Behavior of AP shells

[womble]

I thought AP-shells (HEAT) detonated on impact, and that it's the force of the explosion that penetrates the armour?

AP != HEAT

"AP", short for "Armour Piercing", while it could, potentially be a catchall for rounds designed to defeat armour, is generally taken to include rounds which do so by Kinetic Energy, delivered by a high density, tough projectile travelling really quickly (about MACH 2.5 in WW2, pushing MACH 5 in modern MBT guns). There are many variations of "AP", covering aspects like a ballistic cap (to improve ballistic performance), discarding sabots (to make the muzzle velocity of the round higher by reducing the mass of the projectile, while preserving the cross sectional area of the base for the propellant to act upon, and at the same time improving streamlining and terminal effect by making the projectile have a smaller CSA. Some AP rounds have a small (approximately grenade sized) "burster charge" with a fuse that will only trigger if the shell hits something hard and decelerates violently, to improve the damage done to the interior of the target; these are sometimes referred to as "APHE", though some Grogs seem to repudiate that label.

HEAT stands for "High Explosive Anti Tank" and uses the effect of a shaped charge to penetrate the armour. This only relies on the chemical energy stored in the HE, so the velocity downrange of the round is relevant only in so far as it's easier to hit things if the flight time is short.

Have a Google for "Armour Piercing" and "HEAT round" for more on the differences.

[Pandur]

also take a look at "HESH" while you at it. it doesnt form a penetrator, so mostly works like you imagined.

HEAT "forms" a penetrator while AP shot in its various forms "is" a penetrator already.

[Vergeltungswaffe]

More than once, I've seen a shot from a T-34/85 hit a Panther, ricochet into the air and come down, making a small explosion when it hits the ground. Assumed that was the burster charge.

[Apocal]

By the way, if anyone has a save demonstrating this, please PM me. It will save me some time.

Would further saves help?

[Saferight]

Heres some videos i have on youtube of the penetration effects. Just to to add to current discussion not just a shameless plug

https://www.youtube.com/watch?v=ZjHQOL_PwB4

https://www.youtube.com/watch?v=63mqDZaLoSc

[Amizaur]

Once in CMBN I did some tsts, in which I managed to penetrate the sides of several (like 7 or 8) halftrucks positioned in a row . I used 88L71 Pak. And I believe it would be possible as well in real life . Penetrating sides of 3 Sherman tanks in a row (this was also possible in CMBN using 88L71, IRC) would be less likely in real world.

[Amizaur]

AIUI, it's been said that if the first target struck is destroyed by the round, the armour on the exit side isn't counted for that round, so that could explain the 76mm through-and-throughs on PzIVs.

Maybe it could be fixed by introducing a 0.1s delay in changing the vehicle status to "destroyed". This way the shell would manage to leave the vehicle trough the other wall ( legally penetrating it) and vehicle would become actually destroyed 0.1s later.

Two things to take care on - first, that only the "first" penetration txt for a given vehicle is displayed, and not the second (about penetration of the other side).

Second thing - that the "second" penetration from inside out, does not add damage to the vehicle itself and don't cause additional casualities among the crew.

P.S. (warning - semi off-topic) The amount of damage to the crew caused by penetration of tank armor should be increased as well, IMO.

The average number of wounded crewmembers should be doubled at least, the number of killed ones shoud be increased as well, especially for deadly APHE shells (like 88mm PzG39) or high-callibre high-energy APHE like 122mm APs.

I recall a note by some German high-rank panzerwaffe officer about how Tigers are not anymore invunerable after intruducing by Russians 122mm guns. That lone Tigers should not come to the exposed positions on top of the hill to "take a look" because it's become deadly dangerous - lately some Tigers tanks were lost in such sitations penetrated by 122mm AP shells, and those were total losses, only one crewmember survived one tank, the rest were lost with whole crews. So it seems that 122mm AP was quite deadly when it fully penetrated - and it's understandable.

But not so in CMRT 1.0. Average number of killed among cremembers from Panthers penetrated by 122mm APs (1000m) are in order of ~2,5 crewmembers/shot for side penetrations and only ~1.8 killed crewmembers/shot for front penetrations.

