M10s beating Tiger I at 800 meters.

[Sgt Joch]

I ran a more controlled test, 4 M4A3(76)W early in separate lanes using 76 mm APC M62 ammo, each firing at one Panther. I recorded the hit locations for the first minute of play two separate times.

results:

200 meters:

-front turret: PP.....................................2

-front turret: armor spalling......................1

-weapon mount:.....................................1

-weapon:..............................................1

-upper front hull: (no damage)..................16

-lower front hull: FP...............................10

400 meters:

-weapon mount: FP.................................1

-weapon mount: PP.................................1

-upper front hull: (no damage)..................24

-lower front hull: FP.................................3

600 meters:

-weapon mount:.....................................1

-weapon:..............................................1

-rear top hull:........................................1

-upper front hull: (no damage).................18

-lower front hull: PP................................4

-lower front hull: FP................................4

PP = partial penetration

FP = full penetration

obviously a limited test which partly explains why the 600 meters test shows more damage then the 400 meters test. However, it does raise some interesting points.

The primary weak point is the lower front hull (the area between the tracks under the nose) at all ranges and secondarily the front turret/weapon mount at 200-400 meters. No M62 shell managed to penetrate the upper front hull even at 200 meters, whether this should be the case or not is up for debate.

Another point is the hit location, 80-90% of shells are hitting the hull, depending on range, only 10-20% are hitting the front turret/weapon mount.

The 4 lower front hull partial penetration results at 600 meters may indicate "shatter gap"?

[womble]

WRT hit location. I think it's been established that at the point blank ranges you're testing, the "centre of mass" aiming model of the engine results in more hull hits than the proportion of the presented cross section might suggest should be the case, because the gunner is aiming at the CoM, and with that gun, at that range, will hit it more often than not.

[JasonC]

Um, the main thing to notice in those tests is that not nearly enough of the hits are on the turret at all. 2 weapon mount and 2 weapon hits out of 58, at 400 meters or more? Our of 99 shots including the 200 meter range, 3 weapon, 3 weapon mount, and 3 front turret hits? That's just crazy.

http://www.flickriver.com/photos/chrisstreckfus/2450734848/

It is 20% of the frontal surface area, easy, and covers as much area (at least) as the lower front hull. (Track hits should also be happening - see photo).

What should be happening is 50-60% of the hits strike the glacis and bounce, 10% or so hit the tracks and maybe to immobilizing damage (break a front sprocket wheel) or occasionally glance, and the remaining 35% or so hit either the turret front or the lower hull plate and go in. At close range, that is, out to 400 meters or so. As the range grows beyond that, the turret front hits should start getting "shell broke up" results, and maybe at much longer range the lower hulls likewise.

Upshot, about a third of front hits should be effective at close range, and at medium range that should by half or so and keep falling, to disappear at 1 km or so.

In the real AARs, the turret hits are if anything more common than that. Though some of that is side engagements certainly. The typical TD vs Panther AAR at close range is a laconic "destroyed the German tank with 2 shots". Nothing about needing 11 hits to find the turret...

[womble]

Sounds like either players need to put their Panthers hull down more often, or the gunnery model needs to allow for point-blank range shots to be aimed at known weaker armour, if those RL results are to be replicated. I don't think having each point of the frontal aspect have an equal chance to be hit (atm, AIUI, it's a normal distribution around the aim point and at close range, 2 SD doesn't include many turret hits). "Close"/"point blank" range will obviously vary according to what weapon you're talking about.

[John Kettler]

Sgt Joch,

Good stuff, but what most intrigues me is rear top hull hit at 600 meters. This strikes me as more than a bit odd for a fairly flat shooting gun relatively close. Now, for an M4A1, that seems like it might be more reasonable, what with the relatively looping trajectory for the M61 fired from the relatively low velocity 75mm gun M3.

Regards,

John Kettler

[womble]

Sgt Joch,

Good stuff, but what most intrigues me is rear top hull hit at 600 meters. This strikes me as more than a bit odd for a fairly flat shooting gun relatively close. Now, for an M4A1, that seems like it might be more reasonable, what with the relatively looping trajectory for the M61 fired from the relatively low velocity 75mm gun M3.

Regards,

John Kettler

The Sherman's taller than the Panther. I guess that makes top hits more likely as the range decreases. Even the "relatively" loopy L40 isn't going to be dropping enough for an engine deck hit due to gravity to be anything other than a fluke.

