4.5-inch gun data sheet

BRITISH ARTILLERY IN WORLD WAR 2

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 It was withdrawn from service at the end of the war when 5.5-inch became the standard medium equipment.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.

Calibre	4.5 inches	Ordnance length Bore length	192.75 inches 42 calibres	Rifling	32 grooves, 1 in 25 uniform twist	Chamber capacity	537 cubic inches
Barrel	Autofrettaged loose liner	Breech	Welin screw & Asbury mech	Recuperator	Hydro-pneumatic	Sights	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	6/10	Body Diameter	4.485 inches	Driving Band Diameter	4.72 inches	Weight (incl fuze)	55 lbs	Explosive Weight	3.9 lbs

Charge

New Gun MV

RT MV

RT Max Range

Time of Flight @ Max Range

Probable Error @ Max Range

Approx Propellant Weight

1	1275 f/s	1250 f/s	11,100 yds	47 secs	50 yds	3 lbs
2	1810 f/s	1750 f/s	15,000 yds	48 secs	35 yds	6 lbs
3	2265 f/s	2250 f/s	20,500 yds	69 secs	60 yds	9 lbs

Rates of fire	Gunfire	Intense	Rapid	Normal	Slow	Very slow
Rounds/Minute	2 to 3	2	1�	1	²/3	¹/3

Normal Detachment

10 men

Gun Tractor

Medium Artillery Tractor 4 � 4 (Matador)

Artillery Trailer

None

1st Line Ammo (per gun)

100 HE

VARIANTS

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	Layer	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:
26/Manuals/2964 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,

Handbook
226/Pubs/71 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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