Chances for catastrophic ammo explosion (resulting in all 5 crewmembers killed) were ~25% for side penetrations and ~12,5% for front penetration.

In both cases the difference between front and side pentrations is visible, I guess that in side case of penetrations (thinner armor) the penetrating shell retains greater part of it's kinetic energy and it's taken into account in "damage" calculations.

Average number of wounded crewmembers was much smaller than for killed ones. About 0,36 for side penetrations and 0.31 for front penetrations, no visible difference between front and side value. IMO the average number of wounded crewmembers should be at least twice the value of killed ones.

All above values are based on a sample of 120 penetrations total (53 side, 67 front) so far.

Prelminary 122mm AP vs PzIVH test shows that number of killed is higher than in case of Panther - but again I would expect much more 100% casulaity instances - in cases where the 122s AP big 156g RDX burster triggered and worked as designed...

[John Kettler]

Amizaur,

I suspect that, were the Russian tank/SP crew casualty when hit breakdowns available, we would find the average loss per tank/SP hit would be higher there than for US and Allied crews in Western Europe, specifically because the Russian armor, save for late model Lend Lease Shermans, lacked not only wet ammo stowage, but even armored bins for the ammo, as found, for example, in the German Panzer III. The Russian accounts I've read strongly indicate the usual outcome when a tank got hit was most of the crew became casualties, often killed outright.

Lyubov Pakhamova, combat medic (miscategorized under Others)

http://english.iremember.ru/others/14-lyubov-pakhomova.html

Fair Use

"I wasn’t able to help my front line comrades in one battle. I still feel the pain of my helplessness. And that’s how it happened.

Ours started the attack, but it got “choked”. Then four T-34 tanks were sent to support the infantry. Everyone was joyous. And all out of a sudden – there were four great torches: the fascists hit all our tanks! No one scrambled out of three tanks at all. And a fiery ball rolled out of the last, fourth one… The Germans opened a storm of fire on him. I rushed to the burning tanks from the trench, but the soldiers stopped me and dragged me down: there was no one to help already…

I thought I would go mad: my first best school friend and fiance lieutenant Yevgeny Ivanovich Domeratsky was burning in the tank, and I couldn’t help him at all."

From later in her account, it's clear she's talking about Kursk, since she says she doesn't go to veterans meetings at Prokhorovka. The crew losses are wholly in accord with, if not worse than your expectations.

Information in this very good WoT post indicates the average American crew loss in Western Europe for a tank penetrated by gunfire was one KIA and one WIA. As such, it is a shocking contrast to the near annihilation of the T-34/76 crews I cited in the Russian female medic's account. That said, the Russian medic's eyewitness account is but one incident, whereas the analyses cited below are based on thousands of penetrating hits vs US and Allied tanks.

On Allied Tank Casualties in the ETO and German AT Weapons

http://ftr.wot-news.(usual)/2013/12/26/on-allied-tank-casualties-in-the-eto/

Regards,

John Kettler

[Amizaur]

Here are some descriptions of efects on crew in the Western theatre (in British tanks)

http://www.armchairgeneral.com/forums/showthread.php?t=142584

Be warned, not a pleasant reading

And this also may be worth looking into, I'm going to try it: http://payhip.com/b/DO4I

T-34's interior was full not only of unarmored ammo in boxes and in ready-racks on the walls, but also there were unarmored fuel tanks inside. Detonaton of APHE shell inside (or penetration of those fuel tanks located over the tracks) had usually catastrophic results.

My suspicion is that most (not all) of the tankers that survived destroying of their tank (to write memoirs we read) - survived just because the APHE shell failed to detonate inside.

