"WWII rules that cover 'shatter gap'?" Topic

Anyone know of a rule set that attempted to deal with the phenomenon (had to use spell checker on that one!) of 'shatter gap'?

e.g. I'm sure I read about 2pdr uncapped shots in the desert succeeding at x range, then failing at closer ranges before succeeding again at very close range. The reason given from memory was the shells could not handle strikes at high velocities and broke up against the german armour. (I'm sure face hardened armour came into this as well?)

I'm asking because the usual rule sets assume gun performance gets better at shorter ranges and because my 'perfect rules set' will one day have to cover this.

Mitch.

The Final Combat rules deal with this phenomenon, and are very detailed throughout.

Last I heard was that the "shatter gap" theory was dead. Even Lorrin Bird & Robert Livingston who were some of it's biggest proponents have admitted that they were wrong and there is no evidence that it exists.

I use to visit AFV News a lot a few years ago and there read Lorrin's post where in he admitted that the evidence that they claimed to have supporting the theory was flawed and that the Shatter gap didn't exist.

jdg

As a metallurgist, I can't think of any physical reason why a projectile would consistently behave in this manner.

jdginaz wrote:

Last I heard was that the "shatter gap" theory was dead. Even Lorrin Bird & Robert Livingston who were some of it's biggest proponents have admitted that they were wrong and there is no evidence that it exists.

I use to visit AFV News a lot a few years ago and there read Lorrin's post where in he admitted that the evidence that they claimed to have supporting the theory was flawed and that the Shatter gap didn't exist.

Could you provide a link, please?

If shatter-gap as a phenomenon really does not exist, then it might be a good idea to pass the news on to the people who wrote the STANAG on armour testing (STANAG 4569, I think, I can't find where I put my copy down).

You might also get in touch with Roberson, Hazell, Gotts and Pickup, and let them know that they should withdraw their paper "The effective hardness of hot pressed boron carbide with increasing shock sress", for they seem to believe in the existence of shatter-gap on the basis of laboratory observations.

All the best,

John.

Rich Bliss worte:

As a metallurgist, I can't think of any physical reason why a projectile would consistently behave in this manner.

Adiabatic shear stress bands.

As I understand it, anyway, for I am not a metallurgist.

All the best,

John.

Just played a game a couple of weeks ago where this was inserted as a house rule for the game.
It was a 1940 scenario with invulnerable Matilda's lumbering around, (apparently) impervious to anything the germans could through at them (no 88's). We had a (rather unscientific) rule that their 2pdr rounds failed 30% of the time…so the Germans would hammer away and bounce off the Matilda's and the Matilda's would hit the 38ts and PII's expecting to slice through them only for the round to fail.
Fairly pleasing results, in he end the Germans had to manouvre and hit them with 20mm (high rate of fire) and degrade the British tanks via critical hits.
As I said, not terribly scientific, but made for a game which certainly felt it had the right flavour.

link

Shatter Gap is a real phenomenon.

I apologize for not making myself clear. I understand the phenomena from a standpoint of increased variation of results and of course the actual physical causes. The point I tried to make is that the factors which cause it to occur are not sufficiently quantifiable and controllable in the field and therefore not able to be represented in a set of rules above and beyond actually "rolling for penetration"

Rich Bliss wrote:

I apologize for not making myself clear. I understand the phenomena from a standpoint of increased variation of results and of course the actual physical causes. The point I tried to make is that the factors which cause it to occur are not sufficiently quantifiable and controllable in the field and therefore not able to be represented in a set of rules above and beyond actually "rolling for penetration"

I rather doubt that any of the factors influencing armour penetration are sufficiently "quantifiable and controllable in the field" to make wargames rules on the subject anything but (to use a technical term) a SWAG. A depressing thought, given that throwing a projectile at a plate and seeing if it goes through is almost the simplest act of war known to man, by the lack of worthwhile information has never stopped wargamers writing rules for it. And the game effect of shatter-gap is pretty obvious; a high proportion of successful penetrations at a longer range than one at which most hits fail against the same armour. I can't recall ever seeing a set of paper rules with such an effect included. However, while messing about with Dehn's penetration formula, I did manage to convince myself that you could get a shatter-gap curve that looked OK by eye simply by reducing expected penetration by 1% per m/sec of striking velocity over 750 m/sec, up to a maximum of 50%. I believe that 750 m/sec is about right for steel projectiles, and it would be the sort of velocity 2-pdr (especially with AP HV) or US 76mm guns would be achieving at close ranges.

