The South African
Military History Society
Die Suid-Afrikaanse Krygshistoriese Vereniging


Military History Journal
Vol 2 No 6 - December 1973

Field Artillery of the British Army 1860-1960
Part III, 1914—1960

Major Darrell D. Hall

Parts 1 and II, 1860-1914, were published in Vol 2, Numbers 4 and 5.

This period deals primarily with the field guns of the two World Wars, the 18 pr and the 25 pr. After the frequent changes of earlier years, these were guns which remained in service for about 30 years each.

The steps leading to the adoption of the 18 pr have already been described. The 18 pr was the British Army’s field gun when the war started in 1914. At that time it was thought that this would be a war of movement and that the 13 pr, 18 pr and 4.5in howitzer would adequately cater for the needs of the army in the field. Of course, heavier guns were also available.

When trench warfare developed and it became apparent that it would be a static war, more and more emphasis was placed on heavier calibres and heavier shell weight. Many heavy guns came into service, but the 18 pr was the gun which was produced in greater numbers than any other. Consequently more 18 pr shells were fired than any other calibre. For example, although 22,400,000 shells were fired by the 6in 26 cwt BL howitzer, more than 100 million 18 pr shells were fired.

At first only shrapnel and star shells were available, but a request was soon made for a high explosive shell. This shell came into use in 1915.

Both the 18 pr Mk I and Mk II carriages had pole trails. These limited elevation to 16°, and so range was limited to 6525 yds. Towards the end of the war a Mk III carriage appeared with a box trail. This allowed elevation to 30° and range was increased to 9300 yds. It was followed quickly by a Mk IV carriage with elevation to 37° and a range of 10,800 yds. The gun (as opposed to carriage) was also improved, and the Mk IV gun appeared on both the Mk III and IV carriages, with an improved breech mechanism.

There were other carriage modifications as well, notably to the recoil system. The buffer and recuperator were mounted under the piece. The cradle was lengthened to provide better support for the gun during recoil, and this recoil was variable depending on the elevation. This meant that at maximum elevation the gun could be fired without any chance of the breech hitting the ground on recoil.

Very few Mk IVs saw service during the war, but this was the version which was in use between the wars until it was replaced by a Mk V carriage. This had a split trail which allowed a 500 traverse. This was very useful for anti-tank shooting, but it was slow in and out of action, and it was difficult to handle. Consequently, when a circular platform was produced for the Mk IV carriage, the Mk V was dropped. This circular platform was carried under the Mk IV trail. It provided a simple method of achieving quick and extensive traverse.

During the ‘20s and ‘30s plans were made for the modernising of the British Army’s field artillery. It was decided to replace the 13 pr, 18 pr and 4.5in howitzer with one all-purpose gun which would fire one shell with variable charges, enabling it to cover the roles of the three World War I equipments. it was also decided to dispense with shrapnel as the improved fragmentation of the HE shell made the retention of shrapnel unnecessary.

By 1930 the basic design of the new gun had been accepted. It was to have a calibre of 3.45in and it would fire a 25 lb shell. This calibre was a compromise, dictated to a large extent by economy. There were many 18 pr pieces still in existence, and they could be re-bored to the new calibre pending the introduction of the completely new equipment. Also, as the 18 pr Mk IV carriage could accept the greater recoil stresses of the heavier shell, it could be used until the arrival of the carriage designed for the new gun.

This interim version was known as the Ordnance 3.45in but it was referred to generally as the 18/25 pr. The official title was soon changed to 25 pr Mk I. Sufficient of these were made available to equip the army.

Much thought was given to the design of the carriage for the new gun. A split trail was considered; and abandoned. Finally the designers agreed on a box trail which had been planned for a 105mm howitzer, which was the equipment which the designers would have preferred but which, as explained, economy did not allow.

This box trail was splay-sided to allow for maximum traverse 80 in all. Secondly it was hump-backed, to allow a 360 degree firing platform to be carried underneath it. This was similar to the platform produced for the 18 pr Mk IV carriage and was like a large wagon wheel. On coming into action, the gun wheels were pulled upon it. One man could then lift the trail by the handspike and, if required, move the gun through a complete circle.

The new equipment was designated the 25 pr Mk II. It was not produced in quantity until February 1940, and it first saw action in Norway in April 1940. The British Expeditionary Force in France had the earlier 18/25 pr, and most of these were lost in that campaign. The gun with which most British and Empire field artillery units fought the war from then on, was the 25 pr Mk II.

The 25 pr had a detachment of six. It was towed into action by a vehicle which, because of its shape, was known as a ‘quad’. It looked as if it was armoured, but it was not. The quad towed the gun and a ‘trailer artillery’ or limber which carried 32 rounds.

