Yak-9T - incredible firepower (or maybe incredible tank's lack of armor?)

[JtD]

I hope that you are aware that by far the most WW2 AP rounds were explosive rounds. For a reason. For instance, rounds having pierced armour do not retain most of their energy, unless the armour wasn't worth mentioning in the first place. Rounds without explosives usually were some hard core rounds (tungsten for instance), which offered superior penetration at the expense of damage capacity. In case of aircraft guns this often was a popular trade off, since the small calibre guns otherwise wouldn't penetrate at all.

For comparison, the very good German 30mm tungsten core round carried only 75% the energy of the standard AP round, at the muzzle. Further away, even less. It had far better penetrating power, more than two times as much at 500m, but if both rounds got through, the standard round would wreck far more havoc.

[Pursuivant]

Originally Posted by JtD

I hope that you are aware that by far the most WW2 AP rounds were explosive rounds.

Actually, for much of the war, tanks mostly carried standard AP rounds. Ammo like HEAT/APEX or HESH were later war innovations and they were often in short supply, as were standard AP rounds with tungsten penetrators.

As I mentioned in my previous post, a simple AP round penetrating armor generates plenty of heat and shrapnel even without the benefit of an explosive charge. Obviously, APEX or its ilk are better, and tungsten core penetrates better, but ordinary AP is plenty deadly against armor.

Conversely, soft vehicles sometimes fared better when hit by AP rounds, since the round might penetrate without fragmenting (e.g., going through the wood and canvas sideboards of a truck) or produce minimal fragments (e.g., punching through the sheet metal of a car's body). Very soft targets, like canvas or flesh, might not even trigger HE rounds.

This also holds true for cannon shells against early war canvas-covered aircraft like the Hurricane. AP rounds would just punch a small hole in the canvas without weakening the plane's structure, and HE rounds might blow through without exploding.

[Igo kyu]

Originally Posted by JtD

I hope that you are aware that by far the most WW2 AP rounds were explosive rounds.

No offence intended, however:

In the context of tanks, I am not aware of that. Air to air AP may have been different, there wasn't that much armour in 'planes, and doing damage once the armour was pierced would probably be worth it.

For a reason. For instance, rounds having pierced armour do not retain most of their energy, unless the armour wasn't worth mentioning in the first place.

That is not what happened. If a shot hit some armour, then things happened very fast, microseconds not milliseconds. When there is an impact, the parts can rebound without damage, or one can be damaged, or very unusually, both. The reason it's unlikely that both will be significantly damaged is that it's more or less a race to be the last to pass the limit of elastic deformation. The item that reaches the limit of elastic deformation first, is deformed plastically, and damaged. The item that is damaged gives way to the item that is undamaged, and the energy that was stored in the elastic deformation of the surviving item is restored in the rebounding of that item to its normal shape (which is why it's silly for tanks to have hitpoints that can be whittled away in some other sorts of games, shot either pierces the armour, or does almost no damage).

For comparison, the very good German 30mm tungsten core round carried only 75% the energy of the standard AP round, at the muzzle. Further away, even less. It had far better penetrating power, more than two times as much at 500m, but if both rounds got through, the standard round would wreck far more havoc.

That's not what I understood of tungsten core rounds. They were compressed in the barrel to get a much higher muzzle velocity, and since KE= 1/2 MVsquared, though the mass might be less the higher energy made penetration much more likely. Sabot rounds were similar, apparently less accurate than normal AP rounds, but much higher velocity, and thus KE, and therefore more likely to penetrate if they did hit.

[Pursuivant]

Originally Posted by JtD

One can also be sure that a single hit of say a 100g projectile of a 20mm cannon penetrating armour and then exploding inside the tank would not always destroy the tank.

An AP projectile penetrating armor sprays red-hot or molten fragments of metal around a very small space. Those fragments ricochet and start fires. You DON'T want to be in that space. While a 20-30 mm projectile won't usually make the tank blow up or burn, it will damage the engine (if it penetrates the deck armor or ventilator grilles) OR kills or injures part of the crew (if it penetrates the turret or hull).

Even if it doesn't catch on fire, a tank with a badly damaged engine and/or a dead/seriously wounded crewman is going to retreat. Alternately, the crew might bail out, either because the tank can no longer move or because the drivers are dead, or on the reasonable assumption that more bad things are about to come their way.

In any case, the tank is as good as "dead" that day, even if the mechanics can later wash out the blood, fix the engine and patch the armor.

A simple fix to the ground vehicle damage model in IL2 would to be have three damage states: Undamaged, Immobilized/Partially destroyed (representing a crew kill or actual mobility kill) and the current damage model "Brewed up"/completely destroyed. No new damage textures are needed for Immobilized - the vehicle just stops moving.

This intermediate damage state is important, since the disabled tank remains a target for further attacks. That means that you and your allies waste ammo on a "dead" foe.

Pictures of knocked out WW2 AFV frequently show multiple penetrations. Example here:

http://i73.photobucket.com/albums/i2...ps736b6ffd.jpg