All the best,

John.

"Anyone know of a rule set that attempted to deal with the phenomenon (had to use spell checker on that one!) of 'shatter gap'?"

Please list them… Atleast I will know not to buy them! ;-)

Did the Germans know of this "scatter gap", other than vaguely? Did they use this knowledge in the field?

If they didn't, then you will get a very gamey result by adding it to your rules. German tanks will close to the worst range for the Brits and then hover, knowing it is the ideal point.

Unless you can show that the Germans did that, then adding the scatter gap will decrease the accuracy of your rules, because it will stress a minor thing like technical accuracy over a major thing like how people actually fought.

Please list them..So I know to buy them. None of this stuff is that hard to model in a game nor would it make one unplayable.

IE. link

NOw the ranges given there would be easy to model those guns shooting at those tanks at that range wont have an effect even if the shot hits. Far unplayable. Simple rule to cover a technical issue that would have an effect on the battle.

I agree with Rich. A game that has to have an unnessary rule specifically for that is not for me. You roll your dice, crap score, you miss. Who cares why? Wind, dud shell, shatter gap, gunner ate bad eggs for breakfast – in a game circumstance it matters not a jot. That is the real point. Good on you if that is what you want out of a game – but you'll bore the off everyone who wants to shoot stuff with their tanks. No, I do not play FoW.

I play with it and everybody has a blast shooting up tanks. What isn't fun is watering everything down till its Yahtzee. To many systems make dice the game. I want the battle to be the game. The fun is recreating the reality.

I wouldn't try to model it in shells because you will end up only applying it to shells that it has been identified.

There may be many shell and shell types where it happens but the owning military didn't realize it or didn't publicize it.

Many weapons systems had to be guessed at. Incomplete data on OOb and performance has been used before. Take the available data and model that parts known easily.

The point Supergrover is that it is pointless to have "accurate" rules on some technical point when other equally important matters are mere guesses. In wargames rules effect is everything, and causes are nothing. (This is the curse of so much of Economics -- precise calculations based on guesses are no better than guesses.)

That has nothing at all to do with making it a game of Yahtzee. If anything a very technical ruleset with no concentration on C3 is the dice game, since it becomes a matter of line-'em-up-and-shoot. A simple ruleset concentrating on tactics and C3 is the one that introduces strategy.

Weapon performance influences tactic. The fact you have a M1a1 76 mm and can do a thing to a Tiger close up means your tactics will be to stay away. The weapons of some other guns are opposite so the tactics revolve around how to employ your weapons to the exploit there advantage. When games really on dice to "abstract" these things, it allows for exploitation of rules and games hinging on single die rolls.

"Weapon performance influences tactic. The fact you have a M1a1 76 mm and can[sic] do a thing to a Tiger close up means your tactics will be to stay away."

Which is what most rules achieve without pedantry.

"When games really[sic] on dice to "abstract" these things, it allows for exploitation of rules and games hinging on single die rolls."

So do you just point at a tank and say 'bang, you're dead'? Or; Do you roll multiple dice each turn to convince yourself that you are simulating "real" conditions? It is all abstract champ.

Certain things you can model with abstraction. Who knew that the 90mm HVAP could be broken up by passing through armor as thin as 1/4"? Or even the 90mm T-33 shot but not the 57mm AP shot by 1" armor at high velocity?

Panzer War is probably one of the most detailed rules around. But at some point it has to cover the rest of the ground by abstraction.

