1) The prefix "A" is sometimes found and indicates the use of a "pure couple" breech mechanism.

2) The Rate of Fire figure given above is found in references, but "Warrior to Dreadnought:  Warship Development, 1860-1905" quotes Jellicoe's 1906 figures for rates of fire for these guns in gunlayers' tests and in battle practice and notes that the latter figures corresponded well to those actually attained by the Japanese at Tsushima:

Gunlayers Test:  5 rounds per minute
Battle Practice:  2 rounds per minute

3) When used in monitors, the ROF is quoted at 1 round per minute.  Most coastal guns also had a ROF of about 1 round per minute.

4) Danger space for this gun against a 30 foot (9 m) target was estimated as follows:
   75 yards at   8,000 yards (69 m at   7,300 m)
   30 yards at 12,000 yards (27 m at 10,970 m)
     0 yards at 16,000 yards (  0 m at 14,630 m)

5) The monitors used spare guns and mountings originally intended for regunning Drake class cruisers.

World War II
   Standard charge:  109 lbs. (49.4 kg) SC150
   Super charge:  123.6 lbs. (56.1 kg) SC205

Standard charge:  2,748 fps (838 mps)
Super charge:  2,872 fps (875 mps)

1) MD charges were used prior to and during World War I while standard and super charges were used by coastal batteries during World War II.

2) Original shells were all 2crh.  During World War I, 4crh projectiles were developed for the monitors.  Coastal artillery was supplied with 5/10crh shells during World War II.

3) The following comments are by Nathan Okun:

The British Coast Defense Gun 9.2" APC shell weighed 380 lb and had a 3.4% filler (12.9 lb) for all versions made during World War I and World War II.  The last version, the 9.2" Mark XIIA APC, had two versions, one made in Britain and one made in the US during World War II by Crucible Steel Company.  The US version was identical to the British version as to the body shape, base plug, weight, and windscreen, but the nose of the shell was the US Navy early World War II very blunt point and it used a US-style early World War II AP cap and, I believe, the US Sheath Hardening Pattern, not the British more deformable World War II APC hardness pattern.  Under test the US design satisfied all ballistic test specifications, though the base plug was exposed more by base slap breakage at oblique impact as it penetrated than the British softer lower body was.  The British cup-shaped Patent Relief Base Plug worked though and both the US and British designs were still effective ("fit to burst") after penetrating the armor. 

The post-World War I designs all used Shellite fillers, though those during World War I were much like their contemporaries and used Lyddite prior to 1918 and Shellite afterwards (there was a Greenboy version of this projectile, too).

I would have thought that with this large cavity, which was exactly the same as in World War I, the 9.2" Mark XIIA APC would have had problems with projectile breakup against thick armor at moderate obliquity (circa 1-caliber-thick plate at around 30 degrees obliquity).  However, this was not the case.  In fact, these projectiles -- both the US and British designs -- are, from the tests I have seen, THE BEST BRITISH APC PROJECTILES EVER MADE!!  They penetrate armor better and remain in one piece under more extreme impact conditions (I even gave them a separate entry in FACEHARD's British projectile table).  I have no idea why they were so good.  Obviously there are "sweet spots" for every kind of mechanical design and this shell happens to be right on top of one.

1) The gun mounting manual for this weapon says that the gunsights were calibrated up to 14,000 yards (12,800 m) which was for a 15 degree elevation and a muzzle velocity of 2,643 fps (806 mps).

2) The first supercharge figure is from "Naval Weapons of World War Two" while the other is from "The Naval Institute Guide to World Naval Weapon Systems 1991/92."  This may reflect the performance of different shell types.

3) As built, naval mountings were only able to elevate to +15 degrees.  Mountings later fitted to the monitors were modified to allow +30 degrees maximum elevation.  See Mount / Turret notes, below.

  Monitors (1):  Mark V (modified)

Reworked Monitor Mountings:  -5 / +30 degrees

Army Coastal Artillery: -5 / +15, +30 or +35 degrees

1) Four spare Mark V mountings were reworked for the monitors by having their armor replaced with thin sheet steel and the rear of the shield removed entirely in order to reduce weight.  Hydraulic machinery was also removed for the same reason and these mountings thus became completely hand worked.  These changes reduced the total revolving weight by about 40 tons (41 mt).

2) HMS Commonwealth and HMS Zealandia (King Edward VII class) and the monitors had their mountings modified to give +30 degrees maximum elevation.

3) Early in 1917 three Mark VS mountings altered to give +45 degree elevation were installed on the Belgian coast.

4) Mark V mountings were built by Elswick while Mark VI mountings were built by Vickers.