ORIGINAL: paullus99
I also saw this in Dunnigan's "Victory at Sea." Don't have the page number right here, but there is also some great information on the AAA armaments of US vs. Japanese ships during the war.
Dunnigan's books may have a lot of info, but they are unreliable sources. There are quite a few mistakes. The lack of a bibliography is also not a good indication of serious work.
If you're seriously going to study Japanese AA, you should read some of the reports of the US Naval Technical Mission to Japan 1945-46. Report O-30 deals specifically with Japanese AA Fire Control. Report O-44 deals with Japanese AA effectiveness. Check the reference section of the website
www.ijn.dreamhost.com for a complete list of the reports of the mission. Any good university library should be able to locate the microfilms of these reports.