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25 Pounder Field Gun PDF Print E-mail
Written by David Boyd   
Thursday, 01 January 2009 14:22

The 25 Pounder Field Gun

25 Pounder Field Gun    25 Pounder Field Gun

In May 1934 the General Staff issued a specification for a gun/howitzer to take the place of old weapons, the weapon was to...

  • Have a weight in action of 30 cwt
  • Fire a projectile weighting between 20 and 25lb
  • Range at least 12,000 yards
  • Rate of fire of 8 rounds per minute
  • Self protection desirable but not to unduly affect the design
  • Road performance of 25mph essential
  • Mass production of the weapon was to use materials and plants readily available commercially.

The specification also included the convention of 18 Pounder guns for three reasons.

  • The desire to obtain homogeneity for ammunition at the earliest date
  • Large stocks of 18pdrs were available and later marks had a heavier carriage capable of taking a more powerful gun
  • It had been decided to mechanize all field artillery and the additional carriage modifications were not serious

Trials of 18pdr, 22pdr and 25pdr projectiles were carried out and in April 1935 the 25pdr shell was decided upon, after this it was also decided the effective range of the equipment should be 15,000 yards. It was later pointed out that a weapon with this range would be incompatible with a carriage of 30 cwt due to the recoil stress involved, a shell capable of travelling this distance but with inferior lethal performance was proposed but rejected. A range of 13,500 yards was accepted by March 1936, development of the 25 pdr gun then proceeded.

Both box trail and split trail carriages were investigated in 1937 and the split trial type was chosen, pilot models were completed in 1938 and were found to exceed the specified weight considerably, it was then decided to revert to the box trail carriage, trails were arranged in October 1938 which were satisfactory, production drawings of the box trail pattern carriage were adapted and the necessary production capacity arranged.

The 18pdr was chosen for modification in December 1934, preliminary trials in the autumn of 1935 were successful, a battery of 18/25 pdr were ordered for intensive user trails. The modification of the gun consisted of lining it to 3.45" calibre and the carriage was pneumatised, a new buffer value and new sighting gear were also provided. The gun design was firm by the summer of 1936 and the carriage by the spring of 1938.

There were two marks of the Quick Firing 25pdr. The Mk I was the converted 18pdr, the Mk II new 25pdrs. The two Marks were separate weapons and the only common qualities were the ammunition and the trailer, the Mk I could not fire the super-charge and thus was limited to 11,500 yards.

25 Pounder gun details

  Mk I (18/25pdr) Mk II
Weight (with breech mechanism) 991 lb 1,000 lb
Total Length 96.725 inches 97.473 inches
Bore, Calibre 3.45 inches 3.45 inches
Bore, Length 92.365 inches 92.375 inches
Rifling System Polygroove, plain section Polygroove, plain section
Firing Mechanism Percussion Percussion
Projectile weight (approx) 25lb 25lb
Muzzle velocity (normal) 1486fps 1486fps
Muzzle velocity (supercharge) - 1747fps
Max Range (normal) 11,500 yards 11,500 yards
Max Ranger (supercharge) - 13,400 yards

 25 Pounder carriage details

  Mk II (new) Mk I (converted)
Weight (total equipment) 3,970 lb 3,580 lb
Height, top of shield 5'-6.75" 6'-3"
Length including trailer 25'-10.75" 26'-8"
Max width 6'-11.5" 6'-9.25"
Max elevation 40 degrees 37 degrees, 37 mins
Max depression 5 5
Transverse L,R without platform 4 degrees 4 degrees 30 mins

Ammunition

The designs for High Explosive and Smoke shells were available in 1937, for anti tank use an armour piercing tip was designed to replace the fuze in HE. Design of armour piercing ammunition for the 25 pounder was not cleared until the winter of 1939/1940. Investigations into chemical shells began in 1937 and specifications were made available in 1939. To improve the performance of the 25 pounder AP round against face hardened armour a cap was provided, it was then realised that the cap would only help at velocities higher than the guns muzzle velocity so it was never used.

