Is Stuart/Honey gun overmodelled in CMAK?

[SteveP]

What I've read suggests that the British for example were very impressed by the Stuart's speed, maneuverability and durability, but not much by its gun -- generally thinking it as pretty much on a par with their two-pounders. On the other hand, I have read a few accounts which were more impressed by the Stuart's gun in that 1941/early 1942 period. My experience with the Stuarts in CMAK, and also looking at the penetration tables, is that they seem quite able to go toe-to-toe with the Mark III and IV of that era. That is, they don't have to limit themselves to side and rear shots to be effective. Don't know if this is reasonable or not. Of course, there's the standard problem with CM, in that the ranges that tanks fight are so short, which helps the under-gunned machines. Also, the Stuarts are equipped with the different type of AT ammo, and I don't how much that might account for the overmodeling, if that's what it is. Anyway, just thought I'd see if anyone knowledgeable had an opinion.

[MikeyD]

37mm guns stats are all over the place.

There's stats on the German 37mm which is different from the Brit (early war Bofors) 37mm, which is different from the U.S. 37mm tank and towed guns, which is different from the Russian or the Czech 37mm guns!

If BFC did anything, they thoroughly researched the topic (thought I still have a small quibble with the Russian gun). I think a long time ago I compared the game's U.S. Stuart gun penetration numbers to available reference material and it seemed spot-on.

This hasn't been the first game that 'official' numbers have been plugged in and seem to not match the anecdotal evidence. One reason may be that the Allies suffered from a bit of an inferiority complex compared with the Germans, but instead of blaming inferior training they blamed their equipment. In their eyes every gun was an 88, and every tank was a Tiger, the Sherman was hopeless, and the Stuart was always outclassed.

[YankeeDog]

One thing to keep in mind is that the best penetration stats for the US 37mm are with solid AP Shot, rather than Shell. The Allies generally have AP Shot in their 37/2pdr guns right from the start of the war. In contrast, the Germans generally have AP shell for their 37mms, though in 1942 they do get a solid (tungsten) shot option.

In general, solid shot does give you better penetration, at the cost of Behind Armor Effect.

So it may be that the high penetration stats that CMAK gives the US 37mm M6, and the Brit 2pdr, are not contraditory with anecdotes that they these guns were relatively ineffective against contemporary german armor; from a grunt's perspective, it doesn't really matter whether the round if hitting and failing to penetrate, or penetrating and not causing any substantial damage; it's still failing to stop the German tank from shooting back at you!

This is certainly true in CMAK; usually, when firing 37mm shot, you need to get multiple good penetrations to have a reasonably high chance of KO. I've seen even very light armored vehicles like ACs sustain as many as a half dozen side and/or rear hits from Brit 2pdrs, at close range, without serious damage.

Cheers,

YD

[MikeyD]

I'm reminded of a CMBB game I played just a couple days ago. German and Russian tanks slugging away at close range, but what K.O.s my PzIV was an absolutely amazing shot from well over a thousand meters - and through a stand of tall pines - from a measley Russian 45mm anti-tank gun! :mad: One hit and catastropic explosion. The Russian 45mm AP round contained a HE filler. The Russians had literally scaled-up the Rheinmetall 37mm gun to 45mm specifically to field a useful HE charge.

[John D Salt]

Originally posted by SteveP:

What I've read suggests that the British for example were very impressed by the Stuart's speed, maneuverability and durability, but not much by its gun -- generally thinking it as pretty much on a par with their two-pounders. On the other hand, I have read a few accounts which were more impressed by the Stuart's gun in that 1941/early 1942 period.

On the best armour penetration figures I can find for both guns, I would think that the penetrating power of both 37mm and 2-pdr APCBC was about the same. The 37mm looks to be about the same as plain 2-pdr AP at close range, and slightly inferior to AP HV, but because of the ballistic cap it retains velocity and hence penetration better at longer ranges.

Capped shot was not available for the 2-pounder until May or September 1942 (depending which source you believe), and given the disadvantage of uncapped shot against face-hardened plate, this may have made a considerable difference.

All the best,

John.

[John D Salt]

Originally posted by MikeyD:

I'm reminded of a CMBB game I played just a couple days ago. German and Russian tanks slugging away at close range, but what K.O.s my PzIV was an absolutely amazing shot from well over a thousand meters - and through a stand of tall pines - from a measley Russian 45mm anti-tank gun! :mad: One hit and catastropic explosion. The Russian 45mm AP round contained a HE filler. The Russians had literally scaled-up the Rheinmetall 37mm gun to 45mm specifically to field a useful HE charge.

