"HE vs Armour, a new method?" Topic

There has always been a lot of debate about how effective high explosive shells were against armoured vehicles. The typical arguments go 1) they could demolish smaller vehicles, 2) they couldn't penetrate but could cause all manner of soft-kills (destroyed optics, internal spalling, damaged tracks, ruined antennas, over-pressured crew cabins) or 3) they wouldn't even scratch the paint. Nevertheless, there are reports from WW2 of all three of these happening, including gunners specifically targeting the turret ring to dislodge the turret.

Now, the effects of explosives seem to change exponentially according to their weight. Blast radius, for example, seems to be inversely related (i.e. the blast radius of a Geballte Ladung is not six times the blast radius of a single M24 Stielhandgranate). When thinking about the effect of high explosives on armour, then, how does this rate for a general model (for designing games)?

The maximum RHA armour thickness (in millimeters) that an explosive shell can possibly penetrate on an perfect hit is equal to the square root of the explosive filler content weight (in grams). That is, a M24 potato masher on the deck of a vehicle can penetrate up to 13mm (a little more than a bullet). A Geballte Ladung can penetrate up to 32mm. A 7.5cm Sprg.Patr. 34 from a German howitzer can burst up to 25mm of armour. The big 10.5cm and 15cm guns can penetrate up to 43mm and 75mm respectively.

Does that seem like a reasonable representation of what might be called a penetrating hit?

Nope. Firstly, it's not all about penetration because spalling does horrible things to the flesh and bone items inside. Secondly, fragments from a near miss by a 15cm round are more than capable of taking out late 20th century armored vehicles

Results of a US Army test conducted in 1988:

"Researchers confirmed that the US 155-mm HE round was a reasonable surrogate for the Soviet 152-mm HE round.

An M109 155-mm howitzer battery using Soviet fire direction and gun procedures fired the test. The targets were manikins placed in fighting positions, US trucks, Ml 113 and M557 armored vehicles, and M-48 tanks.

Several different computer models were used to predict results. The test was fired three times using 56 HE rounds with point-detonating (PD) and variable-time (VT) fuzes.

The resulting effects on the trucks and personnel were close to model predictions. However, the effects on the armored vehicles and tanks were significantly higher than model predictions.

The model predicted 30 percent damage to armored vehicles and tanks; however, 67 percent damage was achieved. Fragmentation from the HE rounds penetrated the armored vehicles, destroying critical components and injuring the manikin crews.

In addition, the HE fragmentation damaged tracks, road wheels, and tank main gun sights and set one vehicle on fire.

Interestingly enough, none of the damage to the armored vehicles or tanks was the result of direct hits-all the damage was caused by near hits.

This test confirmed that US Army models did not accurately portray artillery effectiveness. Direct hits were not required to damage tanks and other armored targets."

TMP link

Well, to be fair, M107's have almost 250% more explosive content than WW2 era 155mm shells (for instance, the 15cm K Gr. 18), but it is interesting that fragmentation can penetrate tanks. In my paradigm, assuming the numbers don't go wonky at higher levels of explosive content, the modern M107 shell should be able to penetrate up to 117mm of RHA armour (which is more than a Tiger tank). The M60A1 (possibly the tank being they tested the rounds against in the late 1980's?) only has about 74mm of steel armour on the sides and around 140mm or better on the turret and front hull, so it seems possible. I do wish the article was more descriptive about what tanks were used and whether "67 percent damage" indicates penetration 67% of the time (or whether that includes external damages).

"I do wish the article was more descriptive about what tanks were used "

" The targets were manikins placed in fighting positions, US trucks, M113 and M557 armored vehicles, and M-48 tanks."

You should also bare in mind that penetration, or even significant damage, on an AFV may not be have been necessary. In many instance tank crews would bail out or withdraw from fire that had no real chance of causing a kill. This seems to have been particularly the case where the crews were inexperienced or in vehicles they knew to be vulnerable to enemy weapons. The crews weren't able to necessarily distinguish between A/T and HE fire, or to determine the calibre of the weapon. It was just a loud noise and a lot of vibration.