The problem with modeling things like this is that the underlying parameters are unknown. What the 'scatter gap' phenomena is covering is an unpredictible variation in penetration. At any moment in real combat, there are so many variables that a tank commander/gunner has no way of knowing what the result of any single shot is going to be. These variables include the actual angle of impact, the air density and temperature. Those are just the obvious ones. Perhaps even more important is the actual properties of the armor and shot at the point of impact. The often under appreciated fact is that steel, like most metals is not completely homogenous and it's properties do vary from place to place in a piece. It's quite possible that a shot may not penetrate in one location , but could if it impacted a inch or two away. These effects can not be modeled in any reasonable game, or for that matter in a computer simulation running on a suoercomputer since the nature of the specific piece of material being shot at is unknowable. I have actually analysed results from penetration tests where the exact same gun fired on targets cut from the the same piece of plate and the actual penetration ranged from complete fracture to penetration of about half an inch.

In game terms you can add as many variables as you like, but you are not going to approach any greater "accuracy"in you results. Far better to only include the variables the commanders (at your chosen scale) could influence. In most cases that's range, ammo choice, stationary vs moving, and maybe targeting location.

You will get greater accuracy. The science is not made up. It is far more accurate to take data from military tests and the science involved then to water things down to such a state that penetration is done to pure chance or based of numbers fabricated or derived with convoluted sachems to "simplify" matters like the scheme used in Panzerblitz for example.

What really baffles me is the extremes in these discussions. It goes from simplifying things to practicably pure chance and then straight into these vastly complicated matters of material strengths etc. There is a happy medium. Regardless of the debates and disagreements with Men like De Marre's equations they still provide greater accuracy then making them up. Shatter gap is still discussed to this day. There are discussions about testing for it. AS mentioned before many rules sets worked fine even when they had to theorize on concepts or technology that was known to exist but classified. Using what is known about shatter gap even if that knowledge is incomplete is easy to model in rules and addresses something that was known to occur at that time.

If you want to model shatter gap I guess one way would be to top off your penetration values at the point where the SG starts and reduce it from there. Where your gun table might look something like this:

Range:.0…….100……400…….600……800….1000..etc.
Pen:…85…….90……105…….100…….95…..90…etc.

But penetration values themselves are subject to variation off the test range and on the battlefield.

A standard test woud be to penetrate armour at the vertical or 30 degrees – good, you get a benchmark figure to compoare gun A with gun B.

But on the batlefield, shots are coming in at all angles, instantly skewing the value of precise penetration figures.

I would agree with those dice rollers who feel that their dice represent many things and would like their dice to take care of shatter gap etc.

You're right. The science is not made up. It also isn't quantifiable enough to allow field results to be completed predictable. Even when controlling every variable possible in lab testing you still get widely varying results due to inherent material variability that defines accurate modelling. The ugly secret about metallurgy is that there are no black and white answers, at least in the real world. That's one of the reasons engineers design things with 3 to 7 times safety margins.

De marres equation , and kruus and oothers have equations for determing penetration. Some disagreemtn on accuracy occurs but they do qunatify things. The reserch into penetration is more accurate then some fabricated rating scale many "simplified" rules use. By using some of this regarfless of the real world realites that its not totaly exact, its still better data. Even with gaps in it it can still be used. No author of wargames rules knows the exact detail of Chobham armor yet its still used in wargames as exanple. There are subtle shades of detail. It doesnt not have to be all or nothing. IT is known that some weapons ammuntion like that of 76mm would break up and close range. Its very simple to add in to a game. Hellcats enagaing a tiger for example at ranges closer then 550 meters will not have an effect. NO need for any more complication then that to model the known shatter gap occuring in with the weapon. The English cam across with soe of there gun in Africa apply the same applicable restriction there. Quantifying penetration is possible using those equations regarldess of the debates about it. Tons of discusion on PC game forums and Tanknet have shown how that math can be put inot no pc and PC games. Nathan Okun made such prgrams that are used by some in Naval wargames. The same can be done with Ground warfare.