I suspect that CM overstates the difference in behind-armour effect between AP shot and AP shell. The decision not to use APHE in the 2-pounder was a result of firing trials that showed no benefit for the APHE round over AP; and the Russians later filled in the HE cavity in the 45mm BR-240 round to produce the BR-240SP (SP = "Sploshniy", solid) for improved penetration.

All the best,

John.

[SteveP]

Originally posted by YankeeDog:

One thing to keep in mind is that the best penetration stats for the US 37mm are with solid AP Shot, rather than Shell. The Allies generally have AP Shot in their 37/2pdr guns right from the start of the war. In contrast, the Germans generally have AP shell for their 37mms, though in 1942 they do get a solid (tungsten) shot option.

In general, solid shot does give you better penetration, at the cost of Behind Armor Effect.

So it may be that the high penetration stats that CMAK gives the US 37mm M6, and the Brit 2pdr, are not contraditory with anecdotes that they these guns were relatively ineffective against contemporary german armor; from a grunt's perspective, it doesn't really matter whether the round if hitting and failing to penetrate, or penetrating and not causing any substantial damage; it's still failing to stop the German tank from shooting back at you!

This is certainly true in CMAK; usually, when firing 37mm shot, you need to get multiple good penetrations to have a reasonably high chance of KO. I've seen even very light armored vehicles like ACs sustain as many as a half dozen side and/or rear hits from Brit 2pdrs, at close range, without serious damage.

Cheers,

YD

Very interesting insight. However, it doesn't entirely explain that the accounts I've read seem to be concerned with penetration. That is, the tankers seemed to believe they needed to get to the side or rear of the MKIIIs and MKIVs, or at a minimum to within 500-600 yards, to be effective with the Stuart, just as with the 2 pounder tanks. My own experience with the Stuart in, say 1941 N. Africa CMAK, is that the Stuart can fairly readily kill a MKIII or MKIV at much longer ranges from the front. I particularly noticed this first in a scenario (or maybe it was a QB) in which the British had a mix of Crusaders and Stuart/Honeys against a German MKII/MKIII/MKIV mix (Nov 1941, I think). At first, I had the Honeys hanging back, like the Germans did with the MKII, on the grounds that they were both light tanks. Then I discovered that the Stuarts were the most effective tank killers on the map in that particular situation.

[MikeyD]

Well, I guess behind-armor effect only occurs if you can get the shell behind the armor! The Russians and Germans carried on quite the arms race, for every penetration improvement from the Russian came an armor increase from the Germans. I suspect deleting the HE fill from the 45mm had less to do with the inherant effectiveness of a behind-armor explosion than with the rapidly decreasing ability of the 45mm shot to punch through an 80mm Stug hull front.

[JasonC]

We know that HE filler made no difference with small rounds. It may even have hurt BHE slightly. The reason is simple enough, if not intuitive for the shell designers - the energy of the collision is what does practically all the damage. With 37mm to 40mm AP, the kinetic energy of the round is on the order of a million joules. No filler they can carry comes close. Otherwise put, it is the powder that can be fired in the firing tube that is imparting the real destructive force to the target tank, not the much smaller amount of powder that can be laboriously carried all the way to the target before being detonated.

And yes, CMAK overmodels the performance of US 37mm AP. It systematically overmodels small AP compared to large. (Some specific rounds then have it taken back as ammo quality, supposedly - notably the neutered Russian 45mm, which in reality was as effective as either the 2 pdr or the US 37mm). In the real deal, the Brit tankers knew they needed ~500m range to get through 50mm plates. Hits were easy to discern, because they created showers of sparks. Yes multiple hits were frequently necessary or at least delivered (for "death clock" reasons, many of them). But no, they would not have thought they needed close range or a flank if that were the only problem. 37mm AP routinely failed to penetrate 50mm plate at 700-800m ranges. The tankers were not making it up, it was not "really" training etc.

[SteveP]

Thanks Jason. You have confirmed what I could only intuit. Any theories as to why CM over-models small AT guns (which I assume is what you meant ). Not trying to point fingers here, but I noted in a previous post a question about the type of AT ammo that the Stuart/Honey carried. I admit that I've never fully absorbed previous explanations about the different types of ammo, so I am shooting in the dark here. But if this is common, then perhaps it has nothing to do with the type of ammo. Also, are you saying that in CM the Russian 45 is actually less effective than the 2 pounder? That's a hard comparison to make from just playing the game, so that had never occurred to me.

