With the adoption of the more powerful smokeless propellant Cordite in 1892, the 12-Pdr BL 7 Cwt Gun that entered service in 1883 was modified to fire a heavier shell becoming the 15-Pdr BL Gun in 1895 with BL standing for breech loading. However, the decision was taken that the 15-pdr field gun would only fire shrapnel shells (and case shot) and a field howitzer would be used to fire explosive common shells. The reason for this was that the black powder bursting charge in common shells at this time tended to break the shell into a small number of large pieces that were not very effective against infantry in the open. Nevertheless, plunging common shells fired from howitzers were effective against infantry behind cover and in trenches. In contrast, shrapnel shells fired by field guns were effective against infantry in the open but their flat trajectories made them ineffective against infantry behind cover. Therefore, it was concluded that the 15-pdr firing shrapnel shells would be the perfect complement to a howitzer firing common shells. The 5-Inch BL Howitzer was therefore developed to accompany the 15-pdr in the field and also entered service in 1895. Ironically, even with the adoption of high explosive Lyddite common shells a few years later, field guns were still limited to fire shrapnel shells right up to the start of WW1.
The 5-inch howitzer was developed at a time when field gun technology was rapidly changing especially with the introduction of recoil systems. Although the 5-inch howitzer incorporated a rudimentary hydro-spring recoil system, this provided only 5.5 inches of travel and was therefore of limited effectiveness. The howitzer also used a very short barrel (9 calibres) and, during the 2nd Boer War (1899-1902), its range was found to be inadequate. It was eventually replaced by the Ordnance QF 4.5-Inch Howitzer in 1908 but it continued to be used by the Territorial Force up to the early part of WW1 and was used at Gallipoli, in particular, in 1915.
Gun Design
The gun was of 5-inch calibre and 9.8 calibres in length. It was made of steel and consisted of a rifled A-tube over which was shrunk a B-tube. A jacket was then shrunk over the rear two thirds of the B-tube with the assembly secured longitudinally by shoulders on the A- and B-tubes. A breech bush was screwed into the rear of both the B-tube and jacket with a breech ring for attaching the gun via lugs to the hydraulic buffers screwed over the rear of the jacket. The jacket was fitted with longitudinal projections to act as guides for the gun during recoil in the carriage cradle. At the front of the jacket, there were seatings provided for the foresight brackets with a plane in between for a clinometer.
The gun employed a de Bange interrupted threaded breech screw with a mushroom shaped axial T-vent projecting from the front of it with a fire proof seal behind the head. When the propellant ignited, the combustion chamber pressure forced the T-vent backwards slightly compressing the seal and forcing it outwards against the rear of the chamber thereby sealing it. The breech was unlocked by pulling up on the central lever and then rotating the breech plug through 60 degrees after which it could be pulled backwards relative to its hinged carrier and then swung out of the way to the right to expose the breech. The gun used an axial vent in the breech screw into which a friction tube was inserted to fire a cartridge.
Carriage Design
The carriage consisted of two side brackets, a trail eye, a cradle with hydraulic buffers and running out springs, elevating gear, shoe brakes, an axletree with 2nd-class arms, and two 5 foot diameter field wheels. The side brackets were of steel plate connected by top and bottom plates, transoms and a trail eye. Bearings were formed in the upper parts of the brackets to take the trunnion arms of the cradle. The cradle was held in position by cap squares which were hinged at their lower ends to the side brackets and secured at their upper ends by keys. A hole was cut in the right bracket for the lanyard to pass through when firing at extreme angles of elevation.
The trail eye was of wrought iron with the eye being fitted with a piece of hard steel. The cradle was a steel casting with trunnion arms to pivot it to the carriage brackets. It had an opening in the centre recessed at each side in which the howitzer slid on recoil and it had three cylindrical openings on each side; the centre one for a hydraulic buffer and the upper and lower ones for the running out springs. On the upper part of the cradle, a plane was cut for the clinometer. A line of white paint was marked on the right side of the cradle (excepting those in field batteries) in such a position that when the line was opposite the bracket of the carriage, the howitzer was in the loading position.
