"Report on the composition of tables of penetration for 122, 152, and 203 mm concrete piercing shells for A-19, ML-20, and B-4 systems
From April 17th to May 15th, 1941, ANIOP composed theoretical calculations for penetration of 122, 152, and 203 mm shells, and then tested them by shooting at the expected velocities. Work was done according to a program composed by ANIOP and confirmed by Deputy People's Commissar of Defense, Marshall of the Soviet Union, comrade Kulik on December 19th, 1940.
- Processing of experimental data from ANIOP records.
- Performance of trial shooting at 500, 1000, 2000, and 3000 equivalent velocities at plates 30 degrees from normal.
- Processing of data and composition of data tables.
- Processing of experimental data to determine the penetration of 152 mm, 122 mm, 107 mm, and 76 HE shells, and composing penetration tables for HE shells.
Tables for 122 and 152 mm shells were not composed due to a lack of trials material at ANIOP."
Then we have a short section on how the De Marre equation works, which I am sure you are all familiar with. To the practical tests!
"Firing at provided velocities.
Firing the 122 mm corps gun model 1931 (A-19) and 152 mm gun-howitzer model 1937 (ML-20) was done at the 8.5 kilometer position. Firing from the 203 mm howitzer model 1931 was done at the NIMAP main battery. The plates at 8.5 km were hung on metal frames and held on at the corners with bolts. The plate at NIMAP was attached to a large stump using rivets.
Shells used were: stock concrete penetrating 122 mm 2-02819, 152 mm 2-04834, and 203 mm 2-1763, with sulfur charges and blank detonators.
The propellant was reduced, with the following gunpowder types:
- 122 mm gun: NF 17/1 26/39 P
- 152 mm gun-howitzer: 15/7 TsA 18/39 Shuf
- 230 mm howitzer: 17/7 sb.21/40 Shuf
Material on the HE action of 76 and 107 mm shells was taken from ANIOP reports.
Results on shooting concrete piercing shells is attached in table #1. Detailed results are in attachments. Graphs of calculated and experimental penetration are in the attachment. After firing, the shells and plates were photographed, the photographs are in the attachment."
Sadly, I do not have the attachments, nor the next few pages. I do have the conclusions though.
"Summary and Conclusions
Inspection of table #1 and the graphs concludes:
- Results are significantly lower than calculated. Shooting at 500 meters, the penetration is 102 mm with 203 mm concrete piercing shells (calculated: 154), 100 mm from 950 meters with the 122 mm gun (calculated 138 mm) and 90 mm at point blank with the 152 mm gun-howitzer (calculated 132 mm). HE shells penetrate 40 mm (107 mm gun model 1910/30) at point blank and 30 mm at 500 meters with the 76 mm L/40 divisional gun model 1902/30.
- The best penetration was achieved by the 122 mm concrete piercing 2-02819 shells. These shells can penetrate 5-6 mm more than 203 mm shells.
- When penetrating armour, both HE and concrete piercing shells shatter into fragments. The breach in the armour with the caliber of the shell counted as the penetration. In this case, the damage beyond the shell would be dealt by the fragments of the shell and the armour.
- Most experimental data points lie in the vicinity of a 2200 resistance factor armour plate, which is what was used in calculations."