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The lower front hull of JPIV and pantherG shows vast different protection in the game


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MikeyD,

Does BFC use a plate quality variable "under the hood" like the one in CMx1? I thought this was a good way to inject real world uncertainty into what might otherwise simply be a deterministic process.

Naval gunnery and armor protection grog Nathan Okun used a similar approach in his game for naval miniatures Battle Stations, with minor adjustments to all ships in, variously, protection, gunnery, projectile terminal performance, speed, damage control and other similar criteria. Again, it helped negate cookie cutter warfare by inducing uncertainty into the overall battle equation.

In both the WW II armor/antiarmor situation and in naval warfare, the players know entirely too much about the military-technical capabilities of the foe and operate accordingly.

Regards,

John Kettler

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Vanir Ausf B,

Please cite a source for the to me astonishing assertion of 10-14% better penetration for CW plugged M61 vs standard U.S. version with burster charge. So far, I haven't found anything to support it in our own John D. Salt's assemblage of WW II antitank weapon penetration data.

http://mr-home.staff.shef.ac.uk/hobbies/ww2pen3.pdf

My dim recollection was that the delta was somewhere around 3%. I suspect the data are in the near mythic World War II Ballistics, by our own Bird and Livingston.

Robert Livingston or anyone owning World War II Ballistics,

If you're still around, would you please check your co-written/your book and let us know what's said in there about the penetration of CW 75mm plugged APC vs standard U.S. M61 APC.

Yes WWII Ballistics is the source for the "astonishing" assertion. However, I miss-remembered one of the numbers. It was 13% rather than 14%, and that was the difference between rounds in which all else was equal. However, in the case of US and British 75mm all else is not equal. The British rounds weigh less but have the same velocity and therefore less energy. When that is accounted for the actual penetration difference is about 8% higher (114mm x .86 = 98mm).

page 58:

The approximate impact of of caps and HE bursters on homogeneous armor penetration may be estimated by comparing the penetration of different rounds. The 37mm solid AP shot penetrates about 94mm at 2900 fps and 0° impact, while solid shot 37mm M51 APCBC penetrates 81mm at the same velocity and projectile weight. The comparison of 37mm rounds suggests that placing caps on the M51 round reduced penetration by 14%.

75mm M61 APCBC-HE penetrates 90mm at 0m and 0°, while 75mm M72 solid shot AP penetrates 114mm, both striking at 2030 fps. If the 75mm AP shot penetration is increased to account for the weight difference the solid shot would penetrate 120mm.

To equal 75mm M61 penetration the solid shot penetration will be reduced due to cap addition and the cavity for the HE burster. If the 75mm M72 AP shot had armor piercing and ballistic caps the 120mm penetration would be reduced by 14% if it followed the 37mm example, resulting in 103mm penetration. To equal 75mm M61 penetration an additional 13% reduction in 75mm AP penetration is required (103mm to 90mm), which would be associated with weakening of the projectile structure due to the HE burster cavity.

When HE cavities weaken the steel structure the armor piercing projectile absorbs energy that would otherwise be used to defeat armor plate, so penetration decreases.

The later section on the DeMarre equation states that methodology assumes a 10% decrease. Page 78:

HE bursters and armor piercing caps reduced penetration by about 10% compared to uncapped solid shot.

I assume they meant 10% each, given the earlier statements. The authors do not attempt to reconcile the different numbers and it is clear that there is a fair amount of uncertainty.

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I just got word from the horse's mouth that Jpz-IV had been intentionally given 'mediocre quality' armor in the game.

This is where I do miss the units stats from CMx1. There is nothing in the game to indicate this so we are left to guess at unexpected results.

But it's good to hear that it is being looked at.

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Vanir Ausf B,

Clearly, I'm not following your logic somewhere in this discussion. There seems to be a logical disconnect, starting with the plugged 75mm projectiles.

For starters, concrete, volume for volume, weighs more than HE filler. Therefore, the plugged ammo projectile must be heavier than the vanilla M61. If plugged ammo MV can be held (not sure whether that was doable) to that of the M61, then the basis for the improved penetration for plugged ammo becomes both apparent and logical. Heavier projectile at same MV = greater KE = better penetration than vanilla M61. Makes sense, but I'm having to rely on your numbers for the delta improvement in penetration.

