Yuku free message boards

According to the USN empirical formula, which may or may not be precise enough (actually we cannot count on it), Littorios guns are expected to defeat 5.11" of US class B single plate thickness at 30.621 yards

There are no informations regarding the actual penetration power of Littorios guns in cross country tests, so take this with a grain of salt.
The proof angle pointed to by icksydad is not to be understood as breaking angle of the projectile. The penetration through face hardened armour is rather a function and does not end once 30 degrees is reached. Both, guns & shells were to be proofed. A gun or shell type not passing a proofing test was somthing serious, since the proof conditions (a given thickness at a given velocity and obliquity) were usually set close to the limit but they SHOULD be achieved. Of course, Littorios gun may also deafeat a thickness "x" at velocity "y" at 35 or even 45 degrees for that matter since the function does not end here. The curve drops naturally but here, too, nothing definitive about "x" and "y" can be said. The WW2 guntables show a penetration of 11.6" US class A at 41.2 deg obliquity and 1598 fps, implying that Nathan Okun (on whoms Facehd these tables are based on) does not let his assumed penetration curve for Littorio end at 30 degrees. I therefore wouldn´t be surprised to see a penetration in excesss of 12" at 28.000 yards: 1702 fps striking velocity and 41.2 degrees netto obliquity (16 degrees inclination of NC´s belts + 20.2 degrees angle of fall and a reasonable target angle of 20 degrees).
The US had shell proof tests at generally high obliquities, true, but from this one cannot draw conclusions how much the penetration at over 30 degrees is for non US shells - impossible.

What I find interesting on Littorios guns is their very long firing cycle. Wouldn´t 1.3 rpm at best conditions put them on a disadvantage?