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.

[JtD]

Check out manuals given here:

http://www.lexpev.nl/manuals/germanyold.html

You'll find plenty of (German) ammunition manuals, for aircraft and artillery. German tank and AT guns often had two types of AP rounds - the standard AP round with explosive contents, and the "only use if penetration cannot be achieved with the standard AP round" round without explosive contents.

Naval artillery to my knowledge used only explosive AP rounds. Aircraft standard AP rounds were also explosive, with specials available. AP bombs were explosive. All this to the effect of generating splinters, which simply add to the damage of the splinters created from penetration. There were very few AP weapons to rely solely on kinetic energy in WW2.

Pursuivant, the shrapnel created by a single 20mm or 30mm round penetrating is by far not enough to reliably take out a medium sized or larger WW2 tank. You may get lucky, but to be sure you'll need more than one. Even to reliable do considerable damage, not the outright kill. It's one of the reasons small calibre AT guns in widespread use at the beginning of WW2 were replaced by bigger ones - even if you achieved penetration, you'd still need multiple hits to stop the tank.

Igo kyu, no matter the what participant gets damaged in the impact of the projectile, to remove the armour from the original position you need energy, and the amount is the same no matter if the projectile just penetrates, or easily. Assume a certain armour can just stop a certain projectile coming in at 500m/s. Now if the same projectile comes in at 600m/s, it will go through, but end up at 330m/s and at 800m/s come out at 620m/s, for the same loss of energy. The energy to displace, tear up, heat up the material has to come from somewhere, and it comes from the kinetic energy of the projectile.

What you are considering is solely the aspect if a round can penetrate or not. It's also important but not all. It is about the mechanical strength of projectile and armour. A thick, hard armour will break up an AP round, a thick, soft armour will stop the AP round intact and a thin hard armour will break up under the impact of the round. You are completely right that a penetration with both the armour and the projectile suffering significant damage is rare - but this has little to do with the energy required for penetration.

The reason why the standard AP round carries more energy is because it carries part of its energy as chemical energy of the explosive inside. This energy does not change with muzzle velocity and range, and will only be converted to damage after penetration. The 30mm round mentioned carries 14g of PETN (iIrc, don't want to look it up again). This equals about 50% of the muzzle energy of the tungsten core round, and with the projectile twice as heavy, the tungsten core round ends up with less energy than the standard AP.

[Pursuivant]

Originally Posted by JtD

Pursuivant, the shrapnel created by a single 20mm or 30mm round penetrating is by far not enough to reliably take out a medium sized or larger WW2 tank.

Agreed. But, my point about 20-30 mm AP rounds is that if they penetrate they're going to do a fair bit of damage to their local area - probably resulting in injury or death to a crewman or to some vital system. You won't get a "brew up" or "catastrophic kills" with a fuel or ammo explosion, instantly dead crew and a fiercely burning tank, but you will get a tank which can no longer operate offensively - which is what IL2 "kills" are actually measuring.

This is why I think it would be more realistic for IL2 to have three damage states = healthy, mobility kill/retreat/crew bailout, dead. No new damage textures are needed, you just have mobility killed/retreat/crew bailout tanks stop moving. The player might see a HUD message along the lines of "enemy tank damaged".

Additionally, there should be an option for "realistic tank armor" which considerably boosts the armor and durability for AFV, making them much harder to actually kill and bringing actual tank kills in the game in line with modern research into actual effectiveness of air-to-ground attacks. Perhaps doubling or tripling existing "panzer unit" scores for heavy tanks, and doubling panzer unit scores for medium tanks, would do it. Light AFV might get a 50% increase in panzer units, with no increase for soft vehicles.

That way, assault planes could still be hell on earth for convoys of soft vehicles, but not the "tank killers" they were purported to be.

Originally Posted by JtD

The reason why the standard AP round carries more energy is because it carries part of its energy as chemical energy of the explosive inside.

This is only true for APHE or similar rounds. If you're talking about standard AP, as was used at the beginning of WW2, the penetrator was just a piece of hardened steel. Soon after the war started standard AP was upgraded to Armor-Piercing-Capped (APC) where there as a soft metal tip placed on the tip of the shell to help it "grip" the armor rather than shatter on impact.

From there, there were a number of improvements to standard AP, such as API, APHE/APE/APEX, HEAT, APDS, APIT and APT. The Germans were the pioneers in developing APHE and APDS rounds. The British never developed a satisfactory APHE shell and mostly used just AP or APC for their tanks.

[Igo kyu]

Originally Posted by Pursuivant

The Germans were the pioneers in developing APHE and APDS rounds.

APHE possibly, but APDS? Did you mean APCR? I have read that APDS was fairly heavily adopted by the British, I thought it was even a British invention, though I can't back that up.

[Pursuivant]

Originally Posted by Igo kyu

APHE possibly, but APDS? Did you mean APCR? I have read that APDS was fairly heavily adopted by the British, I thought it was even a British invention, though I can't back that up.

My bad. You're right. I was working from memory. FWIW, Wikipedia claims that initial work on APDS was by a French company, but later the designers were evacuated to the UK and completed the work there.

As for APCR/Panzergranate 40, while the Germans were one of the first nations to develop it, shortages of tungsten meant they had to discontinue making it.