Some data on the 4.5 inch guns and ammo from Campbell's classic Naval Weapons of World War Two, plus other sources:
The guns were given separate Mark numbers from their mountings, which complicates matters. The guns first:
Mk 1: breech design very similar to 4.7 inch Mk XII but with ignition modified to electric by omitting the percussion elements.
Mk II: army AA weapon, generally similar to navy guns.
Mk III: interchangeable with Mk I, differed only in that it was designed for electric firing only.
Mk IV: modified to suit use in converted 4.7 inch Mk XII mountings (destroyer single mountings).
Mk V: postwar gun introduced in 1947, although much development during the war. Different breech design with faster loading cycle, designed for separated ammunition. The standard gun until the automatic Mk 8 came along.
Mountings (main types only - there were variations):
Mk II BD (between decks - slightly recessed installation) HA mounting with two Mk I or Mk III guns, used in various aircraft carriers and modernised capital ships. Fixed ammo used (114 x 696R)
Mk III UD (upper deck) - HA mounting with two Mk I or Mk III guns, used in various ships. Fixed ammo used (114 x 696R).
Mk IV - HA mounting with two Mk III guns, in Battle class destroyers (separated ammo, 114 x 644R)
Mk V - LA destroyer mounting with single Mk IV gun (separated ammo, 114 x 644R)
Mk VI - postwar HA mounting with two Mk V guns (later both gun and mounting were redesigned Mk 6); the "rounded cube" turret as fitted in 1960s destroyers and frigates. (separated ammo, 114 x 644R)
Mk 8 - 1970s automatic gun/mounting, 114 x 700R fixed ammo.
So apart from the postwar Mk 6 and Mk 8, whether or not the ammo was fixed or separated depended on the mounting, not the gun - no doubt the cause of some confusion!