[JasonC]

The penetration numbers are systematically generous to high velocity small calibers and harsh to larger calibers with similar or higher overall energies but larger diameter.

Basically it assumes the problem is to bore through the armor, so the same energy deposited in a narrower area is much more likely to penetrate. While there is some truth in that, total energy matters more, because armor fails in multiple ways and so do rounds.

The guns that come off the worst as a result, are ones that get their energy from mass rather than velocity. That includes the medium velocity 75s and 76s of the US and Russia, and the later large caliber Russian guns compared to smaller caliber, high velocity German ones, of similar total energy.

Some of which is a modeling decision and some of which is "German physics". Standard things like the naval equation of penetration are not nearly so generous to high velocity small calibers.

Other examples of rounds that benefit from this are the 28/20 squeeze bore, the Czech 37mm in 1941 (which kills T-34s through the turret at 600m in CMBB, when in reality it was hopeless against them).

What they did not do is systematically cross check their modeling decisions with tactical realities. Instead they followed their estimating procedure consistently and believed its numbers. The result is things like unkillable StuGs, more readily penetrated IIIJs in the western desert, etc.

But there were some places where the procedure was not followed and instead supposed ammo quality issues were interposed to prevent the logical conclusions from appearing in the game. The leading example is the Russian 45mm after its revision at midwar to many more calibers for the barrel length and much higher velocities as a result. If consistent with the other numbers in the role of energy and diameter, it would outpenetrate the Russian 76mm. Even the earlier one would routinely kill German mediums in 1941 and 1942.

So they gave the Russians crappy ammo and indexed its crappiness to the year. A Russian 45mm bounces from the front of a Panzer II as a result, in 1941. Which is completely wrong, historically. Russian 85mms bounce from StuG fronts in 1943. Etc.

CM armor war modeling considered more variables than any before it and gets most of them right. But then players seeking in game advantages actively search for the places it is off the most, because they create bargains (30+50 front plates e.g.). The result "stresses" the game at its weakest points.

The solution is to avoid constantly taking the same stuff to exploit such bugs, and instead varying the items taken. Brits in the desert should use Crusaders with 2 pdrs, not always Valentines for their armor. Germans in Russia should take Pz IVs with their realistic vulnerability to Russian 76mm from the front, instead of constantly taking StuGs or Tigers. Etc.

[SteveP]

Very interesting analysis. From what you say, I would conclude that the problem is more specifically one of over-weighting shell velocity as a factor in the physics calculations rather than that CM is giving some edge to smaller guns generally (because there are small caliber guns in CM which are as ineffective as they were IRL, AFAIK).

Another aspect to this: from what I've read, the Brits and others were very impressed with the accuracy of the Stuart gun compared to what they were used to. This would be a characteristic of high velocity guns, obviously. The interesting point is that the gunners evidently felt that they had a greater chance of crippling a PZIII or IV (say by aiming at the tracks) as much or more than they had a chance of killing it. Perhaps because CM design focuses to much on penetration, it is also shortchanging the possibility that a gunner might deliberately choose a different objective. Of course, AT fire does immobilize tanks in CM, but I assume this is more a matter of random combat results calculations than anything else.

[JasonC]

No, it is not simply how velocity figures, it is clearly directly related to energy per unit area at impact.

In contemporary modeling, the engineers had precisely the opposite opinion, and thought the T/D ratio - thickness to diameter, meaning whether the armor was thicker than the diameter of the shell or not - was critical to penetration performance, and that larger shells were favored because of it, for equal energies.

The reasons included reduced effect of angle when the shell was as thick as the armor or more, and weaker resistence away from the centerpoint of the impact (armor moves out of the way more readily from the edges of the developing hole).

Here are some examples of what I mean, taking figures for 1941 weapons in Russia and CMBB penetration ratings at point blank range and zero angle.

7.92mm ATR - 1140 m/s, 0.014 kg, energy 9k joules, penetration rating 40mm, J/mm^2 at impact point 45.

28/20 squeeze - 1402 m/s, 0.121 kg, energy 119kJ, rating 87mm, J/m2 95.

37 PAK - 740 m/s, 0.685 kg, 188kJ, rating 41, J/m2 44.

Czech 37 - 750 m/s, 0.815 kg, 229 kJ, rating 53, J/m2 53.

50L42 - 685 m/s, 2.16 kg, 507 kJ, rating 71, J/m2 65.

