I’ve ran into a few sources saying it’s 25mm
Another players had found that the AP model is too early for the A-IX-2 powder and it should be using normal TNT filler. So its filler should be reduced to 25.7kg. Large but not ridiculous.
Though someone really needs to look at her armored scheme and that ridiculous armored section on her bow. Its a nonsensical feature more useful to War Thunder Naval damage models than irl applications and highly suspicious. Just having it removed would do wonders in making her less invincible.
Final note is to move most of her crew to her machinery spaces because them hiding in her most armored sections in the magazines is bullshit. That, she’ll be more vulnerable to crew death.
Actually it would be more useful in real life as Gaijin doesn’t implement shell getting slower when hitting armor.
Her current crew in dev server is about 100 less than what is projected, so maybe not big help?
I would rather suggest Soyuz in 9.3, Iowa in 9.0 so all new battleships would only fight themselves.