I don't have any values, sorry. But I'm still confused with some things. Zaloga wrote [in his comparision between M1 and Iraqi T-72s) that the M829A1 will only penetrate 57 cm @ 2 km (instead of typical estimates between 60 and 70 cm). If that is true, nothing would speak against 56 cm for the DM 43, imo.
120 DM13 is an unique round, it is the only German APFSDS developed prior the 105 mm DM23 APFSDS with technology from Israel was made (i..e licence procduction of M111 Hetz). But it might incorporate technology from the US shared during MBT-70 development.
Stefan Kotsch wrote on his homepage that it would penetrate 230 mm RHA at 2,2 km - this statment is total bullshit. He must have forgotten some angle, as the typical penetration of 105 mm APDS with WC core was about 250 mm at 2 km. The early 115 mm APFSDS with steel penetrator could penetrate 270 mm RHA at 2 km, while the 120 mm APDS L15 from the L11 gun (with a L/D-ratio of only 6 - 7!) is claimed to penetrate 355 mm RHA at 1 km.
The sub-projectile of the 120 mm DM13 has reportedly a diameter of ~38 mm at the thickest part. If we measure the L/D-ratio by using this diameter and measuring the projectile from tip to end of the fins, it should have a L/D-ratio of ~12.4. But if we use the diameter of the tungsten penetrator (which is below that of the steel-jacket) and do not include the fins, the L/D-ratio will be ~14 - 15. The steel-jacket is an unique feature of the DM13, as it does not cover the whole penetrator, only 3/4, while the front (where the penetration should start) is uncovered. Jane's wrote in their text about the M829 that the XM827 (the US licenced version of the DM13) would not use a two-piece penetrator while the DM13 would - unlucky I don't know wether the "two-piece" refers to the steel-jacket or means that the tungsten penetrator consisted of two smaller ones.
Rolf Hilmes featured in one of his books a comparision between the Leopard 2 (so called 2A0, first batch) and the T-72A, both tanks entered service in 1979/80. Regarding firepower he wrote, that the 120 mm L/44 gun at 540 MPa and the 125 mm L/52 gun at 450 MPa would both release ~10 MJ of muzzle energy.
I would assume that the DM13 penetrated more than the 120 mm L15 APDS from the L11 tank gun, as the joint comparision of the US 105 mm, British 110 mm (being roughly as strong as the L11) and the German 120 mm gun showed that the Rh 120 L/44 did have the best firepower. With estimations I would be rather carefull, but as minimal penetration (or as lower bound estimate) 360 mm at 2 km seems already a little bit low, then the 120 mm APDS would be stronger at 1000 m (or Jane's claimed a too high penetration value, happens sometimes). The 450 mm at 1 km could refer to the DM13, but they could also be achieved using another round. I think that the German army wanted to have a tank round capable of knocking out the T-72 (being the best armoured Soviet tank against KE when the Leopard 2 was developed) at least at 1 km. The CIA believed that the maximum armour thickness of the T-72 turret was 45 cm cast steel, but as the Germans did already some cooperation with Isreal prior buying the M111 (they once imported a captured T-62 from Isreal to compare it with the Leopard 1), it seems possible that the Leopard 2 engineers and the people working at Rheinmetall got quite detailed information at what to penetrate. Kotsch value of 23 cm is very low, but let's assume he forgot an angle... if it would be 60°, the armour penetration would be twice as much... 46 cm (but at more than twice the range) -> doesn't really fit. I believe that the DM13 was at least very close to 38-40 cm at 2 km, which should be close to 45 cm at 1 km. In the end it got a better L/D-ratio (based on penetrator only) and a higher muzzle velocity than the M735/M111, which both penetrate ~35 cm at 2 km.
DM23 has an even smaller diameter and a longer penetrator. It will be better than DM13, how much is questionable.
Regarding DM33/Polish APFSDS replacement:
If DM33 would fail to penetrate 50 cm, why would the government not go and buy modern French/German/Israeli/US ammo - all these countries have at least 2 rounds developed after DM33, which could in theory penetrate more (not sure about first Isreali 120 mm APFSDS) than the wanted 50 cm. I think the government just wants to help it's own defence industry. Don't get me wrong, I don't want to claim that the Polish tests were faked, but a failing forgein rounds is a nice reason for buying homemade ones.
