The Mountain Gun developed from warfare in Afghanstan and the frontier in northwest India. Fighting against irregular troops and tribesmen presented a unique challenge to protect columns traveling in hill country. Regular artillery couldn't be dragged up mountains easily, so smaller guns were developed for mobility in mountainous areas. One such gun was the Screw Gun, the first to have a barrel broken down into 2 parts. This invention was to change British tactics in India and Afghanistan.
The Screw Gun was the brainchild of Colonel Cecil Brook le Mesurier of the Royal Artillery in 1877. His proposal was to break the gun down into parts to be carried by pack mules. The maximum practical load at the time for a mule was 200 pounds, so the 400 pound barrel was divided into two parts, to be screwed back together for action. It took at least 5 mules for the barrel, carriage and associated bits, then more mules for ammunition and powder.
The original prototypes were manufactured my Elswick Ordinance, the armaments branch of the Armstrong Whitworth Company, a major British manufacturer. It was a rifled muzzle loader and was probably the smallest gun they ever made. These were sent to Afghanistan for trials and were successful. A Mk. II version was then manufactured by the Royal Arms Factory in Woolwich, England, which had been a gun foundry since 1717.
Screw Gun in Firepower Museum. Photo by Mike Morrison
Specifications. The steel gun's bore was 2.5 inches and the official nomenclature is 2.5 inch RML (for rifled muzzle loader). It was also called the 7 pounder gun, as the shell it fired weighed around 7 pounds. The gun could propell a shell to 1400 ft. per sec. with a charge of 24 oz. of black powder. The 66 inch length of the bore gave it an effective range of 4000 yards.
The gun was used all over Afghanistan and India, and was even present in the Sudan at the Battle of Abu Klea, during the relief of Khartoum. It was also well used in Africa by the West African Frontier Force and the King's African Rifles. By 1903, muzzle loading was out, and a breechloading version was adopted, but was considered a 10 pounder, as the shell size was also increased. It had a strange breeching system, developed by the French, with a mushrooming bladder to seal the breech, but was considered workable, as hundreds of rounds could be fired without repair. By World War I, a newer breech and bigger shell was introduced, and was known as the 2.75 inch BL (breech loading) Mk I. It fired a 12.5 pound shell.
Indian Artillery unit with Screw Gun
In The Canadian Magazine from 1900, they state that "the Screw Gun has proved most successfull in dislodging unruly natives". The mountain guns were immortalized by Rudyard Kipling in his poem, Screw Guns.
"You can go where you please, you can skid up the trees,
But you don't get away from the guns!"
The newly developed Camel Corps in the Sudan in the 1880's carried Screw Guns, which were used in the battles of Abu Klea and Ginnis. They were operated by the Naval Brigade. It took six camels to service one gun and it's ammunition. The guns were used on the corners where the British liked to form a square to fight, since the Zulu Wars. One corner was covered by a Gardner Gun.
Screw Guns were mainly developed for Afghanistan and the Indian Northwest Frontier. The British were there to counter Russian aspirations, and further their Empire, but in the meantime had plenty on their plate from local warlords and such. An adventurous young man in the British Army could depend on plenty of combat on the frontier. During punitive expeditions, which happened a lot, Screw Guns were hauled to mountain tops along the route of march to cover the main columns. Since the Great Mutiny of 1857, the only artillery allotted to Indian gunners was the mountain guns. They were officered by the best Britain had, and competition for a place in the Indian mountain batteries ensured quality recruits. There was no shortage of action for these guns.
Video of later British mountain gun