50L60 - 835 m/s, 2.06 kg, 718 kJ, rating 94, J/m2 91.

88 flak - 773 m/s, 10.3 kg, 3.05 mJ, rating 154, J/m2 125.

Russians -

37mm AA - 880 m/s, 0.665 kg, 258 kJ, rating 40, J/m2 60.

45mm - 757 m/s, 1.43 kg, 410 kJ, rating 37, J/m2 64.

57mm - 990 m/s, 3.16 kg, 1.55 mJ, rating 125, J/m2 152.

76L42 - 680 m/s, 6.3 kg, 1.46 mJ, rating 82, J/m2 80.

85mm AA - 800 m/s, 9.02 kg, 2.89 mJ, rating 100, J/m2 127.

The role of diameter is clearly evident, as is the systematic under performance of the Russian weapons, other than the 76mm. The better ones - 57mm and 85mm - get about 0.8 coefficients, while the small ones - 37mm AA and 45mm - get 0.6 and are effectively neutered as a result.

The Russian 45mm has 80% of the muzzle energy of the German 50L42, but gets only half its rated penetration. It is given less rated penetration than the German 37mm PAK, despite more than twice the muzzle energy and a higher velocity. The Russian 37mm AA is given the same penetration as the German PAK, for a round of the same size and caliber that had 19% more velocity and 37% more energy.

The Russian 85mm had 95% of the energy of the German 88mm but is given only two thirds the rated penetration. The Russian 57mm and the 76mm have basically the same muzzle energy, 1.5 million joules. The 57mm gets 50% higher penetration because the round is smaller and that energy is therefore concentrated in a smaller area.

The role of diameter is clear if you look at the German guns. The 50L60 have comparable penetration to the 28/20 squeeze bore (8% higher) despite 6 times the muzzle energy. The simple explanation is that 1/6th the energy is hitting 1/6.25 the area, since the diameter of the shells is 2.5 to 1 and the area is those 6.25 to 1. Most of the German guns have penetration ratings within the range 0.9 to 1.1 times the Joules per square mm of shell diameter. Even the 50L60 T ammo figure fits this explanation, if one assumes the subcaliber penetrator is approximately .7 the effective radius of AP shot.

There are some rounds that do not fit - the German 75L24, which has equal muzzle energy to a 50L42, has less than half the J/m2, but gets 86% of the rated penetration. And probably deserves it, because total energy is more important and diameter not the unmitigated drawback the basic layout of the ratings pretends.

The neutering of the Russian 45mm is just absurd, though. It might have had trouble with 50mm plate sometimes with angle and range included, but making it bounce from 30mm plates is "German physics". The neutering of the Russian AA guns likewise. The 85mm won't even do what the rating says, failing routinely against 30+50 plates through 1943 - when in reality it was nearly as effective as the German 88mm (only marginally less).

We live with it.

[SteveP]

Originally posted by JasonC:

We live with it.

I've tended to prefer playing primarily infantry or infantry-dominated combined arms (since I think this better fits the scale of the maps in CM). So I haven't been confronted with these anomalies often enough to be sensitive to them before (also, I just happened to be reading accounts of the N. African campaigns while playing CMAK). It was frankly easier to live with when I didn't know any better.

As I understand it, you are saying that the CM physics are out-of-whack in two respects. The first has to do with the relationship of shell diameter, muzzle velocity and the actual energy hitting the armor plate. In this area, you are saying that CM gives the smaller diameter shell disproportionately too much penetrating power -- or the larger shell too little. And, if I understand correctly, you are saying that, with the exception of Russian guns, this bias exists throughout CM. In other words, even the 2 pounder is over-modeled.

The second problem is that the Russian guns are almost all given a degree of "discount" from the standard calculations, in some cases quite large. Do you think this is the result of an extra factor (i.e., representing shell quality) added to the formula -- that is, everyone else is get a 1 for this factor, and the Russians get a .8 or whatever? From the raw numbers alone, it seems that this discount is more arbitrary than that. Any opinions or guesses? Is it only the Russian guns?

The references to "German physics" are a bit unclear. Do you mean that the WWII era German engineers had this misconception of AT physics, or are you talking about some sort of pro-German bias built into the CM modeling of AT physics? If so, it sounds like more of an anti-Russian bias.

[Bigduke6]

If I may jump in, "German physics" is a shorthand term used in these forums by players who believe they have evidence bits and pieces of the CM engine makes German AT weapons more effective than they really were, and Allied AT weapons less effective than they really were.