What doesn't make sense to me is the application of page 58, with its discussion of penetration vs RHA. APC wasn't developed to defeat RHA; it was designed to defeat face hardened armor. As seen by the target armor, the plugged projectile, if hypothetically the same weight and velocity as the stock M61, is functionally identical as an impacting projectile, for it is the same projectile body, but with the burster cavity emptied of explosive and filled with concrete and the fuze replaced with a machined steel plug. Did the plugged projectile weigh the same 14.96 pounds as the M61 APC? I don't know. But as noted, the plugged projectile is heavier and (holding impact velocity constant), therefore penetrates better than the M61 APC.

The above makes sense to me, but the variables cited may not have been correctly portrayed in my analysis. Turning my argument on its head, let's say the plugged projectile is lighter than the M61. If we hold propellant constant, then MV must improve. Therefore, at some undefined closer range, the lighter, faster plugged projectile should outpenetrate the vanilla M61, since V squared is a bigger player in the KE equation than M. But that delta won't hold at some undefined crossover range, for that is where the heavier standard M61 will start to show its reach advantage. Thus, if I'm fighting in the hedgerows, the hypothesized lighter plugged projectile is the way to go. If we move to open country warfare, I'm going to be wishing I had vanilla M61. But the only way to get that is from those Yanks!

Regards,

John Kettler

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Looking back, I should not have wrote that British rounds weighed less. That is too speculative since I do not have the exact weights. Part of the confusion is that I have seen conflicting claims over whether the British used M72 or M61, or both. It seems to me M61 would be more likely since that was what the US was using exclusively during the CMBN time period, but I have not seen a definitive source on this. The bottom line is that all else being equal, removal of the HE charge should improve penetration by 10-13%. The OP stated that he tested both US and British Shermans and saw more penetrations from the British tanks against the highly sloped Jpz IV armor, which suggests that the game assumes the British to be using M61 with a higher penetration than the US version.

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Vanir Ausf B,

If the M72 is the Substitute Standard round, and the pattern is the same for the Sherman as for the 3" ATG and M10, then the M72 will be AP Shot, therefore won't need a plug. The M79 is AP Shot and is the Substitute Standard round for M62A1 Standard APC shell. The Standard Catalogue lists no M72, so I expect it was withdrawn from service before the Catalogue was printed.

Regards,

John Kettler

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This is where I do miss the units stats from CMx1. There is nothing in the game to indicate this so we are left to guess at unexpected results.

Well, not to be too much of a downer on your theory... this same data was in CMBO, CMBB, and CMAK. All three of them have the unit stats that you say would have made a difference. Yet the issue persisted through all three games and two CMx2 games before being spotted.

In fact, the small debate Charles and I had about this is Charles saying "hmmm... either I had a really good reason back in 1999 to make the armor quality lower, or I made a mistake that nobody every caught". The mistake being that he penalized the armor's quality pretty hard compared to other German vehicles of the same timeframe. We went over a few basic facts and concluded that it was a mistake that nobody pointed out and was never corrected until now. Despite being in 5 games we've made over a span of 13 years.

Steve

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Well, not to be too much of a downer on your theory... this same data was in CMBO, CMBB, and CMAK. All three of them have the unit stats that you say would have made a difference. Yet the issue persisted through all three games and two CMx2 games before being spotted.

Yes. And that same data was displayed in the unit stats screen. In fact, I was going to look up what it was it CMBB except the computer I have it installed on died recently. The issue I'm referring to isn't the armor quality being wrong -- I actually have no opinion on that either way -- but the fact we couldn't tell that the results we were seeing were caused by poor armor quality.

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Well, not to be too much of a downer on your theory... this same data was in CMBO, CMBB, and CMAK. All three of them have the unit stats that you say would have made a difference. Yet the issue persisted through all three games and two CMx2 games before being spotted.

Not sure Vomag would have got away with that excuse 70 years ago... :-)

"Vat!?! You've just found you've been making the JgdPzr IV frontal armour from the Kubelwagen cast-offs? Vat is this 'cut-n-paste error' you are talking about? Dummkopf!!!"

*bang*

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The issue I'm referring to isn't the armor quality being wrong -- I actually have no opinion on that either way -- but the fact we couldn't tell that the results we were seeing were caused by poor armor quality.

Does it really matter? The ingame performance is what matters, yes? Yet nobody questioned the performance back when the data was more available. Ironically the performance was questioned without the data. We also responded to the suggestion something was wrong and fixed it within a few days. All without armor stats being made explicitly available to the end user.

Note that I'm not saying it would be a bad thing to have the data displayed somewhere. Because it's been our plan to introduce this at some point since CMSF. What I'm saying is it isn't all that important, as evidenced by what just happened. It's also why we haven't prioritized this over all the other stuff that's made it into the game since 2005.

Steve

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