Development of the Imperial Japanese Navy Battle Cruiser (Part 5)

The 'Nachi' class defect was the accuracy of the main guns.
System of bombardment from 1910 to the end of World War II was probability shooting system .

All the main guns volley. and all shells fall on a sea surface and the range to which a shell falls on a sea surface is called 'pattern'.
(In the imperial navy, it was called the spraying range of the shell.)
Spraying range of the main guns of a battleship is 200 to 300m pattern.
If it catches and shoots at an enemy ship at the centre of this pattern, a hit will surely be obtained.

In 'Myokoh' class, this pattern was the range of 430m diameter.
An enemy's large vessel is about 200m hit will not be obtained if there is a pattern no less than 200m.
In the 'Aoba' class of loading of the same 20cm gun as 'Myokoh', a pattern is small..
Hence, the rate of a hit of 'Aoba' has obtained 6 to 16%.

'Nachi' class was not able to obtain 7% or more of rate of a hit.

When 'Aoba' class shoots 10 times, the number of shells is 60, and a hit shell will become 9.6 if the rate of a hit is 16%.

But in 'Nachi' class, when it shoots 10 times, the number of shells is 100.

(However, a hit shell is 7.

It became a big problem in the navy.