Either because of fuze damage during penetration of the heavily sloped front armor plate, or because of simple malfunctio or sabotage (remember that those shells were produced by slave workers). So only the kinetic effects of penetrations occured - and descriptions like "the driver was killed instantly, the gunner lost both legs, I was only lightly wounded" fits well to penetration by pure AP projectile. I believe that description of penetration with detonation of APHE burster (especially 88mm one) in crew compartment would be little different (explosion, likely lost of consciousness, black smoke inside tank, burns). Even if it didn't ignite the ammo or fuel, it could kill the whole crew with simple overpressure, if anyone survived he would be burned. I do not want to say that this would be not survivable, but killed&wounded ratio would be much higher than in pure kinetic penetration, the chance for ignition of ammo/fule and explosion or fire - much higher, also psychological effect on surviving crew much greater - after penetratio the crew compartment would be hot, full of post-explosion fumes and black smoke, every easily flammable substance like paper or crew clothes could be smoking or even burning. I guess that in such situation 90% of crews - even if survived without wounds - would think only about escaping from this steel coffin and breath fresh air.

I would also reccomend that when calculating the chance for crew wanting to immediately get off from the penetrated vehicle - few factors should be considered beside the morale.

First - obviously - what is the chance that the tank will be penetrated again in few seconds and if they can do something about this, or not. I know it's very hard to estimate in a game-engine terms. It depends on how the crew feels about strength of their armor (Tiger crews less likely to escape from tank after single pentration than PzIV or T-34 or Sherman crews) and what guns the enemy have. But maybe it could be estimated somehow, even if it would be a single coefficient for a given vehicle in a given theater/period.

Second - very important one - if the crew see the vehicle that penetrated them, or not.

Crew that knows the threat is less likely to panic than a crew in a tank suddenly penetrated by unknow threat. Taken by suprise, and not knowing what hit them (often from the side), the crew is really likely to panic.

Such picture emerges from read of various tanker memoirs and descriptions of their reactions for tank being hit/penetrated in various situations. This picture says, that most frequent reaction for tank being suddenly and violently penetrated by enemy shell - was to get out as fast as possible, and only then asses if the threat was real or not, if the tank is damaged/burning or in working state. If there is no more incoming fire, and the tank is ok or can be saved, the crew would get back in or put out the small fire and get back in. But only after escaping first . Immediate evacuation from tank (call it a panic) was almost guaranteed, if the penetration was sudden, by an unknown and unseen enemy, that can not be fought back and probably is just reloading it's gun to shot again...

Of course it happened that the crew stayed inside and tried to continue fighting (even if some crewmembers were killed) but it was more rare than getting out.

One another think I would like to see simulated is few seconds of a "shock" state for the crew after high-energy penetration of their tank. Even if they survive and want to stay inside and fight back, they should not react immediately, in most cases they would need a moment to recover/rally and return to performing their functions. I remember such "shocked" state for most penetrated tanks in CMx1 and it worked very well. I didn't notice anything like this in CMBO/CF...

[jtsjc1]

Very interesting reading. Its pretty clear the high velocity 75mm KwK 42 was an excellent tank killer. Reading AARs even crew members not killed were severely injured by fragments so the round not exploding wasn't always good news. Thanks for the link!

[Amizaur]

The 17 pounder gun was also excellent tank killer, even though it's shells lacked the burst charge. High percentage of German tanks penetrations, especially from the side, resulted in instant explosion of the hit tanks. The kinetic energy of the penetration was usually enough, because the shell usually penetrated with great excess of energy and entered the tank interior at high velocity.

Of course adding a burst charge would make it even more lethal, especially in cases where it barely penetrated.

75L70 had little less energy than 17pdr, but the shells had a small bursting charge praised for it's effectiveness.

88L71 had both greater velocity, greater energy and quite big burst charge. Penetrations by this gun had to be awfully lethal...

Same for Russian D-10T 100mm gun - high velocity, big kinetic energy and a burst charge.

The 122mm D-25T gun had average velocity, but greatest kinetic energy, and a huge shell with big HE burster.

[jtsjc1]

The 17 pounder gun was also excellent tank killer, even though it's shells lacked the burst charge. High percentage of German tanks penetrations, especially from the side, resulted in instant explosion of the hit tanks. The kinetic energy of the penetration was usually enough, because the shell usually penetrated with great excess of energy and entered the tank interior at high velocity.