Many types of ammunition were produced HE, armour piercing (AP) shot, star, incendiary, smoke, flare and, should it be necessary, chemical. There were four charges, 1, 2, 3 and super. Maximum range with super charge was 13,400 yds. The 18/25 pr on the 18 pr Mk IV carriage was not robust enough to deal with this charge, so its maximum range was limited to 11,800 yds.

Only limited numbers of super charge were carried for each gun, as this charge caused excessive wear. This meant that effective range was considered to be something less than 11,800 yds, the maximum range with charge 3.

Armour piercing shot was produced at the time of the North African campaign. For this, an incremental charge was provided which gave the greater muzzle velocity required to propel the shot faster and further. As it made the gun unstable, a muzzle brake was fitted. The 25 pr achieved some success as a tank killer in the Western Desert.

25 prs used by the Australians and New Zealanders in the Far East did not have to contend with tanks to the same extent, and so their 25 prs were not fitted with the muzzle brake.

The 25 pr weighed nearly two tons, and this weight presented problems for some units. It was too heavy for airborne units and so they were equipped with the American 75mm howitzer Ml. This remained the gun of British airborne forces until 1955.

For the jungles of the Far East the Australians produced a ‘baby 25 pr’. This had no shield, a cut-down barrel with flash hider and a shortened trail with a castor wheel for easy manoeuvring. As the shortened barrel interfered with the ballistics, range was limited to 10,800 yds.

The Indian Army also modified the gun. Their version had a short axle but retained the original barrel, for the sake of the additional range.

The Canadians then produced a hinged trail. This was combined with the Indian short axle, and the result was the Mk III carriage.

Various self-propelled (SP) versions of the 25 pr were produced, but the most successful was the Sexton on a Canadian Ram chassis. This was the main field artillery SP gun of British armoured divisions in the last years of the war.

The 25 pr will be remembered with affection by thousands of war-time gunners and by the troops they supported. Reliable and accurate, this was a Rolls-Royce among guns. It remained in service for many years after the war and, in the South African Army, it is still in use. It was used in Korea and Malaya, and in other trouble spots which required British action in the late ‘40s and in the ‘50s.

The post-war years saw the armies of the world preparing for nuclear warfare, and the Communist threat saw the establishment of NATO. It was considered that the nuclear battlefield would see a war of movement with infantry moving in armoured personnel carriers. Such conditions would require all artillery to be self-propelled with complete overhead protection against nuclear fall-out. In addition, NATO membership required a standardisation of ammunition. In the case of field artillery the calibre adopted was 105mm. Apart from its calibre (88mm or 3,45in) being unacceptable, the 25 pr’s shell was also considered to be too light and its range too short. Work therefore proceeded on the design of a new self-propelled gun with a l05mm calibre for the British Army of the Rhine (BAOR). This gun, known as Abbot, appeared in the ‘60s and is still in use.

However, the first demand for a change came from the airborne gunners who, in 1955, had received the 25 pr in place of the American 75mm, as the 25 pr could now be parachuted with a suitable towing vehicle. In spite of this capability, when British airborne troops next parachuted into action at Suez in 1956, the guns were not dropped with them, but arrived later by landing craft. This was because of difficulties experienced by the RAF with the transport aircraft concerned. This was obviously not acceptable, and soon afterwards airborne gunners received the 4,2in mortar which could easily be parachuted from more than one type of aircraft. In 1957 the 75mm came back for a few years for use in Aden.

The 4,2 in mortar was originally produced in World War II to fire chemical bombs. It was later adopted as an infantry support weapon and HE bombs were developed. After the war it was handed over to the Royal Artillery. It was used by gunners in Korea, but it was never completely accepted as a gunner weapon. Its range was short — just over 4,000 yds and bomb weight was only 20 lbs, although its lethal effect was considerable. A mortar bomb does not have to cope with the stresses of a rifled barrel, and so its casing can be thinner and explosive content correspondingly greater. Measures were taken therefore to replace the mortar as soon as possible with a NATO-approved 105mm gun.

The pattern at this stage was for BAOR regiments to receive the Abbot SP 105mm, and for so-called strategic reserve regiments to be equipped with this new 105mm. Strategic reserve regiments were those in the Parachute and Commando Brigades and certain other nominated regiments, all of which were ready for rapid despatch to any part of the world.

The equipment selected for these regiments was an Italian 105mm pack howitzer. It was a good gun but its range was only 10,800 yds. It was easily air-portable and helicopter-borne and was parachutable. Shell weight was 33 lbs and there was a wide range of shell types. The gun could be stripped down to mule or man loads very quickly. This was an essential characteristic when manhandling was necessary in the Borneo jungle during the Indonesian Confrontation between 1962 and 1966. The 105 weighed 1,25 tons. When stripped, the heaviest part was the cradle and recoil system which weighed 269 lbs. A good detachment could reassemble the gun and get a round away in 2.5 minutes.

