"Photo #37. Front of "Panther" tank. Direct hit by an AP shell from the 152 mm gun-howitzer. Breach in the armour 360 mm by 470 mm. Shell ricocheted. Distance: 1200 m"
The Panther's upper front plate is no match for the massive 152 mm shell. Despite ricocheting, the armour is breached anyway. Being in a tank that's hit by a shell that big, even if it doesn't penetrate, is no picnic.
"Photo # 38. Turret of "Panther" tank. Direct hit from HE-fragmentation shell from the 152 mm gun-howitzer. Penetration, breach size 350 mm by 370 mm. The explosion of the shell forms breaches in the turret platform and the opposite side. Distance: 1200 m. Angle between the path of the shell and the hull is 60 degrees."
As you can see, HE shells of that caliber are quite effective against tanks, as well as bunkers. In practice, AP shells for the ML-20 were infrequently used, as HE was more versatile.
Next up is the Ferdinand. Not quite a "cat", but still a beast by one of its names (Elefant).
"Photo # 39. Side of the "Ferdinand" assault gun. Penetration of a concrete piercing shell from the 152 mm gun-howitzer. Breach size is 220 mm by 230 mm. Distance: 1000 m."
"Photo #40. Front of the "Ferdinand" assault gun. Direct hit with an armour piercing shell from the 152 mm gun-howitzer. A piece 500 mm by 1000 mm from the front armour plate broke off. Distance: 1200 m."
Even the Ferdinand cannot withstand the firepower of the ML-20! Instead of leaving a hole in the armour, like a normal shell, the 152 mm AP just takes half of the plate with it on its journey into the enemy tank.
Sadly, I do not have any photos of tests against the Tiger, but I do have photos of tests against its successor, the Tiger II. The source is the same test as the D-25's article, CAMD RF 38-11377-129.
"Shot #8. Target: upper front plate. Shell: 152 mm AP. Distance: 100 m.
Result: dent 190 mm by 270 mm, 60 mm deep. On the inside, a bump 10 mm high. Cracks formed, 500 mm and 400 mm in length. The welding seam between the left hull and upper front plate burst."
Seems that 152 mm AP is not as effective as 122 mm AP was. Again, the poor welding seams make an appearance.
"Shot #9. Target: lower front plate. Shell: 152 mm AP. Distance: 100 m.
Result: Penetration. Entrance hole: 260 mm by 175 mm. Exit hole: 85 mm by 160 mm. Narrowest part of the breach is 130 mm by 80 mm. A 320 mm by 190 mm section of armour was blown off on the inside. The break is clean, crystalline. Cracks running all the way through the armour, 300 mm, 280 mm, and 400 mm in length. Left hull weld seam burst on its perimeter. The majority of the shell remains outside the tank."
This is some pretty massive damage. Poor quality armour shows up again, as evidenced by the clean separation of armour pieces. This penetration is amazing enough to deserve a picture in this article.