All weapons are rated for penetration. And not widely varying results. Guns vs armor website explains that the wide variance has much to do with different test criteria and test material. Its an average yes. But you can determine whether something will penetrate to a good degree. 37MM ATR will NEVER go through A KV-1 no matter what possible variances. That can derived from this without swinging it to the extreme of real world science.

I use Nathan Okun's formula to verify if certain projectiles penetration is within the ballpark. But the results can vary from test data by up to 15%. So no engineering formula is going to match reality to a high degree. I asked Nathan why there was such a high difference and he said no formula can account for all the shock and heat.

The results of program don't vary.I am sure the tests do. But an good average is still much more detailed then some fabricated rating system most "simplified" rules use. Think of Panzerbltiz over 30 years old people still debate attack factors based of some scheme of "simplifying" armor ratings. This science produces good results even if technically just an average. These results can be displayed in a easy to read no math way. So the player only needs to compare penetration value to armor thickness.

Wow – I sure stirred up a spirited debate!

I like the wargames rules I play with to be as 'accurate' as possible within the obvious limitations of playability and knowledge. I asked about rule sets that included shatter gap to see if anyone had come up with a mechanism that did so without impacting too much on playability. (Since the only suggested system was a very detailed RPG style one intended for very small numbers on the board – I guess the answer is no?)

Mitch.

As a closing thought, why do people think its more accurate to add attempt to add factors for every possible physical factor but often ignore the different psychological factors effecting the soldier? Things like lack of sleep, hunger, letters from home, respect for command, etc. These factors are at least as important and probably more so on unit effectiveness.

Nobody was talking about any factor of game but this specific one.. Theres nothing in modeling shatter gap that makes a game unplayable at all. IT's a really a shame that games have to be watered down to yahtzee do avoid extremely simple and easy to ass in details. With the constant about anything being to complicated. Why everybody does go buy a computer game and just kill off whats left this hobby?

I guess the answer is no?

Its actually yes. Mine do, perhaps others as well.

For one example. the m18 Hellcat can not effectively attack Panthers or any other AFV heavier then Panther at ranges of 550 or less. It may not be totally accurate but is a close representation of the effect without detailed math or rules. The game is very playable with this simple easy to remember rule.

For one example. the m18 Hellcat can not effectively attack Panthers or any other AFV heavier then Panther at ranges of 550 or less.

So you are saying we are not going to find any cases where this has happened? Because if we do then something is wrong with your shatter gap rule.

Obviously I have a problem being clear to many people. I apologize for that. In my defense, I usually proofread and read a post back and makes sense to me. But clearly I am not writing well enough for others. Ill keep trying. Sorry.

Maybe breaking down my method would be more clear, I hope.

I search forums for evidence of shatter gap. The one that I found is most mentioned is the 76mm M1A1 gun of the Americans. Its not the only one but Its most prevalently written of so i used that for an example.

Much information shows that shatter gap occurred against heavy German AFV's out to 550 meters. So to simply cover that issue with a quick rule, I note that an attack against those targets at those ranges have no effect.

I look for evidence of it with other guns and apply the same restrictions.

As some mentioned there may have been other weapons shatter gap occurred with. So I also add in the guideline on how to apply the rule to other guns if they find evidence and want to apply the rule to those guns.

That way a basic approximation of shatter gap can be included very easily at the players discretion.

For one example. the m18 Hellcat can not effectively attack Panthers or any other AFV heavier then Panther at ranges of 550 or less.

Ack! Now this is mixing specific data with general classifications. A specific range with some sort of weight class.

Is it any side of a Panther or Tiger or heavy? What if it is the 80mm of a MKIV or the 80mm side of a Tiger?

