CAMD RF 81-12104-9
Next are the L-11 and F-32 76 mm guns. They can penetrate 40 mm sloped at 30 degrees from 900 meters, but 50 mm sloped at 30 degrees at only 300 meters. This is more or less consistent with the findings in part 2.
Next, we see some unfamiliar faces. The 76 mm model 1902/30, model 1938 (also referred to as a model 1939 in a different part of the document, making it unclear what gun this is), and F-34 guns. They are capable of penetrating 50 mm of sloped armour at 800 meters (quite an improvement over the shorter 76.2 mm guns), or 60 mm at 400 meters.
Here's something brand new. The 76 mm AA gun model 1931 (which was trialed inside a T-34 under the index S-54 in 1943) can penetrate 70 mm of armour sloped at 30 degrees at a distance of 1000 meters.
The 107 mm M-60 gun can penetrate 100 mm of armour at a 30 degree angle at 900 meters (although here it can penetrate that armour at 1000 meters).
The 122 mm model 1938 howitzer (M-30) penetrates 30 mm of sloped armour at 1000 meters. The HE shell breaches the armour, the shell explodes, and strikes the insides of the tank with shell and armour fragments.
The 152 mm model 1938 howitzer (M-10) is tested with three shells. The first is a naval HE (half-AP) shell. It can penetrate 100 mm of "reduced quality" flat armour at 500 meters, or 90 mm of the same armour at 30 degrees. A newly developed AP shell doesn't work so well: at 50 meters, it can only dent an angled 90 mm plate, but is capable of breaching it if it is flat. The resulting penetration is less than a caliber. The old concrete piercing shell can penetrate a 70 mm plate at 500 meters, but only if it is flat. The same plate at 30 degrees cannot be penetrated.
The 122 mm model 1931 gun (A-19) penetrates 100 mm of armour at 30 degrees from 900 meters with a concrete piercing shell.
The 152 mm model 1937 gun-howitzer (ML-20) is also tested with several shells. The naval HE (half-AP) shell penetrates 120 mm of armour at 1800 meters, and 100 mm of armour at 30 degrees from 2000 meters. A new concrete piercing shell penetrates 100 mm of armour at 230 meters. The old AP shell cannot penetrate 90 mm of armour at 500 meters, but could penetrate 80 mm of armour at 30 degrees at 2600 meters (that's not a typo, really, 2600). The shell breaks up and penetrates the plate in pieces.
Now, we get to the big guns. The 152 mm model 1935 Br-2 gun, with a naval HE (half-AP) shell, can penetrate 180 mm cemented armour at 1900 meters, and 152 mm if the plate is angled.
The 203 mm model 1931 howitzer (B-4) can penetrate 102 mm of armour with its light concrete piercing shell (100 kg) at 500 meters, and 27 degrees. The heavy concrete piercing shell (146 kg) can penetrate that same plate at the same angle at 1800 meters. In either case, the shells break up, and penetrate the plate in pieces.
The 280 mm Br-5 mortar, with its 240 kg concrete piercing shell, can only dent 102 mm and 90 mm armour plates at 1700-1800 meters. The rounds shatter into pieces.