25 Pounder Projectiles

Nature Mark Fuze Length (excluding fuze plug and external tracer socket Body Diameter Driving Band Diameter Empty Weight Filling Weight Burster Weight Fuze Weight Total Weight
High Explosive ID 117,117c,119,222 13.84" 3.44" 3.56" 20.68lb 1.82lb   2.5lb 25lb
Smoke, Streamline ID 221 13.03" 3.44" 3.56" 14.58lb 5.02lb 0.1lb 2.13lb 21.81lb
  IID 221 13.03" 3.44" 3.56" 14.55lb 5.02lb 0.1lb 2.13lb 21.78lb
  IIID 221 13.03" 3.44" 3.56" 14.53lb 5.02lb 0.1lb 2.13lb 21.77lb
  IVD 221 13.03" 3.44" 3.56" 14.66lb 5.02lb 0.1lb 2.13lb 21.9lb
  VD 221 11.71" 3.44" 3.56" 14.49lb 5.02lb 0.1lb 2.13lb 21.73lb
  VID 221 11.71" 3.44" 3.56" 14.48lb 5.02lb 0.1lb 2.13lb 21.71lb
Smoke VIIB 221 11.71" 3.44" 3.56" 14.52lb 5.02lb 0.1lb 2.13lb 21.86lb
  IA 220 14.9" 3.44" 3.56" 16.16lb 6.6lb 0.1lb 2.23lb 25.08lb
Armour piercing shot IT  - 9.33" 3.44" 3.56" 19.83lb - - - 20lb
  IIT 9.43" 3.44" 3.56" 19.83lb - - - 20lb
  IIIT  - 9.31" 3.44" 3.56" 19.99lb - - - 20lb
  VIT  - 9.28" 3.44" 3.56" 19.96lb - - - 20lb
  VIIIT  - 9.28" 3.44" 3.56" 19.96lb - - - 20lb
Armour piercing shot, capped VIIT  - 9.18" 3.44" 3.56" 19.96lb - - - 20lb

Production and conversion of 25 Pounder guns per year (UK only) * gun figures are not listed from June 1942 as they exceed carriage production

  Pre war Sep-Dec 1939 1940 1941 1942 1943 1944 1945 (May)
18 pdr to 25 pdr gun conversion 828 186 399 55 - - - -
18 pdr to 25 pdr liner conversion 799 197 438 214 1 - - -
18 pdr to pnue tyres 903 520 583 46 - - - -
18 pdr to 25 pdr Carriages 603 142 570 46 4 - - -
25 pdr Guns 78 111 776 4,427 1,764* NF NF NF
25 pdr Carriages - - 1,359 3,074 3,299 2,017 408 243
25 pdr Trailers 1,407 1,245 4,630 2,380 6,419 3,461 NF NF
25 pdr Carriages (baby) - - - - - - 2 109

Production of 25 Pounder ammunition per year (Filled only, UK only)

  Pre war Sep-Dec 1939 1940 1941 1942 1943 1944 1945 (May)
25 pdr HE 1,177,803 2,626,895 3,836,826 9,755,200 15,011,000 7,351,000 6,153,000 5,859,000
25 pdr Smoke 152,241 126,359 1,000,205 1,178,600 - 60,000 - -
25 pdr Col. Smoke - - - - - - 155,000 133,000
25 pdr Night Marker - - - - - - 15,000 42,000
25 pdr AP - - 37,210 462,800 1,512,000 440,000 - -
25 pdr Chemical - - - 195,000 2,043,000 928,000 475,000 -
25 pdr Cartridges 1,845,347 386,097 8,879,653 10,140,000 12,398,000 5,458,000 4,822,000 4,946,000
25 pdr Cartridges (Super) - - 510,726 586,000 3,398,000 895,000 - -

Production of 18 Pounder ammunition per year (Filled only, UK only) *Data missing for several months, HE figures may include some smoke also

  1940 1941 1942
18 pdr HE 819,422 417,200* -
18 pdr Smoke 96,703 72,000* -
18 pdr Shrap 11,140 - -
18 pdr AP 9,316 62,600 43,000

 

Sources - 

Last Updated on Thursday, 01 January 2009 14:23
 

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