The distinction is subtle and includes a whole range of variables, among others, like AP effects and the morale algorithms that frequently can make Stalin tanks back away from a face-to-face duel with German medium tanks.

IMO it wasn't a BFI design decision to make the Germans "ueber" that produced the engine the way it was. And no matter the engine's weaknesses, the fact remains that the game engine replicates WW2 tank-to-tank combat on the whole faithfully. It's just like JasonC said; gamers find the holes in computer games and exploit them.

IMO what happened was the designers had an excellent understanding of German weaponry and tactics, a good understanding of Anglo-American weaponry and tactics, and a fair but sometimes flawed understanding of Soviet weapons and tactics, and so detailed and understanding of the physics of AP projectiles attacking steel armor, that the engine tries harder to replicate the physics the engagement, rather than the probable historical result.

As JasonC rightly points out, Soviets are screwed most by the way the engine works. This is sometimes referred to, usually by irate Soviet players after pinging a close-range 76mm round off the side of a Tiger or the front of a Sturmgeschutz, as the "slave nation discount."

Besides, even when it is available raw Soviet data is not always comparable to "western" data. For instance, there is evidence that Soviet scientists used a somewhat more rigorous standard for defining the chance of an AP shell penetration against a given thickness of armor than the Germans did, meaning that that Soviet data plugged into the CM engine effectively made Soviet weapons a bit less powerful relative to the Germans, as the Soviet definition of AP success was - apparently - a bit more stringent than the Germans. Not night and day, but frequently something in the 5-10 per cent range.

Still, in some cases that seems to be enough to skew penetration capacity in the game away from the "real deal", as frequently the difference between penetration and pinging in the game is 5-10 per cent. Almost always, when the margin is close, the German round will penetrate and the Allied round will have trouble.

Another aspect of anti-tank effects that didn't make it into the game, and doubtlessly makes things harder for the Soviets, is that tank armor could degrade after cumulative non-penetrating hits, and generally speaking, the bigger the shell, the faster the degredation.

This was an important part of Soviet AT tactics as, not being clever enough to develop really good AP round in useful quantities, kept up in the armor arms race during the war (and even before) by tying to field relatively large-caliber AP weapons, and trying to defeat German armor not with single-shot kills, but volleys from platoons and even companies or batteries if they could manage it.

The idea was that if you hit a group of armored plates welded together (such as a turret) with enough heavy shells, something would give. How effective this technique was relative to the German approach was any one's guess, but that that was how the Soviets went about fighting German armor from pretty much day one to the end of the war, is a historical fact.

In addition, when the Soviets started fielding super-heavy cannon specifically as heavy panzer bashers, one of the effects they noticed was that if you hit a well-armored German assault gun or tank with a very big AP round (100-122mm), the shock along could cause a disabling hit, even though penetration was not achieved.

There is no chance of this in CM, where either you penetrate and have a chance at a behind-armor effect, or don't penetrate and there is no effect.

As CM also unfortunately does not take cumulative hits into account, the upshot is that a Soviet player has trouble empoying historical Soviet tactics in the game, as sometimes his weapons won't do the historical job. This is not the case all the time, and as noted above the difficulty is most obvious where the game engine is close to a gray area in the penetrate/not penetrate decision.

In my opinion.

[ July 10, 2006, 12:41 PM: Message edited by: Bigduke6 ]

[MikeyD]

"The neutering of the Russian 45mm is just absurd"

I recall at the time BFC was placing a LOT of emphasis on evidence of the manufacture of overly brittle AP shot for pre-43 Russian weapons across the board. This dropped the early war Russian 37mm gun to a laughable state, though the Russian weapon was little more than the Rheinmetall gun with a green paint job. Actually, a large proportion of German 37mm guns after the invasion were from captured Russian stocks - that's why the 37mm gun soldiered on as long as it did!

Still, what can we go by? Combat anecdotes that tend to record the exceptional rather than the usual? Penetration tables that may or may not be extrapolated from a standard formula? Penetration tests which seem to vary wildly from one shot to the next? for every 'perfect' solution you come up with there's going to be someone out there willing to quibble over the results.

[John D Salt]

Originally posted by Bigduke6:

This was an important part of Soviet AT tactics as, not being clever enough to develop really good AP round in useful quantities,

I'm not sure what you mean by "not being clever enough to develop a really good AP round in useful quantities". The Soviets developed HEAT, APCR, and blunt-nosed AP rounds which AFAIK bear comparison with any contemporary design, and AIUI the USSR was not short of tungsten the way Germany was. They didn't develop APCNR or APDS, but neither did anyone else but Britain and Germany (and German APDS didn't use a tungsten-carbide penetrator, so isn't up to much).