The elevating gear was supported in brackets that were attached to the right side of the trail and consisted of a screw, hand wheel with an oscillating bearing and case, and a connecting lever. It was actuated by the hand wheel that transmitted motion to the lever fixed to the cradle trunnion. When travelling, the hand wheel was strapped to a staple on the trail. A clamping arrangement attached to the right side of the trail was actuated by a lever that moved a jamming screw that clamped an arc against the inner face of the carriage bracket thus securing the cradle in any required position.
The brake consisted of two drag shoes suspended under the wheels by chains fixed to the axletree and to drag washers on the outside of the wheel axles. They were also held in position by chains attached to the rear of the trail. When not in use, the shoes and outer chains were hung on hooks fixed to the rear of the axletree.
The carriage was furnished with locking plates and fitted to carry a leather box (containing 1 claw hammer, 1 pair of pincers, 1 McMahon spanner, 1 breech brush, 2 hydraulic buffer spanners, No. 77 and 98, and 1 spanner filling plug, No. 79), a piasaba brush and stave-end, a traversing handspike No. 1, 2 aiming posts, a No. 9 oil can, a fuze key in a pocket, 2 water buckets, a tube pocket, a rimmer vent T, a rod vent, and a bit vent.
Limbers
The gun was towed by 6 horses behind a two wheel limber (below right) mounting a wooden ammunition box that opened at the rear via an upper and lower hinged cover. The ammunition box was divided into 4 tiers and carried 16 common shells, 16 cartridges, 16 fuzes together with other spares and accessories including a small and large clinometer. The Mk II limber was similar but with the ammunition box divided into 3 tiers and was fitted with boards at the front and back to allow 4 men to be seated on the limber.
The ammunition wagon needed to be towed behind a similar limber and mounted an ammunition box similar to that on the limber. The ammunition carried 16 common shells, 16 cartridges and 16 fuzes. The Mk II wagon ammunition box was in two portions and made to open both to the front and rear. Each portion had 3 tiers and held the same amount of ammunition and fuzes as the Mk I box.
Recoil System
Each side of the cradle housed a hydraulic buffer in the middle and two recuperators or running out springs above and below. The hydraulic buffer cylinder was filled with oil and contained a piston on the end of a rod bolted to the breech ring. When the gun recoiled, the buffer cylinder remained stationary fixed to the cradle while the piston was pulled backwards forcing oil in the rear of the cylinder to flow past the space around the outside of the piston. The cylinder was slightly tapered to the rear to reduce the flow space as the gun recoiled to maintain a constant retarding pressure inside the cylinder. In front of the piston was a short control rod that entered the oil filled channel in the front plug of the cylinder in order to cushion the final run out of the gun.
The running out springs were housed in cylinders and contained between the rear wall and a flange on the front end of a rod bolted to the breech ring. As the gun recoiled, the flanges compressed the springs against the rear of the cylinders and, after the recoil finished, returned the gun to battery. The recoil system only provided 5.5 inches of movement and, although it cushioned the initial shock of firing, did very little to absorb the recoil of the gun and prevent the carriage recoiling backwards.
Crew Detachment
The 5-Inch BL Howitzer was normally operated by a detachment of 9 men whose duties were:
No 1: Commanded, attended to the handspike, rammed home, lifted at the handspike in running up or back and in traversing.
No. 2: Attended to the brake and vent, fired, and manned a wheel.
No. 3: Attended to the brake and breech, received a round of ammunition from No. 6 or No. 7, uncapped the fuze or removed the safety pin, loaded and manned a wheel.
No. 4: Placed aiming posts, layed, and attended to the jamming gear, sights and clinometer. Brought the howitzer into a convenient position for loading and clamped the sights at the elevation and deflection ordered.