[Vanir Ausf B]

No M62 shell managed to penetrate the upper front hull even at 200 meters, whether this should be the case or not is up for debate.

Not really. The Panther glacis (upper front hull in game terms) resists 76mm APCBC equivalent to 202mm at 0°. US 76mm M62a1 penetrates only 124mm at 100 meters so there is no chance of penetration other than a weak point hit on the machine gun port. These do happen but are very rare in my experience (less than 1%).

Another point is the hit location, 80-90% of shells are hitting the hull, depending on range, only 10-20% are hitting the front turret/weapon mount.

The center of mass aiming does become more pronounced as range decreases due to less dispersion. One of my tests in the Tiger mantlet thread linked to earlier shows this.

The 4 lower front hull partial penetration results at 600 meters may indicate "shatter gap"?

Hard to say for sure, but I suspect not. My testing shows shatter gap manifesting as an increase in spalling and non-damaging hits and a corresponding decrease in partial and full penetrations.

[Sgt Joch]

Not really. The Panther glacis (upper front hull in game terms) resists 76mm APCBC equivalent to 202mm at 0°. US 76mm M62a1 penetrates only 124mm at 100 meters so there is no chance of penetration other than a weak point hit on the machine gun port. These do happen but are very rare in my experience (less than 1%).

Rexford? well that is the traditional view, but as you dig into the subject matter, it is not so black and white.

The upper front hull of a Panther (Panther G early in my tests) has armour 80-85 mm thick at a 55 degree angle. In the Shoeburyness test, M62 rounds could penetrate a 100 mm plate/30 degree angle at 500 yds, but could only achieve partial penetration of a 120 mm plate/30 degree angle at 100 yds. This was a standard U.S. test plate at 240 BHN which is relatively soft, the Germans used harder armour. At the july Isigny test, it was found that M62 rounds will not penetrate the upper front hull at 200 yds. That would seem to settle the matter.

However, the july Isigny test also stated that the M62 round will penetrate the 100 mm thick gun mantlet at 200 yds which shows that the armour can be defeated at a steeper angle. Then there is the question of quality of German armour in 1944. The August Isigny tests found a wide variation in quality. 2 out of the 3 captured Panthers used in the test had plates which cracked and suffered catastrophic failure after "relatively few hits":

You also have other factors which can affect the angle at which the shell penetrates the armour. For example, the terrain on which tanks generally fought, fields and country roads were not exactly level, you could easily have gradients of up to 10 degrees on "flat" land. You also have factors like the external ballistics of shells or variation in velocity which can affect angle/penetration.

Then there is the possibility that the shell will be deflected when it impacts the armour causing it to come in at a steeper angle. This could be caused by the area around the MG port/track skirt or even by welds/imperfections in the plate.

So, taking all these factors into account, a M62 shell could theoretically penetrate the glacis at a 45 or 35 degree angle where it would be able to defeat a good quality 80 mm plate or even defeat a 80 mm poor quality plate at a normal 55 degree angle. You could easily justify a max. 5-10% partial/full penetration range at 200 yds if you push the enveloppe.

However BFC is taking the traditional approach. (evidence of a German bias? ).

[Vanir Ausf B]

However, the july Isigny test also stated that the M62 round will penetrate the 100 mm thick gun mantlet at 200 yds which shows that the armour can be defeated at a steeper angle.

The mantlet is rounded so the angle of impact varies considerably depending on the exact spot. A hit near the apex of the curve would have an angle of impact near 0.

Then there is the question of quality of German armour in 1944. The August Isigny tests found a wide variation in quality. 2 out of the 3 captured Panthers used in the test had plates which cracked and suffered catastrophic failure after "relatively few hits":

Ideally CM would model armor degradation from impacts but it does not. Statements by Charles suggest that armor quality is modeled as a straight percentage of impact resistance, which is also how BFC did it in the CMx1 games.

You also have other factors which can affect the angle at which the shell penetrates the armour. For example, the terrain on which tanks generally fought, fields and country roads were not exactly level, you could easily have gradients of up to 10 degrees on "flat" land. You also have factors like the external ballistics of shells or variation in velocity which can affect angle/penetration.

This goes without saying and my assumption was that you tested on level ground.

Then there is the possibility that the shell will be deflected when it impacts the armour causing it to come in at a steeper angle. This could be caused by the area around the MG port/track skirt or even by welds/imperfections in the plate.