Of course adding a burst charge would make it even more lethal, especially in cases where it barely penetrated.

75L70 had little less energy than 17pdr, but the shells had a small bursting charge praised for it's effectiveness.

88L71 had both greater velocity, greater energy and quite big burst charge. Penetrations by this gun had to be awfully lethal...

Same for Russian D-10T 100mm gun - high velocity, big kinetic energy and a burst charge.

The 122mm D-25T gun had average velocity, but greatest kinetic energy, and a huge shell with big HE burster.

Looking at some of the pics showing 122mm penetrations the fragmentation also had to be devastating considering the slab of armor it would throw into the tank. Same for the 128mm.

[womble]

Of course adding a burst charge would make it even more lethal, especially in cases where it barely penetrated.

I don't think that's quite a given. AIUI, the burster charge was omitted from British-designed AP, generally, to improve penetration, so if the round without burster "only just" penetrated, it might not have made it inside had a burster charge lightened or weakened the shot.

[Doug Williams]

All I have is anecdotal evidence from my own battles, but I am convinced that the amount of casualties from deflected AP rounds bouncing off armor and injuring nearby ground troops is inconsistent with reality. It is almost as if deflected AP rounds suddenly turn into mortar shells.

[womble]

All I have is anecdotal evidence from my own battles, but I am convinced that the amount of casualties from deflected AP rounds bouncing off armor and injuring nearby ground troops is inconsistent with reality. It is almost as if deflected AP rounds suddenly turn into mortar shells.

I have to agree. Burster charges were grenade-sized for the most part, and trying to break up a tough, designed-for-integrity (rather than designed-to-break-up-into-wounding-fragments) container. Nasty inside a tank's confines, where the largish lumps still have a lot of intrinsic velocity to help rattle them around amongst the squishy components of the system, but they seem to be about as lethal, exploding outside the target, as a "proper" grenade. I reckon, though I'm entirely happy to be shown I'm wrong, that the burster should detonate at the ricochet point, too, not at the terminus of the shell's flight, or, if the ricochet doesn't set the fuse off, nosing down into forest loam wouldn't, either.

[Michael Emrys]

Hmmm, does anybody know offhand if burster charges had a built in delay in the fuzing? My guess is that if there was a delay, it wouldn't be much of one since you would want it to go off before the round could possibly exit the vehicle.

Michael

[Amizaur]

In German shells it was not fixed delay fuse, but instead a "gone through" detector.

It was armed at launch, then triggered by sequence of great decceleration followed by lack of decceleration during penetration of armor. As soon as the shell penetrated and entered the interior of the vehicle, the spring in the fuse was released and the charge detonated. Not sure how far it could fly behind the armor in the time the spring moved, but probably it was in order of half a meter to one meter, depending on shell speed.

The minimal thickness of armored plate that would trigger the fuse was about 20mm (or little more).

The fuse was said to be very effective and reliable. On the other hand, it was a mechanical solution that could malfunction (especially if mass produced with poor materials by slave workers) and it tended to fail after penetration of highly sloped armor - the enormous side acceleration experienced by the shell caused some moving parts inside the fuse to get stuck/jammed and the fuse didn't work.

Other nations fuses used a simple fixed time-delay IIRC. Not always timed correctly, sometimes they tended to detonate during penetration of the plate.

[Michael Emrys]

Thanks for the interesting info, Amizaur.

Michael

[John Kettler]

Amizaur,

Well stated, but incorrect. From: Thomas Jentz “Tank Combat in North Africa, The Opening Rounds”. Schiffer Publishing Limited, 1998, cited in my Post No. 3 in a very contentious and informative thread. (The partial penetration referred to below means that half of the APHE shell body has penetrated into the fighting compartment before detonation. ArgusEye has thoroughly studied German AP shell fuzes and can go into enormous levels of detail, to include the divergent paths taken by the Allies and the Germans on fuze design).

http://www.battlefront.com/community/showthread.php?t=106028

(Fair Use)

"AND from page 54

4.1.2.2 EFFECT AFTER PENETRATION

In all calibers of 3.7 cm and above, the normal armor-piercing round designed by the Germans contained a high explosive filler with a delay fuze. Penetration of a British tank by a German armor-piercing shell frequently resulted in crew members being wounded as well as destruction of the tank by causing irreparable damage or by setting it on fire. Not until 1942 did the British investigate the cause of fires in the tanks and began to install armored bins to protect the ammunition.

