (Ditto for the 6 pdr APCBC.)

The Sherman 76mm M1A1 penetrates...

Turret...700m

Mantlet...100m

Glacis...0m

Nose...0m

So...want to run some 30 degree offset tests?

[Amizaur]

Those tables were not determined by actual shooting tests, but simply calculated by people sitting far from the frontline, probably using intelligence data or even estimates of enemy weapons performance.

[womble]

The criteria for "penetration" was different for all the belligerants. The British, for example, only required half the shell to be "inside" the tank. The Germans, if I remember correctly, required a through and through hole, with the penetrator inside the tank in a condition to burst.

To me, that sounds like the difference between a CM "partial penetration" and a full one.

[c3k]

First, I must flog myself for my inability to spell "belligerent". There.

Second, I do not know what CM uses for penetration vs. non-penetration. Any attempt to correlate CM hit text with real world physics could be subject to correction.

Third, the WaPruef 6 penetration data was most definitely not pencil whipped.

I have hints and clues scattered amongst various texts, but it seems that they procured armor, set it up, then moderated the powder charge to simulate the velocity for various ranges. I.e., 1/3 charge for 2,000m test, which was actually fired on a range which was 500m long. (That previous was a total fabrication, only meant to illustrate a test technique.)

So, you are correct that they did not sit a Panther in a field and gradually move a gun in closer until it penetrated. (In point of fact, the shell had to penetrate 5 times at that range to count. (Smaller calibers needed more penetrations to count.)) What they did was take armor out of production and set it up. They did use enemy weapons when available. These tests were conducted in mid '44. They had plenty of 75mm M3 guns to test.

So... armor plate on a stand, guns with reduced charge to simulate longer range, armor at an angle... no, it's not the same thing as shooting at a tank. But, if AAR's are anything to go by, their test methodology produced results which corresponded exceedingly well with battlefield results.

Ken

[Amizaur]

I know that penetration tables for German guns (and probably for some captured enemy guns) were done this way.

But I doubt that the tables about "tank x penetrates tank y from such range" were done in such way. They were just calculated with some assumptions (like tanks are boxes done from homogeneous armor plate, no joints, no weak points, no variable plate quality, single plate thickness).

Take a look at some tables for other "tank vs tank" combinations. For example according to those tables, with 30deg side angle, the Panther can penetrate Sherman glacis up to 100m, and also can penetrate T-34 glacis up to 300m. The Tiger can penetrate T-34's front hull only from 100m (at 30deg side angle) - T-34 seem quite well protected against it - and Tiger can't penetrate Sherman glacis at all, at those (30deg) conditions - according to those tables.

Maybe those values were calculated assuming enemy tanks are made with good quality German armor plate.

The above even might be about to be true... in theory . Performace against a real T-34 tank would be most probably better, and against a Sherman too.

[Vanir Ausf B]

I would think that your penultimate oddball, "ricochet forward top hull penetration" is exactly what you were testing for. That could well be the dread (to the Panther) ricochet down from the mantlet through the hull top.

It is. The remaining question is whether a 1 in 652 chance of occurrence is accurate. I don't know, and I would be surprised if any historical data on that exists. But based on my results it seems the mantlet chin added to later Panthers was a waste of metal.

Cromwell 75mm M3 cannot penetrate ANY part of the Panther front at any range. (0m for Turret, Mantlet, Glacis, and Nose.) This is the same for Shermans and Churchills equipped with the same gun. (Ditto for the 6 pdr APCBC.)

The Sherman 76mm M1A1 penetrates...

Turret...700m

Mantlet...100m

Glacis...0m

Nose...0m

So...want to run some 30 degree offset tests?

Not really Rexford's book gives 75mm M72 solid shot AP (HE burster charge replaced with inert filler) penetration of 114mm vs RHA at 0m and 0° angle, so the results are reasonable given than I used Cromwells. US 75mm APCBC w/HE burster numbers vary. WO 291/741 says 101mm at 0m and 0°, while TM9-1907 says 90mm. Rexford chalks up the difference to ammo quality.

US 76mm is hard to pin down because you get into issues of shatter gap, which has a huge impact on what it can an cannot penetrate. My testing indicates CMBN does not model shatter gap at all, so 76mm penetration in game is best case scenario (frankly, this seems to be the case with all US and UK AP ballistic performance in-game, although notably UK 95mm HEAT performance has been dramatically decreased from CMx1).

[c3k]

The mantlet (as I'm sure you know) of the Panther should be 100mm. The turret front was also 100mm. That puts those penetration figures pretty close, but not enough overmatching, especially with the curvature.

(HE burster replaced with inert was a British decision, no? The US kept the HE charge in it, or that's what I always thought.)

I would be very surprised if CMBN ignores shatter gap since CMBO had it.

Your comment re: best case. Does that mean that you think 76mm is a bit too good?

Ken

[Vanir Ausf B]

(HE burster replaced with inert was a British decision, no? The US kept the HE charge in it, or that's what I always thought.)

Right. I should have been more explicit in my previous post.

I would be very surprised if CMBN ignores shatter gap since CMBO had it.

From World War II Ballistics: Armor and Gunnery Second Edition pg 33:

On 10° lateral impact hits on the Tiger E driver plate (100mm at 10° assumed vertical) effective armor resistance is 103mm at 0°. Above suggestions for shatter gap failure suggest 76mm APCBC hits would fail when penetration ranged from 109mm to 126mm, producing failures from 50m through 900m.

76mm APCBC hits on the 100mm cast Panther mantlet at 10° would be resisted by 98mm equivalent of rolled armor, and shatter failure would be expected when penetration equaled 98mm x 1.22, or 120mm. 76mm would penetrate at ranges below 300m, whereas U.S. tests resulted in 200 yard penetration ranges.

Since the above recommendations for shatter gap failure are based on average values, variations will occur and the methodology is less precise than other procedures in this booklet.

I can tell you from testing that in the game US 76mm has little trouble with the Tiger front hull, and can penetrate the Panther mantlet at 500m roughly half the time (I need to do some tests to nail down the actual frequency).

To be fair, tests in May 1944 at Shoeburyness, in England showed the 76mm M61 APCBC penetrating 100m RHA at 500m and 30° angle with no problem. The discrepancy could be due to uneven ammunition quality, which Rexford himself wrote about in this post made after his book was published. Apparently one of the three US manufacturers of 76mm APCBC used a manufacturing process that resulted in part of the shell being too soft.

Your comment re: best case. Does that mean that you think 76mm is a bit too good?

Not necessarily. Only that CM seems to consistently assume best quality ammunition. The same is true for 17 pdr APDS.