The Quick Firing 25pdr

The 25pdr Gun-How on display with the Garrison has its origins in the Great War. It was in 1919 when plans were being made by the Royal Artillery Committee to make the next generation of field gun.  It was considered the best two field guns had been the 18 pdr gun, (still seen at parades and displays of the famous ‘K’ or King’s Troop of the Royal Horse Artillery) and the 4.5” howitzer.  The development of field artillery in Britain at this time was restricted through stringent budget cuts for the War Department, and post war political belief that the Army would not have to fight another major war for at least ten years. In addition there was a huge stock of artillery left in gun sheds around the country.

A committee was set up in 1919 to develop a new artillery piece that was to have the capability of gun and howitzer specification, to be able to fire at moving targets, projectiles to be easily man-handled, to achieve a maximum predicted range, to have a total weight of gun at 30cwts, allowing a six horse gun team to be its prime mover.
18 pdr 4.5 inch howitzer Vickers 105mm

          Click on photos for a better view

In 1924 the first attempts of a new gun, started with the design of a 99mm shell, thought to be an appropriate weight for handling and its destructive power. Although the results of test firing fell short of the specifications, the Ordnance Committee were asked to consider the design of a weapon with a range of 15,000 yds, but combing the gun-how combination role.  Between 1924-5 an 105mm howitzer was being made by Vickers for the Spanish Artillery, and could be mounted on the old 18 pdr carriages. It fell very short at 9,450 yds to the specification of 15,000 yds.

In 1931 Vickers produced a later version with extended barrel mounted on a new humped box trail which was tested by the RA on Salisbury plain, the results suggested a 3.7” calibre barrel, firing a 25 pound projectile might achieve the specifications set in 1919 for the new gun.  By 1933 three guns were in service with artillery regiments; the 13pdr (RHA) the 18pdr and 4.5” howitzer with field batteries. These First World War origin guns were now suffering from lack of range and explosive effect compared to the new guns being supplied to foreign artillery. This was compounded by the improvements of the new high-explosive projectiles which were best delivered on targets at a steep angle by howitzers. There was also the developing requirement of engaging moving armoured targets! Development continued in the early 1930’s surplus 18pdr carriages were used to mount the new barrels for testing, thus keeping costs down. The 3.7” barrel was too heavy and on firing was stressing the carriage, so a new barrel of 3.45” (87.6mm) was introduced, firing a 25pdr projectile and by 1934 the 25pdr. Mk. 1 (18/25) Gun / How was approved.

   
Mk 1 25pdr (18/25) A Mk 1 from the rear Mk 1 variant with split trails

The limitations placed on the old 18 pdr carriage, despite being fitted with pneumatic wheels to correspond with the newly introduced mechanical gun tractors and modification to the traversing and elevating gear, still limited the potential range of the gun - a new carriage was needed!  Designs for a carriage by Vickers and Carriage Design Department at Woolwich Arsenal explored many novel concepts, but no decision was made on which to accept. The 25 pdr Gun Howitzer MK I was approved on the 7th December 1937, so that production could begin, but still no carriage.  The design of the carriage trail - ‘split’ or ‘boxed trail’ - was finally overcome in the 1938 trials, where the ‘humped box trail’ mounted on a circular firing platform was adopted. This had proved to have superior handling qualities, including 360 degree traverse, despite limited lateral movement of the piece itself and became the accepted design.

The 25pdr MKI having been approved for production on December 7th 1937 had been delayed for production until the firing trials of 1938 and in that year only 78 gun barrels had been manufactured and no carriages at all.  Vickers, the main contractor for pre-war production had already prepared a box trail design in 1931 intended for a commercial howitzer.  The initial conversion of the 18/25 pdr gun howitzer, numbering some 1000 pieces had been distributed to the RA regiments by the outbreak of war in 1939 and was the main field artillery piece. During the withdraw from Dunkirk in 1940, the 25 pdr Mk1 was outnumbered and outranged by the German artillery, but proved highly effective in defensive actions. Over 704  25pdr Mk 1 were abandoned, many spiked and ammunition was destroyed.

   
Early Mk 2 without muzzle brake Mk 2 with muzzle brake Mk 3 narrower with a pivoting trail allowing higher elevation


The 25 pdr Mk. II with Mk. I carriage was introduced in the List of Changes on 29th February 1940. With the new carriage the gun could achieve a range of 13,400 yards (12,253m), using a supercharge cartridge.  With the outbreak of war, many companies in Great Britain and the Commonwealth helped in war production effort, including Australia and Canada, in fact it was the 8th Field Regiment of the Royal Canadian Artillery who was the first to be fully equipped with 25pdrs.  The gun was sturdy and rugged yet easy to operate and maintain. The calibrating sights, with a range cone, were simple to use and the associated command post procedures and gun drills were equally simple to perform.  Initially it had to function both as an anti-tank gun and field gun but by 1942 the introduction of the 6 pdr anti-tank gun, allowed the 25 pdr to revert to its primary field gun role.

While in the same year improved communications systems were introduced, the principle of concentrating artillery fire at regimental, divisional or army level was established. Fire from all available batteries could be brought down on a single target and the 25pdr with its traversing platform, was ideal for such engagements which required quick but major change bearings.  In June 1943 the 25pdr gun was upgraded back to an anti-tank role again with the fitting of a double baffle muzzle brake and weighted block over the breech to re-balance the fun and reduce the recoil when using the additional charge necessary for use when firing armour piercing (AP) shot.  The upper portion of the protective shield can be lowered, this allows the gun layer to use open sights at point blank range when engaging tanks for instance, it was in this position when coming in to action, to allow the layer to see the director when the gun was being aligned and also when travelling to give the tractor driver a clearer view to the rear.

More than 12,000 25pdr guns were made. It was phased out by 1967 (although the last round fired from a Regular Army 25pdr, was fired by 19 Field Regiment RA on April 1st 1975) but still used for training until the early 1980s. It was also used in the ceremonial role until very recently, when it was replaced by the light gun. The last twelve 25pdr gun–hows left the British army in 2004.