Given that the Leclerc ended up with lower shooting scores in all trials and competitions, I seriously doubt that there are issues with firing on the move. At the maximum speed that the Leopard 2 realistically reaches off-road, it can accurately hit its targets. Driving along flat roads with higher speeds shouldn't negatively affect its accuracy.
I guess you are mixing something up with the Leopard 1, which could not accurately fire on the move at speeds higher than 20-25 km/h...
The there were tungsten and DU versions of the XM827 during development, but the DU version was prefered in the end (still canceled in favor for the M829 though). Likewise the US Army tested WHA and DU versions of the XM833. The article from the ARMOR magazine doesn't mention any materials, but it also includes one mention of the M735A1 (with DU penetrator).
At the time, DU alloys could probably achieve better performance, but the 120 mm DM13 should be better than the M735 APFSDS and its M735A1 sub-variant, simply based on physics.
It is availabe on the website of the German patent office, the European patent office, Google patents and many more
Actually it seems that modern tungsten heavy alloy penetrators are usually made with a slightly smaller tungsten content, in some cases as low as 90%. This way it is possible to create alloys with more ductility and/or strength.
The data used by Warthunder for the M735 is simply wrong. It is not possible for the M735 to penetrate the same amount of armor as the DM13 APFSDS at the same distance, given that penetrator length is essentially identical (~313 mm vs 315 mm), but the muzzle velocity and length-to-diameter ratio are in favor of the 120 mm DM13. An older article published in 1982 in the US ARMOR magazine suggests that the XM827 (German 120 mm DM13) has a 20% larger penetrator mass and was able to defeat all targets during the 1976 gun trials by NATO at longer ranges than the M735 (the M735 failed to penetrate some targets).
Given the higher drag of the DM13, the M735 might be able to reach the same level of armor penetration at ranges greater than 4 kilometres (assuming deceleration stays constant up to this distances), but the 105 mm rifled guns M68 & L7 weren't considered accurate enough (neither was the 120 mm Rh 120 L/44 firing 120 mm DM13 ammunition).
The layout of 120 mm DM13 is identical to a patented design from 1972.
Patent drawing from patent DE2234219, registered on 12th July 1972. They certainly couldn't take design aspects from other APFSDS ammunition which didn't exist at the time.
AFAIK the table posted earlier was made by another internet user, who based it on a (de)classified report. He might have made some error when entering the numbers from the paper into the computer, because the DM13's penetrator diamter is listed as larger than the actual diameter of the sub-projectile, which is physically impossible. The penetrator diameters for the L15 APDS, the L52 APDS and the 110 mm APDS are all smaller than the projectile diameter - just as expected.
The weirdly shaped ballistic cap is in fact a windshield and a very normal design. Several other APFSDS rounds from NATO and the Soviet Union (among them the L23A1 APFSDS, Lekalo and Mango) use the same method to connect the windshield to the penetrator.
The penetrator design and working mechanism is not similar to the Soviet 3BM-15 APFSDS and its sucessors. The Soviets used very brittle tungsten-carbide cores, which were shaped like bullets and embedded into the steel, because they would break otherwise.
The tungsten-carbide tips would break off when hitting sloped armor or become damaged when penetrating spaced armor, which significantly reduced the performance of Soviet APFSDS. That is why the tungsten-carbide core was later moved to the rear of the penetator to deal better with spaced and composite armor arrays.
3BM-26, the tungsten-carbide penetrator is located in the fin-section.
The DM13 APFSDS uses a penetrator made of WHA; the patent from 1972 suggests that 95% tungsten, 3.4% nickel and 1.6% iron would be desirable. The steel sheat is only added, because of the low yield strength of the WHA, which breaks apart when hitting (highly) sloped armor. The steel sheat apparently doesn't extend over the frontal (separate) section of the penetrator, because the tip always breaks off when impact sloped targets. Furthermore this layout was found to be advantageous against multi-plate armor arrays, as the larger frontal portion would result in a larger hole, through which the main part of the penetrator could travel without being damaged.
Yes, from what I know that's true, but the values don't match the ones I've been able to find:
And it's more than just sheathed, it's also segmented with a weirdly designed ballistic cap and the first actual "penetrator" part seems to be similar in function to the ones found in 3BM15 etc (though substantially larger and with a tip reminiscent of L23A1).