The heavy slope of the Panther would deflect any 76mm projectile, shatter gap or not. That would be moot.
But a hit by a 3" M7 M62 APC shell at 150 yards on the reverse front slope penetrated.

see you go to far then everbody screams unplayable. So subtle shades.

link

That explains adequately. So to make a comprise as to not arouse screams about playability. a NE for the ranges mentioned where shatter gap effect occurred is enough.

Id love to have the rule apply to armor thickness. I play that way myself but for others Two problems with that.

1. The constant cries about playability. Even though the rule is simple if you explain people say its to complicated.

2. Most everybody I talk to for some reason seems total averted to armor ratings displayed in thickness. To me its the most simple way to do it.

2. Most everybody I talk to for some reason seems total averted to armor ratings displayed in thickness. To me its the most simple way to do it.

I hear ya. If the numbers are higher than their number of fingers they scream "too complicated!".

In firing test No.2 a M10's 76mm gun penetrated the gun mantlet at 200 yds. So shatter gap is not a sure thing.
wargaming.info/ww2/ustest2.htm

In firing test No.2 a M10's 76mm gun penetrated the gun mantlet at 200 yds. So shatter gap is not a sure thing.

Okay, the reason those test don't show the shatter gap was different test materials used by the Americans. The German armor created the effect. That's why I list the targets that the effect occurs with.

I hear ya. If the numbers are higher than their number of fingers they scream "too complicated!".

Yes that's why I often mention many mechanics that are meant to "simplify" as convoluted. It muddies the water. Trying to design a game to cater to this aversion to simple math is very difficult. That's why I wanted to discuss Computer assisted rules in that other forum section. The conversation on that board got bogged down in irrelevant debate though, and has gone nowhere.

"Okay, the reason those test don't show the shatter gap was different test materials used by the Americans. The German armor created the effect. That's why I list the targets that the effect occurs with."

Please explain the factors or characteristic of the German Armor that causes this effect. Shatter Gap refers to the unexpected variation in penetration, not an absolute lack of penetration. Furthermore, your rule would lead to player behavior completely at odds to actual historical practice.

At odds with historical practice? I don't see how that's the case at all. Players employ them as they see fit. Shtter gap was not penetetraion vareince it was a shell breaking up due to hardness differnces.

IT still can occur. Here is something from 1994

link

This is not to detail it down to every pinpoint accuracy. If you do that in these games, Everybody yells complexity, unplayable and all the other common rally words about any sort of detail.

This explains shatter gap sufficiently enough I believe.

Another fact that helped the Tigers a lot was the "shatter gap" effect which affected allied ammunition, a most unusual situation where rounds with too high an impact velocity would sometimes fail even though their penetration capability was (theoretically) more than adequate. This phenomenon plagued the British 2 pounder in the desert, and would have decreased the effectiveness of U.S. 76mm and 3" guns against Tigers, Panthers and other vehicles with armor thickness above 70 mm. It should be noted that the problems with the 76 mm and 3" guns did not necessarily involve the weapons themselves: the noses of US armor-piercing ammunition of the time turned out to be excessively soft. When these projectiles impacted armor which matched or exceeded the projectile diameter at a certain spread of velocities, the projectile would shatter and fail.

Penetrations would occur below this velocity range, since the shell would not shatter, and strikes above this range would propel the shell through the armor whether it shattered or not. When striking a Tiger I driver's plate, for example, this "shatter gap" for a 76mm APCBC M62 shell would cause failures between 50 meters and 900 meters. These ammunition deficiencies proved that Ordnance tests claiming the 76 mm gun could penetrate a Tiger I's upper front hull to 2,000 yards (1,800 meters) were sadly incorrect.

As a general rule, BHN (Brinell Hardness Index) effects, shot shatter, and obliquity effects are related to the ratio between shot diameter and plate thickness. The relationship is complex, but a larger projectile hitting relatively thinner plate will usually have the advantage. There is an optimum BHN level for every shot vs plate confrontation, usually in the 260-300 BHN range for World War Two situations. Below that, the armor is too soft and resists poorly, above that, the armor is too hard and therefore too brittle.

