"Defining Armor Penetration level and Compound Armor Angles" Topic

I don't think many people know countries' different penetration success criteria. Evidently, there is no international standard or measure I'm aware of.

To complicate it even more, some countries measure the vertical angle from the 90-degree vertical and some from the 0-degree horizontal. So when a statement claims Xmm of armor penetration at 30 degrees, is it 30 degrees from the vertical or horizontal?

Another factor is the horizontal angle. Armor thickness can vary because the true armor value to be penetrated is determined by the vertical (armor slope) and the horizontal angle known as the compound angle.

Also, how often does a projectile penetrate? This may come as a surprise, but the round will not perform 100% in the same way 100% of the time. So when we say something penetrates 100mm, it doesn't mean this round will penetrate 100mm 100% of the time, and it doesn't mean that it won't penetrate more than 100mm sometimes. I don't know of any formula that addresses that.

Below is an example of the differences:

The value given by US and UK sources is the number in which the round has a 50% probability of penetrating by US standards of penetration.

The value given by the Soviet sources is the number in which the round has an 80% probability of penetrating by Soviet standards of penetration.

Testing under very cold or freezing temperatures makes the armor more brittle and subject to cracking and penetration.

In games we normally determine the hit location. In tanks like the T-34s, Tigers, Panthers, and some Allied tanks, the turret side is bulged out to give more interior space inside and sticks out past the turret front or mantlet when targeted from the front.

The T-34/76 turret side armor, when hit at 90 degrees to the side, is 52mm sloped at 20 degrees. However, when hit from the 0-degree front with about a 70-degree horizontal angle it is 160mm according to the relative armor calculator here: link

According to the calculator, the compound angle is 71 degrees which would most likely be a ricochet as compound angles over 70 degrees normally result in a ricochet. If you look at the total area of the turret front, the turret sides account for 25%-30% of the total frontal area.

The gunsight and coaxial machine gun locations (in green) would present weak spots with armor less than the rated armor level.

These are some of the problems you run into when attempting to portray a more historical and realistic simulation of the armor on any vehicle.

What I've done is use the calculator to determine the armor thickness using the compound angle and chance of a ricochet for different targeted aspects (front, oblique, side, and rear). Since there are no calculations for the player it's no more difficult than any other abstracted system.

I also assign damage levels depending on the level of penetration. Penetrating 5mm less than the armor results in spalling damage. The targeted player rolls to see if the round ricochets.

Has anyone worked on something similar?

Wolfhag

I went through this process in the 1970's and threw it all away. Needless complexity in the pursuit of realism led to tedious procedures that killed game flow and enjoyment. It was an interesting mental exercise, but it did not make a better game. I do not mean to trash your efforts, if you find them valuable I encourage you to press on.

This level of detail may be feasible if using a computer to do the resolution of hit locaton in detail and the effective thickness without being more work for the players other than waiting for the resolution of each shot which tends to be a gating factor for using a single computer for moderationin games.

It's also unclear how much it adds over a reasonable approximation of the damage possibility of a weapon versus armor for a game that isn't specifically meant to simulate armor penetration specifics versus overall effectiveness in a combat situation, e.g. in winning the battle ;-).

Yeah I've used something similar in the old Yacquinto Panzer/Armor/88 set of boardgames. They've been updated by GMT games.

The games use an armour base of 1=5mm and a vehicle data card that gives the armour base for various angles around the vehicle and for level/rising/falling shots.

The data cards are fairly accurate although I prefer the older ones as they seem more accurate. I'd recommend referring to them as a guide and then see if you agree?

I can understand your frustration and confusion with the armour angles relative to horizontal or vertical. I usually use relative to vertical but it can be to the horizontal for, say, deck armour.

I also use an armour thickness modifier of 1 over the Cos of the armour angle, based purely on simple trigonometry. Imagine the armour as 2 parallel lines separated by armour thickness and tilt by armour angle.
Preaching to the converted probably :)

Hope this helps,

B

I generally weasel out of this by playing stand=platoon games, and guessing about the chances of stopping or destroying the platoon under different circumstances.

