BRITISH ARTILLERY IN WORLD WAR 2

 7.2-INCH HOWITZER

Updated  14 June 2014

Conversion factors to metric measurement

 B.L. 7.2-inch Howitzer Mks 1, 1*, 2, 3 and 4 on Carriage 7.2-inch Howitzer Mk 1

 Picture List

The 7.2-inch Howitzer was derived from the WW1 8-inch Howitzer, which had insufficient range.  Various shell weights and calibres of 7 and 7.4-inch were initially considered, 7.2-inch was selected in November 1940 and the design approved in April 1941.  The different 7.2-inch ordnance Mks were various lined down 8-inch barrel Mks, a new build monobloc barrel was initially developed but lining down was adopted because it was cheaper. The carriage was that of the  8-inch How/6-inch Gun modified with modern sights, pneumatic tyred wheels and brakes for vehicle towing (the WW1 original had been towed by Holt tractors).  Barrel Mk 1 was monobloc, Mks 2 - 4 were lined down 8-inch barrels Mks 6 - 8. A distinctive feature of the Mk 1 carriage was the use of large scotches behind the wheels and smaller ones in front, these were essential when firing charge 4.  

7.2-inch equipped heavy batteries from mid 1942.  In Burma they were provided as a  'pool' of  2 guns per corps and usually operated by HAA or medium regiments as required.   During WW2 7.2-inch was only used by RA regiments, including those of Newfoundland.  Regiments using these guns are listed here and here.  Mks 1 - 4 went out of service at the end of WW2 but Mk  6 (see below) equipped post-war heavy regiments and remained in British service until the early 1960s and in Indian service for several years after that.

Calibre

 7.2 inches

Ordnance length
 Bore length

 171 inches
 22.4 calibres

Rifling

 40 grooves, 1 in  20 uniform twist

Chamber capacity

 1186 cubic inches

Barrel

Autofrettaged loose liner (except Mk 1)

Breech

Welin screw & Asbury mech

Recuperator

Hydro-pneumatic

 Sights

 Calibrating &  reciprocating

Configuration

 Box trail

Max elevation

 45°

Top traverse

4° Left & Right

Loading angle

  7.5°

Basic Weight

 10.1 tons (Mks  varied)

Length (muzzle to towing eye)

 25.4 feet

Trunnion height

 4.3 feet

Width at wheel hubs

 9 feet

Standard HE Shell Mk 3D

Length (less fuze)

 35.07  inches

Calibre radius head

 5/10

Body Diameter

 7.185  inches

Driving Band Diameter

 7.47 inches

Weight (incl fuze)

 202 lbs

Explosive Weight

 28 lbs

Charge

New Gun MV

RT MV

RT Max Range

Time of Flight @ Max Range

Probable Error @ Max Range

Approx  Propellant Weight

 1

 902 f/s

 875 f/s

7,500 yds

7 lbs

 2

 1054 f/s

 1025 f/s

9,400 yds

 41 secs

55 yds

9 lbs

 3

 1385 f/s

 1350 f/s

13,500 yds

 52 secs

 60 yds

15 lbs

 4

 1697 f/s

 1675 f/s

16,900 yds

 59 secs

70 yds

 24 lbs

Rates of fire

Gunfire

Intense

Rapid

Normal

Slow

Very slow

Rounds/Minute

 1

 1

 ½

 ¹/3

 ¼

¹/8

Normal Detachment

 10 men

Gun Tractor

Heavy Artillery Tractor 6× 6

Artillery trailer

 None

1st Line Ammo (per gun)

 56 HE

VARIANTS

In 1943 heavy regiments reorganised to have 2 batteries of 7.2-inch howitzers and 2 of US 155-mm guns M1.  This led to the adoption of the M1 carriage for 7.2-inch, a possibility that had been idenified in 1942.  Mk 5 was the existing ordnance modified for the M1 carriage and does not seem to have entered service.  Mk 6 was a new, longer barrel, for use with the M1 carriage and introduced in early 1945.  This barrel was monobloc construction.  The existing charges 1 - 4 were retained with a new charge 5 added, the significantly larger chamber resulted in lower MVs despite the barrel being longer than Mks 1 - 5.  Mks 5 and 6 did not have calibrating sights. UK had sought 155mm carriages from the US in 1943-4 but US production delays meant they did not become available until 1944.

 Ordnance, B.L. 7.2-inch Howitzer Mk 6 on Carriage 155 mm and 8-inch M1 

Calibre

 7.2 inches

Ordnance length
Bore length

 248 inches
 33.1 calibres

Rifling

 40 grooves, 1 in  20 uniform twist

Chamber capacity

 1800 cubic  inches

Barrel

 Monobloc

Breech

 Welin screw &  Asbury mech

Recuperator

Hydropneumatic with nitrogen

 Sights

 Reciprocating
 Separate laying

Carriage configuration

 Split trail

Max elevation

  -1°50' to  63°

Top traverse

 30° Left & Right

Loading angle

7.5°

Basic Weight

 17.5 tons

Length (muzzle to towing eye)

  34 feet

Overall height

  feet 8.3 feet

Width of bogie

 8 feet

Standard HE Shell

Charge

New Gun MV

RT MV

RT Max Range

Time of Flight @ Max Range

Probable Error @ Max Range

Approx  Propellant Weight

 1

886 f/s

875 f/s

7,170 yds

37 secs

 50 yds

7 lbs

2

 1034 f/s

 1025 f/s

9,460 yds

43 secs

 35 yds

9 lbs

3

1341 f/s

1350 f/s

13,210 yds

52 secs

30 yds

15 lbs

4

 1629 f/s

 1675 f/s

16,630 yds

59 secs

 55 yds

24 lbs

5

 1974 f/s

 1925 f/s

19,667 yds

65 secs

 45 yds

31 lbs

 Separate cartridge

Rates of fire

Gunfire

Intense

Rapid

Normal

Slow

Very slow

Rounds/Minute

 1 +

1

1

½ 

¹/3

¹/6

Normal Detachment

 13 men

Gun Tractor

Heavy Artillery Tractor  6× 6

Artillery trailer

 None

1st Line Ammo (per gun)

 56 HE

B.L. 7.2-inch Howitzer Mk 4 on Carriage 7.2-inch Howitzer Mk 1  - a studio picture without scotches in
B.L. 7.2-inch Howitzer Mk 6 on Carriage M1 - spades not fitted

No 1

Detachment Commander

No 2

Operate breech, load lock, fire gun

No 3

Layer

No 4

Traverse trail, ram

No 5

Traverse trail, ram

No 6

Prepare & load cartridge

No 7

Traverse trail, ram, ammo

No 8

Traverse trail, ram, ammo

No 9

Ammo

No 10

Coverer, ammo

No 1

Detachment Commander

No 2

Operate breech, load lock, fire gun

No 3

Lay for line, gun rule

No 4

Lay elevation

No 5

Lay elevation

No 6

Prepare & load cartridge

No 7

Prepare shell, loading tray

No 8

Prepare shell, loading tray

No 9

Prepare shell, loading tray, ram, sponge

No 10

Prepare shell, loading tray, ram

Prepare shell, ram

Prepare shell, ram, fuze indicator

Coverer

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