Both seemed to be a problem for Allied crews in both the Western Desert and Northern Europe. Many of the British tanks in the desert had particularly weak armour and I've read accounts of crews bailing out after a non-lethal hit on the assumption that they weren't going to be so lucky on the next shot. You have to remember that it was normal practice to fire several shells at a target even if an earlier one had been seen to strike. It was more important to make sure than the save ammunition. Similarly in Europe every enemy tank was a Tiger and every A/T gun and "88". It seems that Allied tanks frequently withdrew rapidly on coming under fire, just in case…

So the moral effect on the crew is probably rather more important than the millimetres of armour a shell can theoretically penetrate. This also offers and explanation for "well motivated" German crews continuing to fight immobilised tanks. They had confidence in the strength of the armour and their ability to continue to fight off the enemy.

as long as your friends agree then change the frontal arc to either 4 D8 or 3 D10…BTW the rating in the FonF book is for a T55M export version….The FSRD ratings do not reflect purely how thick the armour was or is,but the vehicles overall performance against contemporary oponenents.
Weapons ,fire control and Crew ergonomics etc. A lower frontal rating of 3D8 takes all of the above as well as other factors into account. …………..Mikey

Informative, thanks!

Ah, that makes sense then! Using my model, a 155mm M107 round could possibly penetrate the sides of an M48, but would more often cause external damage (as described in the live fire demonstration). "Armoured vehicles" like the M113, however, would likely be shredded for their thin armour. The 30.3lbs of explosive filler really packs quite a wallop.

I've lately been using a rough rule like this:
The ability of an HE shell to destroy/penetrate a vehicle is the diameter of the shell in mm divided by the thickness of the armor in cm. For instance, a 76mm shell hits a bit of armor that is 2cm thick: the chance of penetration is 76/2 = 38%. No idea how realistic that is, but it's easy to calculate, at least.

QUOTE "Does that seem like a reasonable representation of what might be called a penetrating hit?"

Presumably 'on target' plunging fire from long range artillery is devastatingly effective as it hits thin armour on top and causes all sorts of spalling, concussive and suspension problems in addition to increased likelihood of penetration (due to thin armour on top or even being open topped i.e. SU 76).

I suppose in terms of damage, you have to consider three things, a total miss, a nearby explosion and an on target explosion – the last one perhaps being the rarer in a barrage and the second one being the harder to assess resulting damage.

Perhaps some kind of formula based around weight of shell, weight of vehicle and whether open topped or not would give a consistent approach.

The ability of an HE shell to destroy/penetrate a vehicle is the diameter of the shell in mm divided by the thickness of the armor in cm.

That's a bit inelegant mixture of units for my taste. It could be expressed in unit-independent fashion with formula:

P = ((shell diameter) / (armour thickness)) x 10 %

Don't matter how thick your armour is, you shake a tank around enough with a HE hit or near miss and you make an omelette, be it human, electronics or operating systems, it's not about penetration.

That's a bit inelegant mixture of units for my taste.

Understandable. I do it that way because I already rate AFVs' armor in centimeters, and artillery rounds are normally rated by millimeters. But if that bothers you, sure, you could use your formula.

"well motivated" German crews continuing to fight immobilised tanks. They had confidence in the strength of the armour and their ability to continue to fight off the enemy.

That "confidence" came in no small part from their standing orders that a tank could only be abandoned if it was actually burning….leaving early could result in an unpleasant interview with the gentlemen in leather coats ;)

Thoi topic is still going in the modern world. Its about hitting or near missing as much as what it can do. Typicaly to survive an artillery barrarge you need to be proof from modern 155mm shels at 30m. This is on the basis that at typical loads, rates of fire and accuracy, thats about as close as you will get with a significant risk to the attacking force. There are still arguments about modere guns against tanks. The point is artillery guns are not optimised for fitting at moving targets over open sights. So if you do hit it it is likely to do some dammage. However the proability of a hit is small. Proably not wortyh a rule you will have bigger errors in you rules than this.

Anecdotal eveidence that it can hit is not prooof of it being likely or statisticaly significant. In WW1 they found a shell drilliled by cloision with another, but its not a rule that is relevant to a set of wargames rules. Travelling through an artillery barrage will potentially strip off ariels at normal fire dencities and proably damage sights (hence modern tanks have some protection.

If you must add something use the anecdotal data or the data you have but look carefully at the densities of fire reqiuired to achieve this if indirect or how you are going to get an artillery piece to account for lead and the relatively poor accuracy, as it is a low veocity gun relative to a tank gun.

Well, it's not necessarily plunging artillery fire that is the concern. In WW2 at least, field guns and tank crews did resort to firing HE rounds directly at armoured vehicles along a flat trajectory (when other options, such as antitank rounds or retreat, were not available).

This was done by leaving the nose plug in place instead of fitting the fuze, and proved quite effective. Sheer kinetic energy is enough to dislodge a turret with a 152mm shell, often blow it off completely.