But strictly as a wargamer I'd use the uncertainty to limit the complexity. Have three or four bands of AT weapon and three or four bands of tank armor. One die roll with modifiers for weapon, distance and exposure determines whether or not you hit. A second die roll with modifiers for weapon, distance armor class and side exposed gives a result of null/immobilized/main gun out of service/destroyed. One or two rolls and on to the next tank. Anything more complicated, and your players will start side conversations, pull out a book or go off to the flea market.

Thanks for the feedback.

Please note regarding determining armor thickness:
Since there are no calculations for the player, it's no more difficult than any other abstracted system.

The details are transparent to the player. If one game uses armor thickness abstracted as a "6" mine would have a strength of 70mm based on how the compound angle formula modifies the armor. The player does not see or use the calculator so it's as simple and playable as any other system.

This level of detail may be feasible if using a computer to do the resolution of hit locaton in detail and the effective thickness without being more work for the players other than waiting for the resolution of each shot which tends to be a gating factor for using a single computer for moderationin games.

Without a computer, I've been using a simpler system to determine the exact hit location. Roll 2xD10 (1-00 result) and a D20 at the same time. The result graphically (no charts) shows the exact hit location hit (distance from the aim point), armor thickness (with compound angle), and behind armor system that can be damaged (ammo, gas, etc). Also, if the round ricochets from highly sloped or rounded armor. There are no special rules and nothing to memorize.

I understand it's counterintuitive to think that greater detail is just as easy as a highly abstracted system but sometimes it is.

It's also unclear how much it adds over a reasonable approximation of the damage possibility of a weapon versus armor for a game that isn't specifically meant to simulate armor penetration specifics versus overall effectiveness in a combat situation, e.g. in winning the battle ;-).

Yes, some games are designed to go into detail about penetration and damage and some are not or are highly abstracted. There is no right or wrong way to do it.

Aren't the nuances and comparisons of armor penetration versus armor specific to overall 1:1 AFV combat?

Platoon versus Platoon stands would be a much larger game needing a not-so-detailed system like figuring the Pk for different ranges against different targets.

After reading "WWII Ballistics and Armor" I wanted to simulate some of the historical nuances of ballistics, armor, and penetration as portrayed in the book in a playable way because that's part of a tactical 1:1 AFV combat I find interesting. What I mean by "playable" is making it just as easy as any other game.

I use this with my "OODA Decision Loop Game Engine" that eliminates traditional game rules and mechanics die rolling for initiative, activation, command points, turn interrupts, etc. You don't get bored and you can't walk away.

I use customized data cards like Yaquinto and GMT (Jim Day design) but mine are a little larger and have more detail. I use a completely different gunnery system too.

I've been playing this system at stores and conventions for 5+ years so it's not just an idea or theory.

About 5 years ago I showed the design to the president of a very large US game publishing company. He really liked the OODA game system but declined to publish it because it would take away from the sales of an established tactical AFV game he already has and the designer is a good friend of his.

Wolfhag

ITt is all about the level of approximation you are prepared to accept. Armour pneertration is a good example. You need to establich the compound angle the round hits the surface and which bit of the surface it hits. APCBC (Armour Piercing Capped Balistic Capped) worked better than basic AP for example. We looked at this topic VERY briefly. Problem is you also have some issue with terrain. Travelling on the side of a 1 in 10 slope would change the angles and possinly expose the turret to impact. So to be effcetive you would have to know the real compound angle for each shot. That requires real geometry. Do you use the model hill slope ot caluulate the actual slope at the [point on the model you whnt the fireing solution. How exact are yoiur hull down positions as that is what protects the hull at least im part form some rounds. A Uk study apparently noted about 1/3 of all hits were below 3ft. How well found or built protection would impact this value. Again facinating studies and hugely interesting but but as a set of wargames key paramters not one of mine except at the crudest level.

It a great study and I wish you well but personally as in all models there is a usefull level of approximation beyond which the gain in overall model performance does not improver despite far more computing power required.

