1/144 5.25"/50 (13.4 cm) QF Mark I Guns 1943 x4

1/144 Scale Royal Navy Dual Purpose 5.25"/50 (13.4 cm) QF Mark I Gun 1943 x4. These are highly detailed parts for anyone wishing to build a KGV Class or Dido Class vessel). The 1943 upgrades have extra ventilation on the front and access hatches set in cupolas on the mounting roof.

• 4x Mountings
• Highly detailed, accurate parts, modelled from plans and photographic reference.
• Barrels are printed separately and can be angled as desired
• details include Hex nuts, open sighting ports, accurate venting and access hatches

Historial Information
This gun was used as a Dual-Purpose (DP) secondary on the King George V and Vanguard battleship classes and as the main guns on the Dido and Spartan cruiser classes. This was a somewhat large caliber for a DP gun, but chosen because it was considered that this size would provide the maximum weight of shell that could still be manually handled by the average gun crew. Unfortunately, the original design of the gunhouse was cramped and the heavy projectile and cartridge cases resulted in a lower rate of fire than expected. In addition, the slow elevating and training speeds of the mounts were found to be inadequate for engaging modern high-speed aircraft.

The later mountings designed for HMS Vanguard enjoyed a much improved RPC system and were coupled with the USN's outstanding Mark 37 fire control system which eliminated the manually-operated fuze-setters in the previous mountings, giving the gun crews a roomier working space. However, Vanguard did not see service until long after World War II had ended and she was destined never to fire her guns in anger.

"A" turret in the early Dido class cruisers was prone to jamming with some thirteen separate incidents being reported during 1940-41, including that of HMS Bonaventure while engaging the German heavy cruiser Admiral Hipper in December 1940. These problems were mainly the result of the light construction methods used on most Treaty-limited ships, which in this case allowed the bow to flex in heavy weather or during high-speed turns. This was rectified in the early ships by stiffening the bow section and by more careful attention to the detail fitting work required for installation of the mountings. Later ships had these modifications incorporated during their construction and no problems of this nature were encountered for these cruisers. It is also recorded that after the winter of 1941 the captains of the early ships "handled them appropriately" during heavy weather which also alleviated the problem. However, in 1950 HMS Euryalus had A turret permanently out of action due to problems with the roller path.

These mountings proved difficult to manufacture and the King George V battleships were given the highest priority of what guns and mountings were produced. As a result, the Dido class cruisers HMS Charybdis and HMS Scylla were completed with eight 4.5" (11.4 cm) guns and three other cruisers, including HMS Dido herself, were completed with only eight 5.25" (13.4 cm) guns. HMS Dido had her fifth turret installed during a refit late in 1941 at the Brooklyn Navy Yard, while HMS Bonaventure was sunk in March 1941 and HMS Phoebe remained an eight-gun cruiser. The later Spartan class were designed from the start with eight guns.

D.K. Brown, RCNC, noted that his experience in HMS Euryalus was that these mountings were "generally unreliable."

Constructed of autofretted loose barrel (no liner), jacket to 99 inches (2.5 m) from the muzzle, removable breech ring and sealing collar. Used a hand-operated horizontal sliding breech block with semi-automatic opening. It was necessary to dismount the gun in order to change barrels. A total of 267 guns were manufactured of which six were loaned to the Army.

Nomenclature notes: The 5.25" (13.4 cm) Mark II, Mark III and Mark V were Army AA guns with a higher muzzle velocity. Only a few of these guns were manufactured. A further naval development, the Mark IV gun in the Mark III twin mounting, was to have vertical-sliding breech blocks, fire fixed ammunition and have a much higher rate of fire. Two experimental guns were ordered in 1944, but the mounting never progressed beyond the sketch stage. A postwar project for a twin Mark III mounting capable of 70 RPM using fixed ammunition did not make it off the drawing board.

Cleaning Information
Some part cleanup will be necessary. The 3D printing process uses a waxy substance to support certain part features during the printing process. Although the parts are cleaned by Shapeways, some waxy residue may remain.  It can be safely removed with water and a mild aqueous detergent like "Simple Green" using an old, soft toothbrush, Q-tips or pipe cleaners. During the printing process, liquid resin is cured by ultraviolet light. Microscopic bits of resin may remain uncured.

Let your parts sit in direct sunlight for a few hours to fully cure the resin.  
Water-based acrylic paints meant for plastics is strongly recommended. Other paints, especially enamels, may not cure on Frosted Detail 3D-printed plastics.
Use dedicated model sprue cutters to remove parts to minimise the risk of damage to parts.
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