Unfortunately, the very low muzzle velocity of this gun gave it a rather short range, about half of what was really desired, and shipboard firing trials with it were not very successful. Nonetheless, it was approved, although it did not enter service until long after the end of the war, and was used on MTBs and MGBs for the next fifteen years.
Constructed of barrel, removable breech ring and vertical sliding breech block with semi-automatic operation. The original naval order was for three prototypes and 106 guns. In September 1945 the Navy agreed to accept all 98 guns that had been finished, even though the requirement at that time was only 60 guns. A total of 36 Mark I mountings were actually completed along with a very few Mark II mountings.
Postwar, the British tried to develop a stabilized mounting for this weapon, designated as CFS-1 (Coastal Forces System Mark 1). The weight of this mounting grew alarmingly with "improvements" and did not see service use.
Actual bore length was 18.88 calibers. All British 4.5" naval guns have an actual bore diameter of 4.45" (11.3 cm).
Nomenclature note: CFS-2 was a stabilized mounting utilizing the 20-pdr (3.28" or 83.4 mm) Centurion tank gun. Although lighter than the CFS-1, it was still too heavy for coastal craft and did not see service use. Prototype was on Bold Pioneer, a photograph of which makes one wonder how the ship could be steered, as the gunhouse blocks much of the forward view.
HMS Bold Pathfinder as MGB in 1953
|Designation||4.5"/19 (11.4 cm) 8cwt QF Mark I|
|Ship Class Used On||MTB 509, 520, 528, 530, 538, 790, 2014, 2017, 5007 and 5008|
|Date Of Design||1944|
|Date In Service||1946|
|Gun Weight||0.400 tons (0.406 mt)|
|Gun Length oa||89.1 in (2.262 m)|
|Bore Length||84.0 in (2.134 m)|
|Rifling Length||73.49 in (1.867 m)|
|Twist||Uniform RH 1 in 25|
|Chamber Volume||137.5 in3 (2.253 dm3)|
|Rate Of Fire||10 rounds per minute cyclic|
|Note: First entered service on MTB 509 and 528 in April 1946.|
|Weight of Complete Round||N/A|
|Projectile Types and Weights||HE - 22 lbs. (10 kg)|
|Bursting Charge||5.5 lbs. (2.5 kg)|
|Projectile Length||19 in (48 cm)|
|Propellant Charge||1.148 lbs. (0.52 kg) NQ/R 014 x 048|
|Muzzle Velocity||1,500 fps (457 mps)|
|Approximate Barrel Life||N/A|
|Ammunition stowage per gun||N/A|
1) Mark I mounting carried seven ready rounds.
2) Cartridge cases for this weapon were apparently cut-down 3.7" (9.4 cm) AA cases.
|Elevation||With 22 lbs. (10 kg) HE Shell|
|Range @ 10 degrees||3,300 yards (3,020 m)|
|Note: Although the Mark I mounting could elevate to +12 degrees, the gun was only sighted to 9 degrees 58 minutes.|
MTBs (1) and MGBs (2): Mark I
Prototypes: Mark II
|Weight||Mark I: 1.738 tons (1.766 mt)
Mark II: N/A
|Elevation||Mark I: -10 / +12 degrees
Mark II: -10 (?) / + 30 degrees
|Train||about +150 / -150 degrees|
|Train Rate||Mark I: 25 to 30 degrees per second
Mark II: Manually operated, only
|Gun recoil||Mark I: 29 to 30 in (74 to 76 cm)
Mark II: N/A
1) The Mark I was developed from a powered twin Oerlikon mounting and was hydraulically powered from a pump driven by the auxiliary or main engines. This conversion proved to be underpowered when faced with the much heavier 4.5" (11.4 cm) gun barrel and was found to be unable to ensure proper tracking in rough weather. In an emergency, a manual pump located on the mounting could be used. This mounting included a launcher for firing illumination rockets.
2) The Mark II was a lighter, manually operated mounting that saw limited service use.
3) Note the long recoil stroke for the Mark I, which reduced the blow to the lightly constructed MTBs.
21 November 2008 - Benchmark
12 February 2012 - Updated to latest template