UshCha,
You bring up a valid point which surprisingly has never been brought up in a game but can get complicated. Also, I've never rated hills for degrees of slopes other than to say it is too steep to climb.

The main issue is that the angle modifier is not linear. At 10 degrees it is a x1.02 modifier. Against a flat surface like a turret on a Tiger I or Sherman 76 the result is 1-2mm.

The 55-degree slope on the Panther glacis of 85mm is 150mm with a multiplier of 1.75.

A 45-degree slope on the Panther glacis of 85mm is 120mm with a multiplier of 1.4.

A slope of 30 degrees is a multiplier of 1.15 and 20 degrees is 1.06.

I think the real difference will be with vertical slopes of 45+ degrees.

My gun charts have hit chance and penetration in 100m increments. If players wanted to they could recalculate the armor thickness. An easier way would be to use the penetration value at 3/4 of the range rounded down.

If the scenario is on flat ground it won't be an issue. Depending on the scenario it may be. Ideally, you don't move up and over a hill because you skyline yourself.

When it would be an issue in my game is if you fired at a tank as it is coming up out of a ditch and its nose pointed about 45 degrees up. If the armor is 50mm a multiplier of 1.4 you get 70mm. Again, 3/4 of 70 = 52mm.

Overall I don't think it impacts the game negatively for three reasons. #1 it's a rare occurrence or no chance if on flat terrain. #2 by comparing the penetration to the stated armmor value it will be pretty clear if you have a chance to penetrate of not. #3 it will only affect armor with slopes of 40+ degrees or more.

The computing power is only two inputs on a calculator unless you want to get into doing something for a physics PhD paper.

So to be effcetive you would have to know the real compound angle for each shot. That requires real geometry.

As I said, all armor values have been pre-calculated and are on the data card. The players don't need to make any calculations or use math.

How exact are yoiur hull down positions as that is what protects the hull at least im part form some rounds.

A hull-down position exposes only the turret. A suspension down position (partial hull down) protects the lower hull and suspension.

Another issue is hitting the turret or hull roof with an armor of normally 10-15mm. Unless you are firing a gun with a muzzle velocity of 500m/second or less the angle of descent is going be be 2-3 degrees at typical ranges. With a height advantage, it can be more.

If you are measuring angles from the vertical (not the horizontal) it's going to be over 70 degrees which is normally agreed the angle an AP round will ricochet (WWII Ballistics and Armor). I think this has been proven in naval battles where rounds are effective against the deck (plunging fire) at 2/3+ of the maximum range.

With guns like the German 75L24, I have a hit negative location modifier which can result in a roof or deck hit. I use the same for Panzerfausts and bazookas too.

I use a D20 for hit location which is tailored for each vehicle. Generally, a 1-7 is a turret hit. If you look at the T-34/76 turret IIRC a 1-2 would hit the bulged turret side with 160mm of armor and a high ricochet chance. A 3-5 would hit the rounded cheek armor of 70mm with a small chance of a ricochet. A 6-7 hits the gun mantlet with an armor of 50mm (average it out) with a small chance of ricocheting.

Why do I do it this way? If you examine the turret, you'll see the 1-7 location roll is more historically accurate, playable, and has not had any complaints from players. Personally, I like the nuances of AFV combat, and if I can design in the detail and make it playable why not? There are dozens of highly abstract games that don't take this approach. So like many of you, I created my own.

Keep in mind, I play-tested the final version with a 14-year-old with a slight learning disability who has no war gaming experience other than tank video games. He caught on after 30 minutes without reading the rules. Don't be intimidated by the details or overly complicate the issue.

Wolfhag

Okay, before I say this I know it's not historical, but I play a lot of World of Tanks Blitz on my ipad and it's amazing what difference armour angles make to penetration. I love the game, BTW, and I'm endlessly fascinated and amazed by the amount of different calculations the server is making in 'real time'. Shooter to target angle (in three dimensions) and armour angle, with armour thickness increasing or decreasing with each degree of change; even auto bounce is included, as is overmatch.

