Updated  14 June 2014

Conversion factors to metric measurement

 Ordnance, B.L. 4.5-inch Gun Mk 2 on Carriage Mks 1 & 2


 The 4.5-inch Gun was one of the two British medium guns of World War 2, which both used the same carriage, the other being the 5.5-inch.  The original Mk 1 gun was developed in the mid 1930s and used a modified 60-pr carriage, most were lost in France in 1940 but some served in N Africa.  The 4.5-inch was the replacement for the 60-pr Gun, its primary role was counter-battery fire.
The gun and ammunition were an early agreement between UK and US, being matched with the US 4.5-inch Gun M1.  Ballistically there was virtually no difference between the Mks 1 and 2 guns.  The Mk 2 gun first entered service in 1941, while its range made it very useful for CB its shells lacked lethality, although given its CB role its fewer and larger fragments may have been appropriate. It is difficult to distinguish from the 5.5-inch, the only visible difference being a barrel about 2 feet longer on the 4.5-inch.  It was only used by British and Canadian regiments in Europe and North Africa.   It was withdrawn from service at the end of the war when 5.5-inch became the standard medium equipment. This 4.5-inch Gun had nothing in common with the 4.5-inch Howitzer or the 4.5-inch AA or Naval guns.


 4.5 inches

Ordnance length
Bore length

 192.75 inches
42 calibres


 32 grooves, 1 in 25 uniform twist

Chamber capacity

 537 cubic inches


 Autofrettaged loose liner


Welin screw & Asbury mech




 Calibrating &  reciprocating

Carriage configuration

 Split trail

Max elevation

  - 5 to 45

Top traverse

 30 Left & Right

Loading Angle


Basic Weight

 5.8 tons

Length (muzzle to towing eye)

 26.5 feet

Trunnion height

 4.3 feet

Width at wheel hubs

 8.3 feet

Standard HE Shell Mk 1D

Length (less fuze)

 18.9 inches

Calibre radius head


 Body Diameter

 4.485 inches

Driving Band Diameter

 4.72 inches

Weight (incl fuze)

 55 lbs

Explosive Weight

 3.9 lbs


New Gun MV


RT Max Range

Time of Flight @ Max Range

Probable Error @ Max Range

Approx  Propellant Weight



 1275 f/s

1250 f/s

11,100 yds

47 secs

 50 yds

3 lbs



 1810 f/s

1750 f/s

15,000 yds

48 secs

 35 yds

6 lbs



 2265 f/s

2250 f/s

20,500 yds

69 secs

 60 yds

9 lbs


Rates of fire






Very slow


 2 to 3






Normal Detachment

 10 men

Gun Tractor

Medium Artillery Tractor 4  4 (Matador)

Artillery Trailer


1st Line Ammo (per gun)

 100 HE


There were no significant variants, different marks of ordnance were minor internal modifications.  The carriage marks reflected increasing using of welded instead of riveted assemblies.
A comparison of UK Range Tables and US Firing Tables for this gun reveal interesting differences, the US used only 2 charges Normal, equivalent to Charge 2 and Super equivalent to Charge 3.  However, the MVs (1820 f/s and 2275 f/s) and hence tabulated maximum ranges are greater due to national differences in standard conditions and methods of deriving corrections for them.
Some US barrels may have been provided to Canada and fitted with UK breach rings, blocks and modified slides.  Consideration was given to adopting the US 4.5-inch SP gun T16 but this was rejected.

Picture List

Gun Detachment duties in action:

No 1

Detachment Commander

No 2

Operate breech, load lock, fire gun

No 3


No 4

Load and ram

No 5

Load and ram

No 6

Prepare cartridges

No 7

Prepare shells

No 8

Prepare shells

No 9

Prepare shells

No 10

Coverer, supervise ammunition

Equipment Publications:
Range Tables Part 1:
HE, Mk 1D (Streamline), 1942.

Gun Drill:
26/Manuals/1373   BL 4.5-inch Mk 2 Gun, 5.5-inch Mk 3  Gun on Carriage 5.5-inch & 4.5-inch Mks 1 & 2, 1945
(WO Code 7348)

WO Code 8902    BL 4.5-inch Mk 2 Gun, 5.5-inch Mks 3 & 4 Gun on Carriage 5.5-inch & 4.5-inch Mks 1 & 2, 1955 

WO Code 9090      BL 4.5-inch Mk 2 Gun, 5.5-inch Mks 3 & 4 Gun on Carriage 5.5-inch & 4.5-inch Mks 1 & 2,

   Ordnance, BL, 4.5-inch Mk 2 on Carriage 5.5-inch or 4.5-inch Gun Mk 1 (Provisional), 1941.
26/Manuals/3143  Ordnance, BL, 4.5-inch Mk 2 & 2* on Carriage 5.
5-inch or 4.5-inch Gun Mk 1 & 2, 1943
(WO Code 801)

Maintenance Manual
26/Manuals/3143  Ordnance, BL, 4.5-inch Mk 2  & 2* on Carriage 5.
5-inch or 4.5-inch Gun Mk 1 & 2, 1943
(WO Code 896)  

Identification List:
26/Manuals/2961     Ordnance BL 5.5-inch Mk 3  & 4.5-inch Mk 2 on Carriage 5.5-inch & 4.5-inch Mk 1, 1944
                              Ordnance BL 5.5-inch Mk 3  & 4.5-inch Mk 2 on Carriage 5.5-inch & 4.5-inch Mk 2, 1945



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