Thread:Vcharng/@comment-1915363-20170829071952/@comment-26574811-20170829083117

About using cm or mm, my guess is that Japan uses cm for their own guns, but if their allies prefer using mm, they will follow.

Bismarck's guns are "38 cm SK/C 34" and Littorio's "cannon da 381/50 ansaldo M1934", so KC followed their owner's way to refer to the caliber, but the French are not their allies.

You know, 38 cm and 380mm are actually different. A 38cm gun can range from 375mm to 384mm, while a 380mm gun can only range from 379.5 mm to 380.4 mm. And when the owner of the gun is your enemy, you can't really be sure.

This issue only exists for countries using metric units. Naval guns usually uses imperial units, so if our enemy is using inches, we can be sure that their guns are either 14, 15 or 16 inches. For metric countries, however, a 15 inch gun may be 380mm (rounded to the closest "clean" metric size) or 381mm (rounded to the closest possible size by millimeters), and when you are not their friend you cannot be sure.

So my guess is that the Japanese (or the German who gathered the intel for them) only knew (before the war) that Richelieu is going to use a "15-inch-class" gun, but was unable to know whether its 380 or 381mm (especially given the fact that its own European allies have mixed up these two calibers themselves), so its probably unwise to be too exact.

However, all these above are nothing better than my guess, this needs to be clarified.

As for the barrel being too close, Japanese wiki did mention this issue in the Wikipedia page for Zara-class, but not in the Richelieu-class. Japanese's own CAs (I think it was Takao-class) also suffered from this trouble (and was fixed by using electronic devices to deliberately separate the firing timing of the two guns by 0.1 second). While this is indeed a very probable reason of why Richelieu's guns did not have accuracy penalty, we should not forget that BB guns have a significantly longer firing cycle than CA guns, and its thus less probable for Richelieu's one half turret to shoot its two guns simultaneously than for a CA to do so.