There is still a lot of misinformation that can be found on the Internet about this topic, with many people still holding the flawed interpretation that the penetration values for soviet tank/AT guns from the official manuals are presenting their performance against face-hardened/cemented armor plate.
I'm posting here these two pages with arguments from the author in favour of installing the 45mm tank gun on the new light tank (T-70) rather than the 37mm one. Of particular note are the penetration figures reported as "theoretical performance of these guns against cemented plate at 20° obliquity".
It can be readily seen that the figures for 45mm ATG are much lower than the ones reported against homogeneous plate, with relative K coefficient higher than the usual 2400.
Soviet AT guns performance vs cemented armor
Re: Soviet AT guns performance vs cemented armor
The effect from having face hardened armour instead of homogeneous on german tanks with 50mm of armour is estimated as follows:
76mm F-34 gun:
50mm RHA/30°: 1100m
50mm RHA/0°: 2000m
50mm face hard/30°: 800m
50mm face hard/0°: 1600m
The effectiveness of FHA against significantly overmatching shells is greatly reduced, but is still superior to that of RHA.
76mm F-34 gun:
50mm RHA/30°: 1100m
50mm RHA/0°: 2000m
50mm face hard/30°: 800m
50mm face hard/0°: 1600m
The effectiveness of FHA against significantly overmatching shells is greatly reduced, but is still superior to that of RHA.
Re: Soviet AT guns performance vs cemented armor
Here's a visual comparison of the performance of this gun against cemented armour and penetration data against RHA taken from here.