No. 5 : Fuzed shells and supplied No. 6 or No. 7 with ammunition.
No. 6: Supplied No. 3 with ammunition, helped in running up, returned empty cartridge tins and assisted No. 5.
No. 7: Performed the same duties as No. 6.
No. 8: Unhooked the wheel horses, supplied ammunition to the howitzer of their section which is not covered by the wagon and assisted in running up.
No. 9: Performed the same duties as No. 8.
When travelling, the No. 1 rode on his horse, the Nos. 2 , 3, 4 & 5 sat on the gun limber with Nos. 4 & 5 in front. The No. 6 & 7 sat on the wagon liner and the No. 8 & 9 sat on the wagon body.
Gun Loading
On the order from the No. 1, the No. 5 issued the ammunition ordered to No. 6 or No. 7. The No. 6 or No. 7 received the ammunition from No. 5, placing the cartridge under their left arm, carrying the shell by the carrying strap with the base of the shell to the front, handed them to No. 3 and assisted to run up, after which, they returned to the wagon or limber. At the first order to load, two rounds were brought up to the howitzer by No. 6 and No.7, and No.6 returned to the wagon or limber as soon as he has handed his round to No. 3 with No. 7 remaining ready to supply his round. The cartridges of the following rounds were sent up in their tins. Ammunition was first taken first from the rear of the wagon body and then from the front, the ammunition in the limbers being left to the last. The No. 3 uncapped the fuze or removed the safety pin and placed the shell in the bore. The No. 1 as soon as he saw No. 3 ready to load, took the handspike and, placing the copper-shod end against the shell, rammed it gently home. Then, keeping the handspike against the shell, he applied his whole force to ensure it being properly home. He then stood back and replaced the handspike in the socket. The No. 3 then placed the cartridge in the chamber (rings to the front), closed the breech, and held up the cam lever, whilst No. 2 inserted a friction tube and attached his lanyard. On the order from No. 1, the No. 2 fired the gun.
Sights
The elevation was originally set (before the introduction of the No. 3 dial sight) on the howitzer for shorter ranges using the tangent sights described below but, more accurate settings were achieved using a field clinometer mounted on the plane on the front of the gun between the foresight brackets. Range tables would have been used to determine the quadrant elevation required for a particular range.
The howitzer was fitted with cross-bar sights on each side of the gun. The fore and rear sights were very similar in design to enable both front and reverse laying of the gun. Reverse laying was used in the early days of the gun before dial sights were introduced for indirect laying and enabled the gun to be laid using aiming posts set up behind the howitzer.
The rear cross-bar sights were fitted into sockets on either side of the breech ring. They were provided with a vertical bar graduated from 0-10 degrees adjusted using a clamp and a reversible cross-bar graduated from 0-6 degrees in deflection. A sliding leaf was mounted on the cross-bar with a notch in it for forward laying and cross wires for reverse laying. By reversing the cross-bar, the sight could be used to provide both left or right deflections.
The fore sights were fitted to the brackets on the front part of the gun and were fitted with a half cross-bar with a moveable leaf similar to the back sights. The cross-bar was not reversible and so the right-hand sight only provided right deflection adjustment and the left-hand sight only provided left deflection, both from 0-6 degrees. The fore sights had a point for use in forward laying and a notch and key hole for reverse laying.
The cross-bar sights had to be specially designed to survive the recoil of the gun since they were attached to it.
From about 1906, the howitzer was also fitted with a No. 1 dial sight for indirect laying that was changed to a No. 3 dial sight shown below around 1909. In indirect gun laying, the required target bearing was defined by a plotting officer relative to an aiming point set up for the gun. This could be a suitable feature on the landscape identified on a map or it could be one or two aiming posts set up in the ground some distance from the gun.
