oh fuck I fucked up my designations, I mixed up the Pak-40 and Pak-36.
However the Pak-40 didn't arrive in large numbers until later into the war, the t-34, meanwhile even in its original form, was immune to 50mm shells from every angle until ate 1941 when thy could be penetrated from behind and the side from VERY close range and with newer anti-armor rounds. The Pak-40 became more common in 1942, but it still lacked the power to take down a KV-1, not to mention that the the T-34's resistance to its shells was practically equal to the T-34s gun range, meaning that to penetrate the T-34 they had to be within range of the T-34's gun.
The T-34's 45mm frontal armor was angled at 60 degrees creating an equivalent of roughly 90 degrees or so of armor thickness
I'll cite you 2 German reports for context on that not being enough:
report from May 1942
"Characteristics of the T34.
The T-34 is faster, more maneuverable, has better cross-country mobility than our Pz.Kpfw.lll and IV. Its armor is stronger. The penetrating ability of its 7.62 cm cannon is superior to our 5 cm KwK. and the 7.5 cm KwK40. The favorable form of sloping all of the armor plates aids in causing the shells to skid off.
Combating the T-34 with the 5 cm KwK tank gun is possible only at short ranges from the flank or rear, where it is important to achieve a hit as perpendicular to the surface as possible. Hits on the turret ring, even with high-explosive shells or machine gun bullets, usually result in jamming the turret. In addition, armor-piercing shells fired at close range that hit the gun mantle result in penetrations and breaking open the weld seams. The T-34 can be penetrated at ranges up to 1000 metres with the 7.5 cm PaK 40 as well as the 7.5 cm Hohlgranate (hollow-charge shells)."
from October 1941:
"For the first time during the campaign in the East, in these battles the absolute superiority of the Russian 26 tons and 52 ton tanksPost too long. Click here to view the full text.