25-pounder Gun

The Ordnance, Quick Firing 25-pounder (or just "25-pounder" in short form, also seen as 25-pdr) was the main field piece of Canadian artillery units beginning in 1940. The 25-pounder was used in Field Regiments (in both towed, and later self-propelled configuration) in Canada and overseas, and was a popular weapon replaced primarily due to the desire to standardize ammunition throughout NATO. Canadian units used the weapon into the 1960s. The gun was noted for reliability, mobility and high rate of fire. Canadian soldiers last used the weapon in combat in the Korean War; other Commonwealth nations carried the weapon on inventory into the 21st Century. The last combat use of the 25-pounder by British troops was in Oman in 1972. The Regular Force in Canada fired their last 25-pounder round on 12 Dec 1956, and the Militia had ceased training on the gun by May 1959 when the last 45 guns on inventory were sold or transferred to museums.¹

Evolution   

The history of the Royal Canadian Artillery notes that

It has been said with some authority that the 25-pounder - the equipment which was to become the main weapon of Canadian field artillery in the Second World War - was the first piece of artillery to be developed logically from "the target backwards."²

In the political climate following the First World War prevailing in Canada and the United Kingdom, development of military weapons stagnated; only one new ordnance design - a 3.7-inch pack howitzer - made it from the drawing board to production in this period.

The development of field artillery proceeded slowly, progressing from the belief that the desired role of artillery in a major conflict would be suppression - forcing the enemy under cover to keep their heads down during friendly attacks, and on the defensive to destroy advancing enemy infantry or drive them to ground.

Debate about type and weight of projectile centred around the proposition that rapid fire was desirable; for manually operated field guns, this placed a limit on the "loading weight" of individual rounds, and weights of from 30 to 50 pounds were considered the maximum weight which gunners could reasonably be expected to maintain high and sustained rates of fire with. The actual projectile was thus restricted to between 20 and 30 pounds. These restrictions led to the use of "semi-fixed ammunition" with the 25-pounder.

Design

The goal of British artillery designers in the 1920s was to combine the best features of the war-tested 18-pounder Gun and the 4.5-inch howitzer, ideally having a heavier shell than the former, with longer range and higher velocity than the latter, but with a multiple charge system permitting the gun to do the jobs of both weapons. A final design was finally reached by 1935, with a 3.45-inch gun-howitzer firing a 25-pound shell, using three propelling charges.

The first guns were produced by removing 18-pounder barrels from their carriages in favour of the new gun barrel and breech, creating the "18/25-pounder" and being officially designated the "Ordnance, 3.45-inch." In metric, the gun measured 88mm - which would become a name closely associated with the famous German anti-aircraft and later dual purpose anti-aircraft/anti-tank gun of the Second World War. The designation did not stick, however, and sentiment won out in the designation being changed to the more traditional "25-pounder."

A new carriage was next designed, though the 18/25-pounders saw active service until after the French campaign ended in Jun 1940 in British and Canadian units. The new carriage was to be of split-trail design but users in field units in 1938 expressed a preference for a box-trail with firing platform allowing rapid traverse. The unique circular firing platform was put into production late in 1939, and the first of the new guns saw action in limited numbers in Norway in Apr 1940.

An unpopular add-on, at least to those who had to drive the guns, was an ammunition limber which connected to the gun and was towed between the gun tractor/truck and the gun itself.

18/25 Pounder Gun

Employment

The 25-pounder was the main gun used by Commonwealth divisions during the Second World War. An infantry division was authorised seventy two 25-pounders, with each of the division's three Field Regiments fielding 24 guns in three 8-gun batteries.

The gun was normally towed, with its limber, behind a 4x4 Field Artillery Tractor (FAT, also called a "Quad", short for "quadraped" and a reference to the 4-wheel drive capabilities of the tractor).

Self-Propelled versions of the 25-pounder were built after the success of the American M7 Priest; Canadian SP units used the Sexton, mounting the 25-pdr on a Canadian Ram tank chassis.

Effectiveness

The 25-pounder fired a small round by Second World War standards, as most armies employed weapons of 105mm size and larger in their divisional field artilleries.

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Variants

Ordnance, Quick Firing 25-pounder Mark I (QF 25-pdr Mk I)

The first 25-pounders were conversions of the 18 pdr and entered British service in the early 1930s. Often referred to as the 18/25-pdr, the majority of these guns were lost by the British Army in the early Norwegian Campaign.

Ordnance, Quick Firing 25-pounder Mark II (QF 25-pdr Mk II)

The Mark II, many of which were built by Canada in Sorel, Quebec, entered service with the Royal Canadian Artillery in Apr 1940. The Mark II featured the addition of a "super" charge to increase the gun's range to 13,400 yards (12,250 m), the power of which put extra stresses on the carriage. A muzzle brake was added to counteract this additional recoil; guns with this modification were known as the Mark 2/1. The distinctive brake is a well-known feature of the gun that makes it easily recognized.

