The absence of that extra 0.5" is pretty noticeable in the drawing however.
In fact, a lot of the gun mantlet armor (not just US) is declared as being thicker than is physically possible.
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I just did pixel measurements of the 1st image you provided.
The thickness came out to 3 inches, assuming the rear is 2 inches.
Keep in mind that since these blueprints are basically cut down the middle of the turret, a tiny bit of the front is cut out to fit the gun shield/rotor shield mount. So I’ve counted the entire thickness including the mounting for the gun shield.
Compare the thickness to the glacis, and remember the rear is given as 1.75" in the real fire trials.
I found it was 51mm glacis and ~63.5mm turret.
About 16.64 px for 50.8mm and ~20px for turret face near gun.
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Sure, will do.
Also, to point out, this is not mantlet armor.
Yes it’s another error, I think the mantlet of M34A1 mount is actually 30.5mm, which matches its physical thickness. 50.8mm would require it to be about 66% thicker than is actually modelled
I got 15 pixels for the hull front, 20 pixels for turret front and 13 pixels for turret rear.
Assuming 2 inches on the hull front (50.8 mm) that means 2.667 inches on turret front (67.7 mm) and 1.73 inches on turret rear (44 mm).
I wonder what causes this discrepancy. Could it be an early Sherman thing where later Shermans have thicker armor?
I’m not disagreeing, I’m simply pointing out that these turret armor values are unrelated to the mantlet.
In fact I don’t remember ever seeing official thickness values for the M34 mantlet.
I found the turret face is closer to 18 pixels, maybe 19 pixels myself. So we can assume it’s 63.5-67.7 at maximum, with significant taper.
The drawings though are 1941, 1942
It’s consistent with results from tests at the end of the North African Campaign, so like May 1943, so whatever turret with this “76.2” at 30 face would need some investigation, if it even exists, since you would need to redo the gun mount installation.
In general there are a lot of historical inaccuracies helping US tanks right now, like the real Pershing mantlet seems to be somewhere around 3" according to US live fire testing (pennable at something like 6,000 yards by its own gun) but is 4.5". But that’s thicker than its own blueprint by a lot so
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guh
Let’s try to find the possible change in thickness, with the positive bias (it exists)
I’m thinking it’s not a D50 series but D7
I know it tapers down at the top and bottom.
3 inches seems far too little though. Do you have any blueprints for the M26?
Just added pictures, limit of protection of gun shield is 5000 yards so 3.5" maybe 4"
In terms of shape it’s close to the M36 Jackson mantlet
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But “protection” is a different thing from actual perforation of the plate.
In other words, it doesn’t mean that the round physically goes through the plate, and they specify “protection ballistic limit” on the document.
One thing to take into account is that the M26 has an extra plate behind the main gun shield. It is completely possible that they took the lower “protection” of the gun shield into account and so added the extra plate to catch shrapnel. (image show T99 gun mount, M26 uses the T99E1, which is the same but supposedly up-armored)
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Yes so you can adjust the striking velocity down.
So when using real demarre (and not gaijin) I get ~93mm with K1950 (which is an extremely optimistic value)
Mistake this is all for 526 m/s
If I use K2100 it’s 83mm
Looks like the writers of Ballistics armor and gunnery were off by a bit when assuming it was just 76mm equivalent
For raised velocity (pass through 1.06x), I get ~91mm with K2100, 101mm with 1950.
Looking at the blueprint that’s like 3.5" or more (my measure)
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AD0301343, “An Analytical Study of Data on Armor Penetration by Tank-Fired Kinetic Energy Projectiles”, contains multiple tables that state army criterion ballistic limits for dozens upons dozens of different rounds.
This is what it states for 90 mm M82. The 3rd column is the angle, 4th column is thickness, 5th is BHN, 6th is feet per second.
So with army ballistic limit (which is, if I’m not mistaken, simply that there is a hole you can shine light through), you get ballistic limits anywhere from 1713 to 2030 ft/s for 4 inches depending on hardness, which matches what you stated with multiplying velocity by 1.06. Army limit is still not as stringent as something like navy limit which is basically what is used in WarThunder.
Unfortunately the ft/s value of the 3.5 inch plate has a completely unreadable digit.
Ah for 505 m/s (I used wrong velocity)
79 - 89
And 505x1.06
85 - 95
I used +21 m/s velocity as a mistaken unit conversion
It’s 1652 ft/s which is decidedly less than the lowest value on the 4" group
Yes, however different criterions.
The document you showed explicitly is talking about protection criterion. This one is army criterion which, if I’m not mistaken, leads to higher velocities.
Yes I adjusted striking velocity x1.06 which is often enough for a pass through from army limit.
It’s technically 503.5 but I don’t wanna do the math again
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And I pointed out that if you do that adjustment of x1.06, from 1652 ft/s you get 1751, which fits directly on the 4 inch group.