I don't think there's anything wrong with the Soviet 57mm, 85mm and 100mm as AP rounds, and the other gun armaments available strike me as sensible choices given the need for HE effect.

All the best,

John.

[SteveP]

Whoops!! Hope I didn't end up trashing my own thread by raising the question of "German physics." I was already aware from other posts that Jason had an abiding concern about the performance of Russian guns in CMBB. I was only interested in whether he detected some system to it.

Originally posted by Bigduke6:

IMO what happened was the designers had an excellent understanding of German weaponry and tactics, a good understanding of Anglo-American weaponry and tactics, and a fair but sometimes flawed understanding of Soviet weapons and tactics, and so detailed and understanding of the physics of AP projectiles attacking steel armor, that the engine tries harder to replicate the physics the engagement, rather than the probable historical result.

I guess the question I'm trying to raise in this thread is in fact about BFI's relative success in replicating the physics. I would not have raised the question, if the problem were one of what happens in a "gray area" situation. I wouldn't have raised it because I wouldn't have known enough to. I raised it because I was observing something in CM that was dramatically out-of-whack with real-life experience. If the Brits could kill PzIIIs from the front with their Honeys at 1000 meters, as they can quite easily in CMAK, then they wouldn't have been risking their lives to get to within 600 meters, or racing around under fire to get a side shot. Jason was basically telling me that, in my ignorance, I hadn't realized this sort of ahistorical result was common in CM with high velocity/small diameter AT guns.

I don't have any interest in complaining about any of this, since I admire these games so much. However, it does seem to me that there is pretty compelling evidence that BFI's attempt to "replicate the physics" could use some fine-tuning. After all, the test of a computer simulation's validity is that the results aren't notably (i.e., more than gray area) out-of-line with real world experience. It's anyone's guess as to whether Steve and Charles are even thinking about this issue for the next version of the engine, since I don't think this has been addressed in any of the relevant posts in the CM2 thread.

[Bigduke6]

John,

The key bit is "really good". My apologies for not being clear.

To try and reduce the muddiness, in my opinion the Soviets absolutely manufactured adequate munitions, and also absolutely they manufactured a lot of it.

However, for a given caliber, in my opinion the Germans managed to get a bit more punch for their shells. When the cannon is comparable - for instance the 76mm used both by the Soviets and the Germans - the German got a bit more AP performance out of the weapon. As I understand it - and guys like John Salt are a lot better at this than me - this is because the Germans were a bit better at AP shell technology. Not factors better, but a bit.

The German approach was, generally speaking, to marry up their marginal to moderate advantage in AP shell quality, to higher velocity cannnon, in order to defeat Soviet armor.

The Soviet approach throughout the war's armour/AP technology race included, in contrast, a conscious effort to field a bigger, fatter, weapon caliber.

My point was that part of the logic behind the decision to go this route, was that the Soviets assumed they would defeating the heaviest German armored vehicles (i.e., the ones we gamers think are cool) not with clinical first shot/first kill, but rather by plastering pazners with multiple hits.

A classic example would be the decision to upgrade T-34 with an 85mm cannon, meaning a turret redesign, time and energy spent adapting an AA gun to tank role, more drain on personnel reserves, and reduced tank output; as opposed to mass producton of the T-34/57, which existed, and was equipped with a weapon specifically designed to defeat armor.

My arguement here is that part of the logic that drove that decision was that if you pound a Panther or a Tiger with a half dozen 85mm hits, from several points of te compass, the chances of producing an armor failure or obtaining disabling damage through cumulative hits are dramatically higher, than if you are attempting the same thing with 57mm.

True 57mm would have been perfectly adequate for a similar mission in (say) early 1942, but of course then the Soviets had oodles of 76mm, so why bother?

I would guess that another factor here is that the Soviets assumed their engagements of German armor would be relatively close, meaning one of the advantages of a lighter shell - that all things equal it is less likely than a heavier shell to lose energy as it flies - would be relatively unimportant to an army whose tankers tried to engage at minimum rather than maximum ranges.

Some one correct me if I'm wrong on the physics for that.

In any case, the Soviet decision went pretty much the same way when deciding whether to equip Stalin tanks with a 100mm or 122mm. When choosing between an existing, bigger gun pretty much at the end of its design life, and a somewhat smaller gun at the beginning of its design life, the Soviets went for the bigger gun. Certainly manufacturing and retooling issues went into the decision as well, but IMO another factor was that the Red Army assumed bigger was better, period.