However, in table-top games these calculations are impossible to do, so why bother trying.

In table top games (I play WW2 western desert) I'm more interested in the narrative of the battle and, frankly, ease of play.

Simple tables and a couple of d6 wins out for me over very detailed rules.

Once upon a time, I played rules from the Tank Battles in Miniature series (Quarrie & Featherstone), with different armour values for front, side, rear, of turret and hull with decreasing penetration values for guns over different ranges with variables for the type of ammunition being used and separate rolls for what type of damage and crew injuries were caused by any penetration; looking through inverted periscopes to get the ground's eye view of the target and all that. All great fun aged 14 but, life's too short. These days, I'm much happier with rules that follow the general K.I.S.S. principal – Keep It Simple Stupid.

No offence intended, whatever floats your boat.

If you want to see what I mean about WoT Blitz, go to the Blitz Hanger site. choose a tank, go to armour profile, press 3D image where you can manipulate the tank to find it's weak spots – if you don't know about this free site, I think you'll love it and be amazed by the level of detail.

Bear in mind that this site deals with tanks from Blitz – even the historic ones often come with in game, non historic, 'modifications'. E.g. you can mount a high velocity 10.5cm on a Tiger 2 – and if you play Blitz you would be an idiot not to!

I use a system that starts with the armor thickness in mm calculated with slope. I then multiply this by 1.4 as no shot is perfectly perpendicular to the armor facing. I use this as the general FP needed to penetrate the armor. For example; a panther tank has 80mm frontal armor but when including 55 degree slope this increases the effective armor to around 140mm. From here I multiply by 1.4 bringing the total effective armor to 196mm. Rounded up to 200mm.

I next assume that the odds to penetrate 200mm of frontal armor are low if the fire power is anywhere from 200mm to 300mm and the odds increase as the firepower gets greater. If firepower is greater than 2x the armor thickness there is no armor save as the firepower is too great.

This is a jagdpanther with the amazing, thick, sloped-armour – real monster with the 88 mm pak super-gun:

IWM – Jagdpanther

So – a geezer with a sherman knew he had no chance from the front – so he knocked out a track, spent half-an-hour flanking it and then popped it with three rounds.

Veejo:

IWM – Jagdpanther

I saw it in IWM Lambeth but I think the thing is now in IWM Duxford (Cambridge). Worth a visit.

PS1. I love all the armour thicknesses, slopings, calculations, etc. But a mobility kill and skilful tactics would appear to negate a lot of armour's advantages.

PS2. What about a top-attack from a P.I.A.T?

I've experimented with all sorts of rules tinkering. When I was much younger I tried detailed rules. A protractor and pointer was used in some of these.
Also did action points and phases.
Still use that with Feng shui. Works well when there's one character to one player.
Foam board and map pins for phase tracking.

I saw a JagdPanther at Bovington. It's an awesome vehicle.

The game that I think best portrays the nuances of armor and penetration accurately is Panzer War: panzer-war.com

The website also covers many of these aspects in greater detail and corrects some mistakes from other publications. He used "WWII Ballistics and Armor" formulas to get the armor strengths and determine penetration.

I made a customized spreadsheet for my gunnery to determine chances to hit.

What about a top-attack from a P.I.A.T?

Any weapon with a low muzzle velocity can have the ability to hit the turret or hull roof. The angle of elevation when shooting will generally be the angle of descent at the target and sometimes steeper.

The muzzle velocity of a PIAT is 76/mps. It does have a bubble-level sight for indirect fire which would almost guarantee a top hit but with poor accuracy.

Looking at the PIAT front and rear sight at 110 yards it appears to fire from an elevation of 10 degrees. The angle of descent is probably no more than 15 degrees so not much chance of a top and and even if it does the angle may be too shallow for the round to detonate.

The Panzerfaust is 35-45mps depending on the model. I watched a training video of a Panzerfaust firing and it looked like the angle of descent was about 40 degrees so a good chance for a top hit not that it needs one as it will penetrate any armor on a tank but they did have about a 10% dud rate.

Wolfhag