25 POUNDER GUN (HOWITZER)


25 Pdr located at Naracoorte S.A.


Images by Patrick Sprau


Introduction

The 25-pounder was the outcome of the experience of nearly 40 years of war and peace. The lessons of the South African War, at the turn of the century, led the British authorities to develop the 18-pounder field gun and the 4.5-inch howitzer, both of which gave splendid service with the Canadian and British armies in the First World War. During the inter-war years it was decided that a new gun should be designed which would be capable of providing both the high angle fire of a howitzer and the flat trajectory fire of a field gun. Theoretical studies indicated that such a gun should have a calibre in the order of four inches and fire a shell weighing about 30 pounds. The financial restrictions resulting from the economic depression of the 1930's made it imperative that use should be made of the existing stock of 18-pounder guns. By relining these guns, using modem technology, it was possible to increase their calibre to permit them to fire a heavier shell. The original 25-pounders were thus, in reality, converted 18-pounders mounted on 18-pounder carriages.

In order to provide the ballistic characteristics required for both the howitzer and field gun roles, the 25-pounder was originally provided with three different propellant charges. To permit the adjustment of the charge as required to engage a specific target, the shell and the cartridge case were loaded separately, in contrast to the fixed ammunition of the 18-pounder gun. Experience showed that the flexibility of the 25-pounder could be further improved if an even greater choice of charges was provided. This need was met by the introduction of two small propellant increments which could be used to produce muzzle velocities between those of the three main charges.

There was also an operational need to increase the maximum range beyond the 11,500 yards obtainable with Charge 3. To meet this requirement a super charge was developed to give a range of 13,400 yards. This charge naturally produced extra stresses on the carriage and muzzle brakes were introduced to relieve this problem.

While the standard projectile of the 25-pounder was a high explosive Technical Details shell, numerous types of carrier shells were developed in response to operational needs. These included smoke, flare and star shells and even a shell to discharge leaflets over enemy positions.

In addition to its functions as both a howitzer and a traditional field gun, the 25-pounder had a very potent anti-tank capability. To facilitate this function, advantage was taken of an invention which dated back to the end of the First World War. A circular platform was carried under the trail which could be dropped on the ground, allowing rapid all round traverse for anti-tank firing. (See alternate photo above)

During the course of its service life the 25-pounder gun was mounted on numerous designs of carriage. Many of the converted 18-pounders were lost at Dunkirk in 1940 and were replaced with carriages designed for the 25-pounder. The two which became best known were the Mark 4 and the Mark 5. The former had two box shaped side brackets connected at front and rear, while the latter had a split trail which permitted extended traverse. 

Standard projectile

HE Shell Mk. ID S/L
Fuse No. 117 or 119
Weight - 25 Ibs.

Range Table
Muzzle Velocities

Charge 1: 650 ft. per sec.
Charge 2: 975 ft. per sec.
Charge 3: 1,450 ft. per sec.

Ordnance - Steel:

Weight with breech mechanism 8 cwt. 3 qtrs (444 kgs)
Length - 96.72 inches
Calibre - 3.45 inches
Chamber capacity - 151 cu. inches
Polygroove rifling - 1 turn in 20 calibres (69 ins)

Manufacturer

Ordnance

Country of Origin

UK

Calibre

3.45inch (87.6mm)

Length (metres)

2.40

Wheel Base width (metres)

1.79

Weight (kg)

1,800 in action

Ammunition

25lb (11.33kg) shell. (HE, Armour-piercing, Shot, Smoke, Illuminating)

Range (metres)

12,253

Rate of Fire (rounds per minute)

10

Information sourced with permission from the Digger History website.

The images


 


 

This site is owned by David Harvey

All material is Copyright © 2003-2016 and may only be reproduced for personal use.
Please contact the Editor for permission to use any material on this site for any purpose other than private use.

Contact: editor@aussiemodeller.com.au