When faced with a decision on how to get better AP performance, from what I can tell, the Soviets almost invariably went for the bigger gun. My arguement is that a conscious effort to obtain "the hammer effect" on the battlefield was part of what drove the decision, and by that same token the decision was a tacit admission that the route to the best AP performance - that being defined as destroyed German armored vehicles - was not by making the very best AP shell possible.

I'm well aware the Soviets improved their shells over the war, and I'm not trying to say Soviet shells sucked. Just pointing out the Soviet love of size, is all.

SteveP,

It all comes down to what one's definition of "notably out of line" is. In my experience, a CM player's willingness to buy into that proposition increases in direct proportion with the frequency he plays pre-1944 Soviets.

[Michael Emrys]

Originally posted by Bigduke6:

I would guess that another factor here is that the Soviets assumed their engagements of German armor would be relatively close, meaning one of the advantages of a lighter shell - that all things equal it is less likely than a heavier shell to lose energy as it flies - would be relatively unimportant to an army whose tankers tried to engage at minimum rather than maximum ranges.

Some one correct me if I'm wrong on the physics for that.

I think you are, or perhaps have misstated what you meant to say. In fact, the reality of the matter is most often the opposite of what you state above. A heavier projectile in practice will tend to retain more of its initial velocity over any given range. The relationship is not precisely that, of course. The actual relationship is more complex, but given, say, the same muzzle velocity (I know, even that is not usually the case), the relationship is projectile mass divided by aerodymanic drag. For a given material, let's say steel, its mass is proportional to its volume, which in turn is proportional to the cube of its diameter. Many factors determine the aerodynamic properties of a projectile, but the most variable of these in practice tends to be its frontal area, which is proportional to the square of its diameter.

Therefore, as you increase the caliber of a projectile, its mass increases proportionally to the third power and its drag only to the second. You can if you so desire also consider that the larger projectiles usually begin with a lower muzzle velocity and that also reduces drag on them. I hope it is clear from the foregoing (itself a simplification) why small, light projectiles lose a greater percentage of their initial velocity, and thus their energy, over a given range than large, heavy ones. E.g., 16" AP shells still retain a lot of their penetrative power over their full range of something like 20 miles!

Michael

[c3k]

Gents,

I've read this, and have a comment for JasonC .

JasonC, reading your earlier post, quoted, in part, below, you give a table of Joules/square mm for various weapons. I have no reason to doubt any of the muzzle velocities or shell masses you've used. However, I do not get the same values for J/mm2 that you did.

Using the values you list (copied at the end of my message, below), for the 7.92mm ATR I will run through some calculations.

Example: 7.92mm ATR at 1140 m/s, .014kg

Energy = 1/2 * mass * velocity * velocity

1/2 * .014kg * 1140 m/s * 1140 m/s = 9,097.2 Joules.

Okay, that is your listed 9kJ energy figure. That is fine. You list the energy at impact point as being 45 J/mm2.

Using no allowance for projectile shape, but just the area of the projectile leads to using the formula for area of a circle, based on the muzzle diameter, to determine projectile area.

Area = radius * radius * pi

radius = 1/2 diameter

(1/2 * 7.92mm)* (1/2 * 7.92mm)* pi = 49.27 mm2

Dividing energy by area, J/mm2;

9,097 Joules/49.27 mm2 = 184.6 Joules/mm2

Obviously my methodology is different than yours. How did you calculate your "energy/area at impact point"?

Obviously none of this takes into account the shape of the projectile and any effect that the shape and materials characteristics have on penetration. Still, it seems to be useful to get a rough approximation of the energies involved.

JasonC, how did you run your calculations?

Thank you,

Ken

(Edited because Tim Hughes pointed out that I'm a dolt and forgot the correct formula for area of a circle. Thank you. The correction has been applied.)

Originally posted by JasonC:

... Here are some examples of what I mean, taking figures for 1941 weapons in Russia and CMBB penetration ratings at point blank range and zero angle.

7.92mm ATR - 1140 m/s, 0.014 kg, energy 9k joules, penetration rating 40mm, J/mm^2 at impact point 45.

28/20 squeeze - 1402 m/s, 0.121 kg, energy 119kJ, rating 87mm, J/m2 95.

37 PAK - 740 m/s, 0.685 kg, 188kJ, rating 41, J/m2 44.

Czech 37 - 750 m/s, 0.815 kg, 229 kJ, rating 53, J/m2 53.