The only weld seams would be around the edge of the plate where it connects to adjacent plates and probably around the edge of the machine gun port. I do think the number of weak point penetrations is too low given the size of the machine gun port but proving that could be difficult.

[c2yeung]

I waited for a Tiger to pass me and sneaked in right behind it and got off 2 shots at its rear at about 300 meters with no apparent effect. I watched with horror the Tiger 's slowly rotating backward toward me. I was hopeful that my next shot will at least unnerve the Tiger so I stayed put instead of retreating, big mistake of course. I never got that 3rd shot.

[Vanir Ausf B]

BTW, one other factor is the shot trap created by the round mantlet on Panther D and A models. I have unfortunately seen no evidence of this in my testing so far and I am well over 200 recorded hits on the front turret (I am testing on ausf A mid).

[Vanir Ausf B]

The Tiger has unusually thick rear armor. At 80mm it is only 20% less thick than the front armor.

[Baneman]

The Tiger has unusually thick rear armor. At 80mm it is only 20% less thick than the front armor.

Oddball was wrong ?!?! :eek:

[Vanir Ausf B]

I'm not sure. What did Oddball say?

[Andrew H.]

I'm not sure. What did Oddball say?

"Why don't you knock it off with them negative waves?"

Although he may have another quote in mind...

[ridethe415]

Although he may have another quote in mind...

"The only way I got to keep them Tigers busy is to LET THEM SHOOT HOLES IN ME! "

[Vanir Ausf B]

Panzer IV vs Tiger at 750m and 10° horizontal offset (control group)

Hits on driver plate: 106

No damage: 1 (1%)

Spalling: 24 (23%)

Partial Penetration: 72 (68%)

Penetration: 9 (8%)

Sherman76 vs Tiger at 500m and 10° horizontal offset

Hits on driver plate: 105

No damage: 6 (6%)

Spalling: 47 (45%)

Partial Penetration: 50 (48%)

Penetration: 2 (2%)

The proportion of full and partial penetrations for the Sherman is 50% of hits compared to 76% in the control group. I suspect this is our shatter gap found at last.

Panzer IV vs Tiger at 964m and 10° horizontal offset (control group)

Hits on driver plate: 113

No damage: 4 (4%)

Spalling: 46 (41%)

Partial Penetration: 62 (55%)

Penetration: 1 (1%)

Sherman76 vs Tiger at 800m and 10° horizontal offset

Hits on driver plate: 108

No damage: 20 (19%)

Spalling: 66 (61%)

Partial penetration: 18 (17%)

Penetration: 4 (4%)

This is the most dramatic difference I found in my testing. The Sherman76 only manage a full or partial penetration on 21% of hits compared to 56% of the Panzer IV control group.

M10 vs Tiger at 800m and 10° horizontal offset

Hits on driver plate: 45

No damage: 4 (9%)

Spalling: 31 (69%)

Partial penetration: 8 (18%)

Penetration: 2 (4%)

A quick and dirty test with M10s replacing Shermans to make sure the above results are not unique to the Sherman.

Panzer IV vs Panther A mid (hull down) at 750m (control group)

Mantlet Hits: 142

No damage: 86 (61%)

Spalling: 0

Partial Penetration: 33 (23%)

Penetration: 23 (16%)

Front turret hits: 106

No damage: 13 (12%)

Spalling: 44 (42%)

Partial penetration: 45 (42%)

Penetration: 4 (4%)

Sherman76 vs Panther A mid (hull down) at 500m

Mantlet hits: 187

No damage: 123 (66%)

Spalling: 0

Partial penetration: 37 (20%)

Penetration: 27 (14%)

Front turret hits: 109

No damage: 17 (16%)

Spalling: 53 (49%)

Partial Penetration: 35 (32%)

Penetration: 4 (4%)

Against the Panther mantlet the Sherman 76 achieves partial or full penetration on 34% of hits compared to 39% for the Panzer IV. That is a very small difference and may even be within the margin of error. If there is shatter gap in effect against the Panther mantlet at 500 meters it is a very minor effect.

Against the front turret armor the Sherman penetrates 36% of the time compared to 46% in the control group. This is a more significant difference and does suggest some shatter gap, albeit only very occasionally.

Conclusions

1) My initial statement that there is no shatter gap in CMx2 appears to have been incorrect. Probably. This conclusion rests on the validity of using the Panzer IV as a close approximation of the US 76mm. I can't think of any reason it wouldn't be but I may have overlooked something.