The No. 3 Mk II dial sight was mounted on either side of the rear of the cradle in the sockets provided and consisted of a sighting tube mounted on a turntable marked in degrees from 0 – 180 degrees in either direction with a vernier to allow reading to 10 minutes. The sighting tube had a small eye hole at the rear and cross-wires at the front but also had open sights on top.
The sight mount was reciprocating and allowed the sight to be tilted sideways to compensate for the carriage wheels and gun trunnions not being level as was the norm. This was achieved using the cross-levelling screw and the cross-level bubble. The mechanism was also provided with a curved scale graduated from 0 to 15 to the right and left to indicate deflection. The amount of deflection of each scale division varied with elevation angle from 1.25 minutes at 5 degrees elevation to 10 minutes at 45 degs elevation.
The quadrant elevation required on the howitzer could be set using the range drum graduated from 0 to 45 degrees with divisions of 5 minutes. Once the quadrant elevation was set on the sight, the howitzer was elevated until the longitudinal bubble was level.
Ammunition
The 5-inch howitzer used bagged cartridges with a length of 3.2 inches. Each contained a core charge of Cordite and allowed up to 3 rings of additional Cordite to be added giving different muzzle velocities and ranges: core – 402 fps & 1,500 yds; core + 1 ring – 5566 fps & 2,600 yds; core + 2 rings – 670 fps & 3,600 yds; core + 3 rings – 782 fps & 4,900 yds. RFG powder was sewn into compartments in the base of the cartridge to be ignited by the flash from a T-tube.
The 5-inch howitzer fired four types of projectile: common shells, shrapnel shells, case shot and star shells with the first 3 weighing 50 lb and the latter 30 lb. The common shells were struck with a 2 CRH (calibre radius head) and were originally filled with a bursting charge of 3 lb 3 oz of P & FG black powder and made from cast iron but, by the time of the 2nd Boer War (1899), they were also filled with up to 9 lb 15 oz of Lyddite in Mk III form and made from forged steel. The common shells were originally fitted with a No. 1 or No. 3 direct action fuze and briefly with a No. 4 Graze fuze.
The shrapnel shells were made from forged steel and contained, originally, 368 mixed metal balls fixed in resin. When the time fuze ignited, the flash passed down to the ventral tube to explode the bursting charge in the base. This then blew the metal balls and nose of shell out of the front to spray the ground ahead of the burst with shrapnel balls. The No. 54 Time & Percussion Fuze was originally used with a maximum time delay of approximately 16 seconds limiting the maximum range for shrapnel to 3,400 yds. To increase the maximum range for shrapnel to 4,900 yds, the No. 62 time & percussion fuze was used with a maximum delay of 32 seconds.
The case shot was effectively a tin can filled with about 185 x 2 oz sand shot that was sprayed out of the muzzle of the howitzer when the cartridge was fired and was intended for anti-personnel use at close range. The star shell was filled with 8 stars in two tiers and set off by a No. 24 or 25 time fuze. The flash from the fuze passed down the central tube pieced by fire holes that ignited the stars. The flash also set off the black powder bursting charge in the base that then ejected the contents out of the front of the shell.
5-Inch BL Howitzer Specifications
- Length: 9 ft 1 in
- Wheel Track: 5 ft 2 in
- Wheels: 5 ft
- Weight of Gun & Carriage: 23 cwt 3 qr 13 lb
- Weight of Carriage & Limber: 46 cwt 2 qr 8 lb
- Calibre: 5 in
- Length of Gun: 49 in (9.8 calibres)
- Weight of Gun: 9 cwt 2 qr 13 lb
- Muzzle Velocity: 782 fps (core + 3 rings)
- Maximum Range: 4,900 yd (core + 3 rings)
- Trail: Box section
- Recoil System: Hydro-spring with 5.5 in of recoil
- Rifling: Polygroove hook section
- Length of Rifling: 36.8 in
- Twist: 1 turn in 28 cal
- Grooves: 20
- Firing Method: Friction T- tube
- Elevation: -5° to +45°
- Traverse: Fixed traverse on trail