50L42 - 685 m/s, 2.16 kg, 507 kJ, rating 71, J/m2 65.

50L60 - 835 m/s, 2.06 kg, 718 kJ, rating 94, J/m2 91.

88 flak - 773 m/s, 10.3 kg, 3.05 mJ, rating 154, J/m2 125.

Russians -

37mm AA - 880 m/s, 0.665 kg, 258 kJ, rating 40, J/m2 60.

45mm - 757 m/s, 1.43 kg, 410 kJ, rating 37, J/m2 64.

57mm - 990 m/s, 3.16 kg, 1.55 mJ, rating 125, J/m2 152.

76L42 - 680 m/s, 6.3 kg, 1.46 mJ, rating 82, J/m2 80.

85mm AA - 800 m/s, 9.02 kg, 2.89 mJ, rating 100, J/m2 127.

...

[ July 11, 2006, 09:09 AM: Message edited by: c3k ]

[Bigduke6]

Michael Emrys,

Okay, thanks for that, I stand corrected. Maybe what I am getting at is that all other things being equal it's easier to get a smaller round to a higher velocity, and so increases accuracy at longer ranges. Somehow intuitively it seems to me you if you are betting on shock (as opposed to just penetration) as a way to bash an armored vehicle, the way to go about it is a big caliber weapon fired at as short a range as possible.

That would fit neatly into Soviet doctrine if it were true, but that may be a case of my making the physics adapt to the historical result.

:confused:

[Tim Hughes]

Looks like both sets of calculations are wrong when calculating the J/mm^2.

The X-sectional area is pi*r*r (no factor of .5), but it looks like Jason has calculated pi*d*d (d = 2*r).

So, for the 7.92mm ATR you get

9097/pi*(7.92/2)^2 = 184J/mm^2

And, for, say, the 50L42

507000/pi*25^2 = 258J/mm^2

(Of course, there could be a factor of 4 allowance for the fact that the projectile has slowed down by a factor of 2 travelling from the muzzle to the target.)

In any case, the exact numbers don't matter. Since the factor of 4 is linear, comparisons are valid with either set of figures.

[c3k]

Tim Hughes,

D'OH! That's what I get for being pedantic! I decided to put in all the 1/2's for the diameter to radius conversion and I got carried away.

I'll edit my post to reflect your correction.

Thank you!

Regards,

Ken

[SteveP]

BigDuke: the charge of being "notably out of line" can indeed be a consequence of whose ox is getting gored. However ...

This thread has now somewhat bifurcated into two topics. The topic that I launched had to do with the over-modeling of the Stuart/Honey gun. Inasmuch as my interest in these games is historical simulation, it requires the constant exercise of self-discipline not to be too anal retentive about historical "accuracy" in the simulation. From that perspective, if I found in playing CMAK that Honey's were killing PzIIIGs at 600-700m, while IRL Brit tankers wouldn't bother shooting until they got at least under 600m, I would decide that this discrepancy is hardly worth consideration, even if I thought I knew where the "error" lay. However, in CMAK those PzIII commanders had better start worrying when they see Stuarts getting to with 1200m of them, while they can safely ignore the Cruisers at the same range. To me, that's not only out-of-whack historically, but it's disturbing because the discrepancy is radically affecting decision-making in a CMAK battle.

Now, if anyone thinks the Stuart's performance in CMAK is not notably out of line, and/or not an indicator of a more than trivial problem in the CM physics model (sorry for the double negatives), then any comments along that line would certainly be consistent with the basic theme of this thread.

The other topic which has arisen in this thread is the putative under-modeling of Russian guns in CMBB. This started, obviously, because Jason -- in the course of explaining why he thought all or virtually all high velocity/small caliber guns were over-modelled in CM -- decided to point out what he thought was a notable exception to this rule. There's nothing wrong with that, per se, although I for one had to study his analysis for awhile to parse what he saying about how CM treated small caliber vs large caliber, from what he was saying about the overall treatment of Russian guns vs German guns. Since I play CMBB from time to time, I do find this second topic interesting. Is the performance of Russian guns notably out-of-line in CM? I don't know. I guess I'd ask the question this way: if German tankers IRL regarded the Russian 45mm as being about as dangerous as the Brit 2 pounder, then I would say CM has it close enough. If, on the other hand, German tankers regarded the 45mm as a threat at least as great as German players in CMAK should regard the Stuart, then I think CM has it wrong.

How's that for keeping it simple?