Ordnance, Quick Firing 25-pounder Mark III (QF 25-pdr Mk III)

The Mk III gun was a Mk II with a modified receiver to prevent the rounds from slipping back out when loading at high angles. Mark III guns with the muzzle brake retrofitted were designated Mark III/1.

Ordnance, Quick Firing 25-pounder Mark IV (QF 25-pdr Mk IV)

The Mk IV were new production guns of Mk III/1 configuration (ie with the modified receiver and muzzle brake).

Carriages

Two variant carriages were developed for this gun; the Mark II Carriage was developed for easier towing, and the Mark III Carriage included a hinge to allow the gun to be fired at much higher angles. Neither proved very reliable and were not widely used.

With the introduction of dedicated anti-tank guns, the single-trail design was no longer considered important, and the Mark 5 used a split-trail design with a much wider angle of traverse. The Australians developed a "cut down" version on a lighter mounting as the 25 Pounder Short Mark I.

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Ammunition

Types

As discussed above, the 25-pounder used semi-fixed ammunition. There were three different types of propellant charge, called Charge I, Charge II, and Charge III which differed in the amount of propellant used. The bags were colour coded and loaded seperately, placed inside a brass cartridge case fitted with a primer in the base. Muzzle velocity and range were affected by these differences.

• Charge 1 (red): 650 fps (feet per second)

• Charge 2 (red and white): 975 fps

• Charge 3 (red, white and blue): 1,450 fps

Additionally, "Supercharge" - an additional propellant bundle - could be added to Charge 3 to increase the range even further.

Ranges were:

• Charge 1: 3,566m

• Charge 2: 7,132m

• Charge 3: 10,790m

• Supercharge: 12,253m

The weapon fired the following types of ammunition during its service life:

• armour piercing

• high explosive

• white smoke

• coloured smoke

• illumination

• incendiary

• propaganda (leaflets)

• radar echo

• squash-head shells

A hollow charge shell was developed but never issued. ³

Designations for shells used included:

• Smoke Mark ID BE (Base Ejection)

• High Explosive Mark ID

• Armour Piercing Mark 1T (steel shot with a tracer)

The HE round could be used with a variety of fuzes, all of which served different purposes, including the 115E, 117, 117B, 119, 119B, 213, 222, 231, 232, T97E6 and T97E9.

Projectiles were painted the following colours:

• High explosive: buff

• Smoke: green

• Armour Piercing: black

HE rounds normally contained Amatol, though other explosives such as TNT and RDX were sometimes used instead.

Other markings on the projectiles included coloured rings:

• Head

• Red: shell was filled

• Ring of red crosses: filled with material suitable for tropical conditions (similar to the same markings on the 36M Grenade)

• Black over red: contained exploders suitable for powder-filled fuzes

• White: armour-piercing shot

• Body

• Green: filled with TNT or Amatol

• Black over black: HE practice round

• Black: Drill round

• Yellow: Practice projectile

Korean War Ammunition

During the Korean War, Canadians again used the 25-pounder, with the addition of proximity fuzed shells (also known as Variable Time (VT) shells) which were set to explode above the ground rather than exploding on direct contact with the ground itself, increasing its lethality.

Ammunition used in the Korean War included High Explosive (HE), which were the majority of rounds fired. Doctrine provided the following quantities for each gun, though in practice more could be stockpiled at each gun as needed for for specific operational requirements):

• HE – 144 rounds

• White smoke (base ejecting) – 16 rounds

• Coloured Smoke (base ejecting) – 8 rounds

• Illumination – 8 rounds

• Anti-tank – 2 rounds

According to the Royal Canadian Artillery Museum:

Illuminating rounds were rarely used. The main source of illumination was flares dropped from C-47 Dakota aircraft. No white phosphorous (WP) rounds were used by the Canadians in Korea. Coloured smoke was used to indicate specific targets or timings. In addition, a further 68 rounds (proportionately mixed) were held on ammunition trucks in the A Echelon of the Regiment. All other ammunition was held at a Divisional Ammunition Point (AP). “No. 25 Cdn Inf Bde Ordnance Coy” and “Canadian Army Ordnance Elements, First (Commonwealth) Division” managed the ammunition within the Canadian Brigade and within the Division respectively. Canadian sources and units were responsible to re-stock a portion of the AP holdings. Transport Companies of the RCASC moved the ammunition in theatre. Ammunition from the AP was issued to whatever unit from the Divisional Artillery required it (i.e. it was issued based upon amounts held not on a national basis). Much of the Canadian ammunition was actually recovered from Hong Kong harbour, where it had been sunk (during the Second World War.⁴