As recorded by Major G. B. Jarrett in May 1942: The German projectiles which have caused the greatest amount of damage to Allied tanks in the Western Desert campaigns have been the A. P. -H. E. type in 47 mm, 50 mm, 75 mm and 88 mm respectively. These projectiles at long ranges need only attain a partial penetration and the explosive charge can complete the destruction of at least the tank crew. At closer ranges the destructive effect is very great, where in many cases destruction of the tank is permanent.

When the 7.5 cm K.Gr.rot Pz. was fitted to an American casing and fired from the 75 mm M2 gun, in May 1942 Lt.Col. Gruver reported: Each German AP-HE round fired may safely be presumed to have put the tank out of action. In this connection it was noted that the fuze functioned perfectly, that is to say it functioned only after penetration and then always in the fighting compartment where the most damage is done. Parts also frequently penetrated into the engine compartment."

I would add that Lt. Col. Gruver erred in his phrasing, in that he left out the part in which the APHE projectile hits the tank and penetrates!

Major Jarrett was Ordnance Corps liaison to the British in the Western Desert. He was so intimately involved in such matters he personally examined numerous tank carcasses, operational records, test results and was decorated for radically improving U.S. supplied 75mm ammo prior to Gazala by pulling our projectiles and inserting pulled German PzGr 39--after harrowing machining of the driving bands of the spin armed shell! Jarrett was also the man who recognized the lethality of the 88, made it his business to find one and ship it back to the US for technical evaluation. This was the core of the Aberdeen Proving Ground Ordnance Museum.

Regards,

John Kettler

[Amizaur]

Thanks for the very interesting article. Again the effectivenes of PzGr39 fuse is mentioned. I'm not sure about what incorrect info you said.

If it was about the phrase "high explosive filler with a delay fuze" in the article, then the phrase is most likely incorrect. I'm not sure what kind of fuse the 7.5 cm K.Gr.rot Pz had, but all the PzGr39 type shells had mechanical "decceleration-lack of decceleration" fuse, and NOT a "time delay fuse".

I need to mention that the 7.5 cm K.Gr.rot Pz had a very larhe HE burst charge, 80g of HE. Charge of this size - seem from the article - has disastrous effects. Later 75mm Pzgr39 had much smaller charge of 19g and were less deadly, although the charge still increased their effectivenes. 88mm PzGr39 shells had much larger burst charge, comparable to the one of 7.5 cm K.Gr.rot Pz.

Time delay method was probably worse, because it was hard to set one single delay time that would be correct in all situations. When the shell was penetrating with great excess of penetration power and retained most of it's initial speed inside of the vehicle, too long delay would cause it to detonate too late, when it gone trough the other side. On the other hand, a short delay time would not work in cases when shell barely penetrated, the penetration process was long and the shell "almost stopped" during the process. It would most likely detonate during the penetration of armor, then. Fine tunning this delay time to work well in most cases, was something than not all nations managed to achieve during the war. Some types of time fuses tended to go off too early, destroing the shell when it was still penetrating, some other may have detonate too late, when the shell gone completly trough the tank (especially in cases of tank side armor penetrations - when high shell speed was retained).

[John Kettler]

Amizaur,

You're welcome! In an earlier version of the post, the one I screwed up by confusing tabs and going to another site on the post tab, wiping out my longish post, I talked about our German AP ammo grog, physicist ArgusEye, who's also very good at tank optics (used to collect them). He's read the pertinent technical discussions, the analyses and scrutinized the fuze blueprints in the Germans' own ordnance papers from the 1930s on and says they miniaturized their fuzes after cleverly coming up with a way to deal with the fuze jamming impact crunch, whereas the Allies, in trying to solve the same problem, built bigger, heavier and stronger fuze components.

