Because of it’s blunter nose the T50E1 would likely overperform the german counterpart against high obliquity armour. :p
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PzGr 39/43 had an army limit of 3322 against 3-3/8” 241-263 plate at 55 degrees.
T50 had an army limit of 2811 to 3251 against a similar plate. They used different lots of the T50 so I’m guessing they were development rounds.
I mean, I think you should take this result with a grain of salt.
3322fps is almost muzzle velocity for that gun. And do you actually believe that 100mm of cast armour at 60° on an JS-2 is weaker than 86mm/55° RHA?
You should check this 200 post thread on this topic when you have the time: 8,8 cm PzGr 39 Performance - Axis History Forum
That’s fair. Just trying to compare data using the same standard.
Finally, after a long and difficult fight with bad quality scans and clunky user interface of 3D modelling software, I arrived at solution.
Spoiler
The cap + ws take up almost exactly 22% of total mass of the shell. Hurrah!
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Good to know for sure it’s 22%.
What software do you use?
I’m ashamed to say.
It’s
Spoiler
FreeCAD. :D
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No shame in using what you have.
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Meh, I use the free version of Fusion 360 :D…
On another note…
I believe I may have figure out part of the issue with the 90mm M82 filler controversy… Which may also be the reason why there are two different values 0.31lbs or 0.44lbs depending on the manual, even during the same time period.
The explosive filler used in US APHE shells, Explosive D (Dunnite, Ammonium Picrate), can only be press loaded. However, it can be press loaded to 5 different densities, ranging from 1.41g/cc to 1.64g/cc.
Spoiler
Standard loading Density spec for Exp. D in US AP shells is ~1.48g/cc…
However, I haven’t had the time to make a 3D model of the M82 Shell yet. So I haven’t had the ability to play around with the filler density to see how it would effect the filler mass. But, just from playing around with a cylinder mass calculator, there only seems to be a difference of about 16-17grams when changing from 1.48 to 1.64g/cc with a cylinder of approximately the same volume as the M82 burst cavity.
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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 🤔