I have a full 3D solid model of the M82 I made in Solidworks. I can send you the file.
There is no need to build a 3D model for that. Mass is linearly proportional to density, so a loading of 1.41g/cc will have mass 86% that of 1.64g/cc.
86% of 0.44lb. equals to 0.378lb.
Not enough to explain the 0.31lb value.
Edit:
WIP
I think I posted it before but here are the two versions of 90mm M82:
90mm M82 are the third and fourth from the left
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On the topic of realistic performance of the US shells with rounded rose, like the M82.
Intuitively we know that their performance against thick armour must be a bit lower than that of the shells with a more pointy nose, but how much exactly?
Well, I decided to find out.
First, let’s compare the results we can obtain using the NPL formula with US data on uncapped AP with sharp tip:
As you can see, the match is almost perfect, so we can safely conclude that the armour quality and penetration criteria used by the US specialists will not influence our results.
Then, lets compare the NPL estimates for a 14.7lb. M62 APC shell tested here. This smaller weight (vs 15.44lb for a combat projectile) indicates that the shell is modified by removing it’s windshield (-0.40lb) and replacing the fuze with a steel plug (-0.35lb.) as well as replacing the explosive filler with the same mass of inert material (+0 lb.)
Spoiler
If we apply only the adjustment for AP cap (+2% to BL) we are still short of what we see here. In order to see just by how much we interpolate the data and calculate the ratio between the experimental and estimated values:
As you can see, the average experimental values are ~3.6% higher. This is after we apply the adjustment for AP cap, so the total BL coefficient to use with NPL formula when estimating the penetration of the US APC shells with round tips is x1.02 * x1.036 = x1.056
The results we get from NPL formula with and without this new adjustment:
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So why the decision on the rather round noses?
Intuitively, I would say maybe to get better effect against FHA, even in cases the cap got removed due to spaced armor.
Or in which other scenario would the round nose improve the performance? Against 30° armor?
Against sloped armour, a shorter nose is better, yes, but also one with a sharp edge that bites into the armour. A round one like this would just slide off.
If a rounded nose would’ve prevented the FHA from having a detrimental effect on the shell, why then also have an AP cap? Clearly the americans thought that both were required.
Looks like in this test the 50mm FHA was perforated by the de-capped 75mm M61 shell at a lower velocity than should be expected if it’s nose shattered.
I can’t perform a more detailed analysis until I get to my PC.
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The M61 without explosive filler penetrated the spaced armor array? 🤔
20mm Homo and 50mm FH plate sounds a lot like a Pz III L/M.
For whatever reason, production 76mm M62 had especially bad heat treatment. I wonder if the other APC rounds had similar issues. Maybe the lack of proper heat treatment made them use the large cap and round nose to make up for poor metallurgy.
Nah, I think you’re way off.
Look at this, at the outbreak of the war the US APC shells had a pointed tip:
The 37mm was a high velocity gun, and these worked well enough with it.
This design was changed only with the introduction of the 75mm M61, after they encountered trouble with German tanks equipped with FHA in North Africa.
I immagine when the firms first began manufacturing 75mm M61 APC shells, many of them had heat treatment flaws, but with the US M3 75mm gun firing them at relatively low velocity, both good and bad quality shells performed pretty much the same.
After the introduction into service of the high velocity 76mm gun, they were asked to make APC shells for it as well and that’s were they started to encounter serious problems with producing consistently good quality product.
Im not sure if these problems have been fully overcome by the time the 90mm entered service.
@Conraire might have something to add on this topic.
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@KillaKiwi I got to my PC.
The estimated BL for this shell against 50mm/20-30° of RHA is 1300-1400 fps. With a shattered nose, 1700-1750fps. Clearly once the cap has been stripped, the rounded nose didn’t help it prevent shatter any more than a normal one.
Edit: It’s still pretty effective when fired at 2030fps. Only when fired from the L/30 75mm US gun the screened Pz.III stands a chance to survive a hit at normal combat ranges. The penetration distances for reliable pen against the shielded driver’s plate or turret front are 450/800m at 30/0° angle respectively.
But the velocity difference between the M2 and M3 wasn’t that great 🤔
It didn’t really get solved until post war for tank AP rounds. Then they started using the same method of hardening that was used for naval shells. Which I think is called Sheath hardening?
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I don’t know what to say. Those are just ranges at which the M61 shell slows down to 1600-1700fps if fired at 1850fps. You can check the graph for this shell in TBv3 for the 75mm M3 gun. Take the distance where the shell slowes down to 1850fps as the new 0yards distance point and see for yourself.
@Conraire bzzzt wrong. It’s the other way around. At first, the US Army was using Sheath Hardening for their ap shells, adopted from Naval shells, then eventually examined the captured German ap shells and realized that their decrementall hardening pattern is superior for conditions encountered by tank guns.
More reading on this topic:
https://forum.axishistory.com/viewtopic.php?p=2333502#p2333502
https://forum.axishistory.com/viewtopic.php?p=2462863#p2462863
https://forum.axishistory.com/viewtopic.php?p=2297063#p2297063
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The picture you posted is the failed production heat treatment. Here is the intended heat treatment from prototype rounds.
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Thanks, I know this by now. Conraire showed me.
Those my posts on AHF are several years old. I have learned a lot since then.
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Yeah, he’s a good source of information.
sir? do you play the tigers at all, i fucking love them and they are in no way bad, neither is the german 3.0, 3.7, 5.3, 5.7, 6.0, 6.3, 6.7. I know this as i play all of these brs for fun when ive had a little too much of the bullshit of top tier. So dont go flining wild statements like all of germany 1.0-8.0 is trash, specify as they do have some dog vehicles but they also have fucking amazing ones as well.
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It’s been a year since this topic was created and we still don’t have an answer as to why Soviet and German tanks get multiple variants of their APHE rounds, but not US tanks. Why can’t we even have the discussion? @Smin1080p_WT
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I think that creating a suggestion to implement two separate M82 shells would be the best method.
I’d do it myself but I don’t feel like learning and doing resarch about them all over again… its been a year since anything happened here.
So if anyone has the time and is up to date with the info, you know what to do :)
I bet it will gain some traction this way
It won’t. I’ve created many suggestions, bug reports and threads. The Gaijin ground devs just have different standards for what they add to US vehicles vs what they add to other vehicles.
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