1) IS is my abbreviation for the incendiary shrapnel round (sankaidan) intended for AA use.  These were officially listed as Common shells, but were actually incendiary fragmentation rounds.

2) The propellant charge was in one bag with a 1.75 oz (50 gm) black powder igniter.

3) Fuzes were set by hand on the loading tray.

4) "New Type Projectile" is the designation used in the US Naval Technical Mission to Japan report O-19.  This projectile was under development at the end of the war and does not appear to have entered service use.  This projectile was boat-tailed, more streamlined at 13crh, had a maximum surface range of 25,180 yards (23,025 m) and a maximum AA Ceiling of 49,260 feet (15,010 m) at 90 degrees elevation.

5) The flat-nosed ASW projectile was issued in 1943 following extensive testing.  This is listed in US Naval Technical Mission to Japan report O-19 as being able to penetrate a 9.85 in (25 cm) plate of Ducol Steel (roughly equivalent to USN HTS) at a depth of 26 feet (8 meters).  However, based upon other errors in this document, I would believe this to be an error in metric to english unit conversion and that the actual performance would more likely be 0.985 in (2.5 cm).  Range for this performance is not given.

6) Illumination rounds were rated at 680,000 candle power and had a maximum range of 17,000 yards (15,540 m).

7) As built the "Specials" carried about 150 rounds per gun.  After the rebuilds following the investigation into the capsizing of the torpedo boat Tomozuru and weather-related damage to other ships in 1935, stowage was reduced to 120 rounds per gun.

Single Mounts
   Hatsuharu (1):  Type A
   Shiratsuyu (1):  Type B

Single Mounts
   Type A:  -7 / +55 degrees
   Type B:  -7 / +55 degrees

1) These mountings were well liked but were considered to need strengthening, which may have been the cause of the large amount of dispersion noted.

2) Most surviving destroyers had "X" mount removed during the war in order to fit additional 25 mm AA guns.

3) In addition to being weather and splinter proof, these mountings were also proof against poison gas.

4) The "Special Type" destroyers are usually split into the Fubuki (first 10), the Shikinami (second 10) and the Akatsuki (last 4) sub-classes.  Regarding weaponry, the difference between these sub-classes was that the Fubuki had SP guns, while the Shikinami and the Akatsuki had DP guns.

5) Single and twin mounts had a pusher shell hoist for each gun.  Twin mounts had the guns individually sleeved.  Charges for both single and twin mounts were passed by hand.

6) Crew was 10 for the single mounts and 16 for the twin mounts.

7) Although the loading angle was unimpressive for AA use, it should be noted that +10 degrees was sufficient for most surface actions of World War II.

8) The Hatsuharu class originally had their single gun superimposed on the bow as can be seen in the photograph above.  Following trials with the first two class members where their stability was found to be poor and the investigation into the capsizing of the torpedo boat Tomozuru, these ships were greatly modified to improve their stability.  As part of these changes, the single gun was repositioned on the weather deck directly in front of the stern twin mount.  The four other members of the class still under construction were completed to the new arrangement.