Where I'm saying you're in error is the assertion that the fuze for German AP shell routinely detonates a 0.5-1m inside the fighting compartment. As the quotes show, at longer ranges, at least, even a partial penetration into the fighting compartment was sufficient to trigger the fuze and wreak havoc on the struck tank and crew.

On the other end, a really close, therefore, high velocity, engagement vs light armor, as in the M5 vs 88 case I presented, can defeat the fuze for lack of enough resistance to initiate it. I've seen another example in which a US halftrack in Tunisia took an 88 AP shell clear through from front to rear and out the back. Am not sure how it missed the engine, or didn't detonate if it did hit it solidly, but the projectile entered the fighting compartment, went right over the transmission hump and, running smack along the drive train main axis, entered the front of the fighting compartment, where it skimmed barely over the floor before exiting through the rear.

The shell never detonated, but it wrecked the halftrack from one end to the other as it passed through. Guess the Stuart crew should be glad that visitor didn't stay long! I recall reading nothing about what casualties were inflicted on the crew of the halftrack.

Overall, I think the terminal engagement phase wasn't as cut and dried as you seem to think. Offhand, I know of no data collected by OR teams or other means during the war to determine depth of penetration into the fighting compartment when AP shell burst occurred. The focus was on a) getting through the armor and making sure the fuze worked as designed once the projectile had (at least partially, in the German case) passed out the back side of the armor struck. If both were the norm in tests, and the AP shell worked in combat, then the item you cited became a nonissue. The Russians were quite anal about terminal ballistics, and in all the stuff I've read and seen, most recently at the fabulous, ultra groggy Archive Awareness site, I don't recall seeing a single mention of how far an AP shell penetrated before detonating. There, you can read the translated, formerly Top Secret firing trial reports for yourself.

Archive Awareness

http://tankarchives.blogspot.com

Regards,

John Kettler

[Amizaur]

"Where I'm saying you're in error is the assertion that the fuze for German AP shell routinely detonates a 0.5-1m inside the fighting compartment. As the quotes show, at longer ranges, at least, even a partial penetration into the fighting compartment was sufficient to trigger the fuze and wreak havoc on the struck tank and crew. "

Now I understand . The 0.5-1m was just an rough estimate how far a fast-flying shell could go inside of tank before the fuse works - of course this distance would be different with different terminal velocities, in many cases a slow shell could detonate just centimeters after entering the crew compartment. The actuall distance is not really importans as long, as it's not more than width of the tank . I only wanted to say that there had to be some minimum reation time after the fuse was triggered, needed for the spring to relax and for the firing pin to move and strike the cap.

There were instances of German shells detonating INSIDE the internal over-the-track fuel tanks of T-34 tanks, with catastrophic results. Shell came trough over-the-track armor, got inside the partially-empty fuel tank and detonated inside. If the shell had average or large burst charge, it usually exploded the fuel fumes blowing up the fuel tank and destroying the whole tank...

On the other hand, if a 75mm PzGr with only 17g of HE detonated inside a full fuel tank, it would set the tank on fire but the fluid would actually help absorbing some of the blast and shrapnel.

A description of a VERY interesting test here:

http://tankarchives.blogspot.com/2013/07/gas-tanks-fires-and-explosions.html

edit: the "working times" for firing pin assemblies in firearms seem to be in order of 2-20ms. M-16 assault rifle firing pin works in about 5ms, a good fine-tuned firing pin assembly can be less than 2ms. Let's calculate how far a shell could fly in that time.

Fastest 1000m/s shell can only move 1m per 1ms . If we assumed that speed of Pzgr39 firing pin was similar to some quick rifle firing pins (so in order of 2ms), then a fast shell that has penetrated some light armor and slowed down to let's say 400-600m/s could cover 0.8-1.2m in 2ms time of 2ms. If the shell after penetration slowed down to only 100m/s then it could go only 20cm in 2ms time. So barely penetrating shells could easily detonate just after entering the tank interior, fastest one could cover about 1.5m inside, before detonating.