The Object 775 prototype tank featured exceptional armour for its time, but how would it fare against the 120mm DM23 Armour Piercing Fin Stabilised Discarding Sabot (APFSDS) of the Leopard 2A1, which entered service more than a decade after the Object 775 was being tested.
Evidently, this isn't a fair real-world pairing, but it's to provide a comparison with the 105mm M1 Abrams video previously, to show how strong the Object 775's armour really was, and to highlight a flaw of early Soviet composite armour arrays -where the rear plate was often too thin to provide structural support under high-energy impacts. Against kinetic projectiles, the thin back plate brings the mass effectiveness of the 90-70-30 array to near 1, whereas if it was something like 60-70-60 (equal thickness and mass), it could be expected to have a mass effectiveness of ~1.15. This was something the Soviets were aware of and their tank armour arrays were changed accordingly.
For reference, based on the Lanz-Odermatt equation, the DM23 projectile (32x360mm WHA) can perforate ~136mm of 300BHN armour at 75°, with the Object 775 having a mass equivalent of 136.5mm RHA. This means the mass effectiveness of the armour is near to 1 (a single steel plate of equal mass would provide similar protection -and wouldnt crack either).
Amazing thumbnail artwork from: @Warthunder