The shatter gap in the game is much more subdued than Rexford's book suggests. I don't have a strong opinion on this either way, although the almost complete lack of shatter gap against the Panther mantet at 500 meters is a little troubling given real world US test results that showed no penetrations of the mantlet at that range.

2) Hits on the Panther mantlet never produce spalling. Odd.

3) Although I was not testing for it specifically I couldn't help but notice that there was not one single ricochet off of the Panther shot trap down onto the hull. Not one. This was in 544 recorded hits. If you include "weapon" hits that I didn't record the total sample size was well over 600. This is an issue that has been around since the game came out and was supposedly fixed in the 1.11 patch:

Panther "shot trap" on the lower turret mantlet (potentially) deflects shots downward into the hull as expected.

Apparently not.

[Sgt Joch]

Found this quote at GS. Unfortunatly no direct link to original quote, but still interesting:

(5) The frontal slope is far too heavy for the 3-in to penetrate even at close range. Hits at 135 to 200 yards merely gouge out chuncks of metal and deflect upwards doing no damage. One hit on the .30 cal ball mount drove it completely back through the tank and fired the vehicle.

However,one penetration was obtained on the reverse or 'belly slope' in front of the Mk V at a range of approximately 150 yards. This may have been a chance penetration and should not be relied on as an aiming point.

Hoyt K. Lorance

Major, 899th T.D. Bn.,

Commanding

Seems to confirm the weakness of the front "Glacis" plate (upper front hull) around the MG bulge.

[Vanir Ausf B]

More precisely, it confirms the weakness of the machine gun ball mount which is inside the opening in the glacis plate. But that was never in question. It's more about how often it got hit and whether that is reflected in the game.

Hits on the opening itself would also constitute a weak point, particularly if the distance from impact to the edge were within the diameter of the shell.

[Sgt Joch]

More precisely, it confirms the weakness of the machine gun ball mount which is inside the opening in the glacis plate. But that was never in question. It's more about how often it got hit and whether that is reflected in the game.

Hits on the opening itself would also constitute a weak point, particularly if the distance from impact to the edge were within the diameter of the shell.

Not exactly, the entire MG bulge could deflect the shot if it hits on the edge and could cause the shot to strike the plate at a steeper angle where it could potentially penetrate the plate. Its not just a case of hitting the opening.

[Vanir Ausf B]

Not exactly, the entire MG bulge could deflect the shot if it hits on the edge and could cause the shot to strike the plate at a steeper angle where it could potentially penetrate the plate. Its not just a case of hitting the opening.

That's not how it works. If a hit on the "bulge" deflected off onto the glacis plate it would be much less likely to penetrate than a shot which hit the glacis plate directly. There are three reasons for this. One is that the deflection will reduce the velocity of the round. Second is that the force of the impact on the MG bulge would likely deform the projectile. Third is that a steeper angle of impact on the glacis plate would increase the plate's effective resistance.

However, the armor directly surrounding the machine gun port would have reduced resistance because of edge effects. When a projectile strikes armor it attempts to penetrate by pushing the resisting material out of the way as it moves through the armor. With an impact well away from any edges the armor's resistance is fairly uniform in all directions. But when a projectile strikes near an edge of the plate the resistance is reduced in the direction of the free edge because there is only air backing the armor in that direction so the material is more easily pushed in that direction. How much the effective armor resistance is reduce is basically a function of projectile size and distance from the edge (larger projectiles produce edge effects at greater distance from the edge). This is complicated by other factors. If the plate edge is bolted or welded to an adjoining plate then the edge effect is greatly reduced. In the case of ports, they resist better than edges along the outside of the plate (unless those outside edges are attached to adjoining plates). Smaller ports produce less edge effect than larger ports.

In any case, the projectile will tend to follow the path of least resistance though the armor. That means that when edge effect is in play the projectile will tend to deflect towards the free edge. On the Tiger I mantlet hits along the top edge would deflect outward away from the tank while hits along the bottom edge would deflect downward towards the top hull or maybe turret ring. Hits on machine gun ports will deflect inwards towards the ball mount.

[c3k]

Lack of spalling behind Panther mantlet, a conjecture:

The Panther mantlet has a LOT of metal behind it. There is all the turret structure, the gun mount, the gun, various other desiderata. All of this could prevent any spalling from having any internal effect. No internal effect, no game result. So, although a bit of metal may flake off the inner face of the mantled, it gets ignored.

Such is a thought. It has all the logical consistency and strength of a summer's eve musing.

Ken