I mean, check on this site Italy 381 mm/50 (15") Model 1934 - NavWeaps
The penetration of 381 mm/50 (15") Model 1934 at 0 distance is 814mm instead of 870mm. The current value in-game is even higher than that of the Yamato’s Type 94, which does not make sense as all
In 2019, the armor penetration system in War Thunder was moved from a documentary basis (where the configuration of penetration was based on data from documents and firing data for each weapon and ammunition type), to a calculation basis using the Jacob DeMarr and Lanz-Odermatt formulas. Nowadays documents are only used to determine the attributes of the shell (calibre, mass, velocity, explosive mass, shell type), while the actual penetration in-game is purely based on calculations.
OK, thanks for letting me know. In this case the penetraion problem is not with Rome, but with other battleships, I will do calculations and report problems in a different thread