The following fuzes were used:

• Fuze 119 – an instantaneous fuze for HE to cause impact bursts on the ground. It could also be fired with a cap over the end of the fuze that caused a slight delay in detonation to improve performance against fortifications and dug in troops;

• Fuze 213/213C – these were mechanical time (MT) fuzes used to produce HE airbursts. The fuzes would also point detonate if they hit the ground. The 213 was very sensitive and sometimes detonated in flight due to hitting raindrops. The 213C was less sensitive;

• a variable time (VT) fuze (model number unknown) that employed a small radar to cause HE airbursts. The radar gave a more constant height of burst than MT the fuze, but would sometimes detonate too high in very rough terrain; and

• Fuze 221/221B– a mechanical time fuse without a point detonating capacity used to cause smoke and illumination rounds to function.

In Jul 1953, Canadian production of 25-pounder ammunition ceased, in anticipation of the adoption of the C1 105mm Howitzer.⁵

Trailer

Ammunition was carred in the No. 27 Trailer, a variant of the prewar No. 24 trailer used in the British Army before 1939. Ammunition trailers (also called "limbers") were hooked directly to the gun tractor, with the gun hooked to the trailer for road moves. Two ammunition trailers could also be towed in lieu of a trailer and gun combination. In addition to ammunition (the trailer was designed to carry 32 rounds, stacked in sliding trays), the No. 27 trailer also carried tools and spares, and could also have the circular firing platform stowed on top for transport. Typical tools carried included axes, crowbars, a projectile erector, handspikes, jack, spade, drag ropes and an illuminated aiming point with post spring and cover.⁶

Stores

Commonly issued tools for each gun included the following:⁷

• Adaptors

• Air pipe No. 2

• Pumps (used to recharge the recuperator as needed with either air or liquid, two pumps were provided with each gun.) Carried in a socket on the trail.

• No. 1 pump

• No.14 Illuminating apparatus for an aiming point - used for night firing to establish a reference point to locate bearing. Also known as a Gun Aiming Point (GAP)

• Sights No. 5

• No. 7 gun pull-back

• Quick Release Attachment No. 3

• Boxes, charging pumps

• Spade Platform No. 2

• Cap Sponge No. 6

• Cleaner Piasaba No. 18

• Cleaner Wool No. 1

• Field Clinometer

• Covers - canvas covers for breech, muzzle, sight, and an overall gun cover for use when the gun was being towed or transported

• Ejector projectile - a tool used to force a stuck projectile back down towards the breech; designed so as not to apply pressure directly on the fuze.

• Pressure guages

• Striker Protusion No. 16

• Handspike 25-pounder

• Cartridge holder 25-pounder QF

• Keys - for use with ammunition

• No. 34 Key (cartridge primer)

• No. 119 Key (for inserting and removing fuzes)

• No. 120 Key (for setting fuzes)

• No. 121 Key (for inserting and removing 2-inch percussion fuzes)

• No. 139 Key (for setting the No. 210 time fuze)

• Fuze Indicator No. 20

• 2.5-ton lifting jack

• Pulling jack No. 2

• Key muzzle velocity corrector scale reader

• Removing jammed QF cartride No. 1

• Cocking lanyard No. 7

• Pipe, charging No. 2

• Plane testing dial sight carrier No. 7 or No.7C Dial Sight

• Platform No. 9

• Posts, aiming crosshead No. 1

• Rammer QF 25-pdr

• Reservoir compressed air 5.5" diameter

• Stop running back - a metal bracket fitted to the rear of the breech assembly to prevent it sliding off of the cradle

• Telescope Sighting No. 29

• Spanners and special implements

Tractors

During the Second World War, the 25-pounder was most normally towed by a special purpose gun tractor derived from the Canadian Military Pattern 15-cwt truck. In Korea, guns were towed by US-built 2-1/2 ton Trucks, and from the mid 1950s the M135 Truck.

Notes

1. Knight, Doug. The 25-pounder in Canadian Service, Service Publications, 2004. ISBN 1894581261 p.22

2. Nicholson, G. The Gunners of Canada, Volume II, Appendix H, p.669 - the quote is attributed to General G.G. Simonds.

3. Illustrated Encyclopedia of 20th Century Weapons and Warfare, Volume 9, p.1000

4. Correspondence with RCA Museum.

5. Knight. Ibid. p.22

6. Henry, Chris. The 25-pounder Field Gun 1939-72 (Osprey Publishing Inc., Botley, Oxford, UK, 2002) ISBN 1841763500

7. Ibid, pp.16-18