Lots of talk about how field tests produce averages and variance etc. Yet relatively none about the difference between testing and real world use. The tests produce different results then use did in the real world. Not an uncommon phenomenon with weaponry through the ages.

I am not sure in real life if you were in a M18 and you met a Tiger or Panther that you would take the time to optimise you engagement range, assuming you know that Shatter Gap existed, or merely just believed that you had to get close to score a hit on a vital place, which is what I understand most veterans tried doing.

KOing a tank is not about penetration solely, and thats probably the lesser worry. There are many non-penetrating hits that affect AFVs, and crew who are hit don't always kniow what it is, and they bail, or retreat, and then you get penetrations that did not hit a vital area or damage things as they go through.

Given the abstract nature of simulating impact angle, or all the other factors, you are proposing using an additional rule to simulate an exact phenomenom in a sea of inaccurate, abstract, almost surreal sea of mire and mud.

And you think this will make a game better or more accurate?????

G

Supergrover6868

That article on the Tiger mixes two different phenomenon
of shattered projectiles into one. The story on the 2 pdr shattering on German armor is because it was uncapped AP against face-hard armor. This is well known from naval guns vs. ship armor. Basically the hard armor surface breaks the nose of the projectile and the cracks propagate to the rest of the projectile and it breaks up. Capped projectiles were developed to counter the face-hard armor.

The Tiger had the best armor of any tank of WWII. Made from imported Swedish ore and using special and costly manufacturing process. Thus it could resist shells that could penetrate other steel of similar thickness.

There is a shatter gap somewhere out there. But it may not always be at work at definite points. I would break out at least one Yatzee die just in case.

Yes something like a Armored car would not cause the shatter gap. That's why its limited to only the targets that woul'd cause the issue to occur(which are noted in the stats). I used what ever info I could find to incorporate it into rules without the need for dice. Less dive the better for my rules.

Along with guidelines to use the rule in any circumstance a player wants to if they desire. More optional rules I also find better. Point is the original poster wanted to know if they are there. They are in my rules and done simply enough to get the basic jist of shattter gap with s simple and quick rule, even if not 100 percent accurate.

This is all subtle shades. It doesn't have to be all or nothing. There is shades between picking numbers out of thin air and using convoluted schemes of rating to "simplify" and having some simulator address all the real world variables of metallurgy and physics.
Nothing prevents a player for shooting whatever he wants at what ever target. But the effect that shot has will vary by considering the real world results.

Mixing human behavior into it muddies the waters even further. Moral is another section of the rules. They all somewhat connected but for this discussion I am focusing on the AT parts.

If you find a 2001 posting by Lorrin Bird he says the shatter gap for the US 76mm is from 350yds to 1200yds for the Panther gun mantlet.

Yep so a fast and simple is a Frontal turret shot at those ranges against Panther is ineffective. ID like to have a mantlet a separate location, but then you go back to player complaints about complexity. perhaps optional rules with more detailed hit locations

but then you go back to player complaints about complexity. perhaps optional rules with more detailed hit locations

Yeah, I guess.
But, I just would not mix some complicated thing like shatter gap with more streamline rules. I requires things like limit velocity and T/D comparison to work realistically. Now you could work all that out beforehand and just have a small table where the circumstances are listed. If the players are willing to look at another table.

I can't see how you can have realistic armor rules without having separate values for turret and hull. What if the turret turns to the side or rear?

Yep the tables. No matter what, you get complaints if showing ruels to people. Some folks complain about everything. Play testing though worked well. All that was needed for shatter gap was to indicate what targets would cause the effect for the weapon in question(if any) attacks on those targets were ineffective. That covered things sufficiently without needing to introduce the player to mathematics and ballistics.

Hey Supergrover, Last Hussar posted a link to an online calculator that shows the shatter gap for a number of projectiles.
wwiiequipment.com/pencalc

It shows it to be a pretty complicated and elusive zone.