The 105 was not designed to be towed extensively, as its axle was rigid and, being a pack equipment, the shocks and stresses of movement over rough ground caused considerable wear to its various parts. In training, therefore, the gun had to be moved by porte for distances of more than 25 miles. This was not as great a disadvantage as it might appear as, more often than not on active service, it came into action by helicopter or parachute.

  Type Weight of complete equipment Calibre Weight of shell Ammo. MV (ft/sec) Range(yds) Year of adoption
18 pr Mk I QF 1.26 tons 3.3in 18.5 lb
18.5 lb
10.25 lb		 Shrapnel
HE
Star		 1615 6,525 1906
18 pr Mk II QF 1.26 tons 3.3in 18.5 lb
18.5 lb
10.25 lb
18 lb
17.2 lb		 Shrapnel
HE
Star
Smoke
Gas		 1615 6,525 1916
18 pr Mk III QF 1.46 tons 3.3in 18.5 lb
18.5 lb
10.25 lb
18 lb
17.2 lb		 Shrapnel
HE
Star
Smoke
Gas		 1640 9,300 1917
18 pr Mk IV QF 1.46 tons 3.3in 18.5 lb
18.5 lb
10.25 lb
18 lb
17.2 lb		 Shrapnel
HE
Star
Smoke
Gas		 1640 10,800 1918
18 pr Mk V QF 1.54 tons 3.3in 18.5 lb
18.5 lb
10.25 lb
18 lb
17.2 lb		 Shrapnel
HE
Star
Smoke
Gas		 1640 10,950 1920s
25 pr Mk 1 (18/25 pr) QF 1.46 tons 3.45in 25 lb
21.8 lb
20 lb
.
.
.
.		 HE
Smoke
AP
Star
Incendiary
Flare
Chemical		 1700 11,800
11,000
600-800
.
.
.
.		 1937
25 pr Mk II QF 1.75 tons 3.45in 25 lb
21.8 lb
20 lb
 
 
 
 		 HE
Smoke
AP
Star
Incendiary
Flare
Chemical		 1700 13,400
11,000
600-800
 
 
 
 		 1940
25 pr Mk III QF   3.45in 25 lb
21.8 lb
20 lb
 
 
 
 		 HE
Smoke
AP
Star
Incendiary
Flare
Chemical		 1700 13,400
11,000
600-800
 
 
 
 		 1943/44
75mm Ml QF 0.6 tons 2.95in 14.6 lb
 
 		 HE
HEAT
Smoke
 1250 9,525 1942/43
4.2in Mortar ML   4.2in 20 lb
 		 HE
Smoke		 - 4,369 1946
105mm pack howitzer
L 10 Al		 QF 1.25 tons 4.l3in 33 lb
 
 
 
 
 
 		 HE
HESH
HEAT
Smoke
Illuminating
Gas
Propaganda		 1350 10,800 1959
105mm light gun QF 1.74 tons 4.l3in 35 lb
 
 
 
 
 		 HE
HESH
Smoke
Illuminating
Target indicating
Anti-personnel		 - 18,400 1973

NOTES

1. In this table, the weight of the complete equipment is given. In the earlier tables gun weight was listed as this was normally an integral part of the gun designation. Weight behind the team included limber as well as the complete gun and carriage, and was important as guns were horse drawn. This factor is less important to-day with mechanical transport. What is more important is the weight of the complete equipment on its firing platform, as this weight is vital when helicopter movement and parachuting are considered.

2. Several charges were available in the case of the 25 pr and 105mm, so muzzle velocity will vary with each charge. MVs quoted are for the normal maximum charge used. The 25 pr firing charge super with increment in the anti-tank role had an MV of 2,000 ft/sec. The Italian 105mm pack howitzer had seven charges.

3. The 4,2in mortar was in use during World War 11, but by the infantry. It became a gunner weapon after the war.

4. Three types of anti-tank ammunition are listed AP (armour piercing) shot, HEAT (high explosive anti-tank), and HESH (high explosive squash head). AP shot was solid and came in various forms, capped, with discarding sabot etc. HEAT and HESH are explosive in their action. The former works on the hollow charge principle where energy is transformed into a powerful jet which penetrates the armour and delivers a stream of flame and hot gas into the tank. Britain accepted this principle for non-rotating projectiles such as the PIAT (Projector, infantry, anti-tank). HESH ammunition squashes against armour before detonation to blow off a large ‘scab’ within the tank.

5. ‘Illuminating’ is a better name for ‘Star’. Propaganda leaflets could also be packed in the 25 pr’s carrier shell, the name for the group including smoke, star, etc.

6. It may be of interest to the reader to compare this table with those printed in earlier issues, to compare the progress made in effectiveness of field artillery over 100 years. The 105mm light gun, the British Army’s latest, is included for comparative purposes.

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