The use of the Gatling Guns at Ulundi, by No. 10 Battery, 7th Brigade, Royal Artillery, under the command Major J. F. Owen, was indeed the first combat use of the Gatling by men of the British Army. Obviously the Royal Navy had used them at Nyezane, as Clive points out and at Gingindlovu.
Garnet Wolseley did have a Gatling Gun Battery in the 1st Asante War, but they were never deployed in combat.
From: 'The History of the RA from the Indian Mutiny to the Great War'; Headlam.
1. The Second Afghan War, 1879. 'There was a new unit "The Gatlings", consisting of two Gatling guns organized on mountain battery lines.' 'Arrived in the Kurram direct from England'. The were lots of problems, incomplete stores, had to make bits and pieces, used stuff from a captured Afghan bty. 'But the arrangement of the ammunition drums was always liable to cause jams unless the drill was absolutely accurate, and at Charasia, the first occasion on which the guns came into action, they failed from this cause, and were little used afterwards. The last heard of them is in the defence of Sherpur Cantonment.'
2. South Africa, Ulundi, 1879. The gatling battery, 10 Garrison Bty, 7 Garrison Bde (Maj JF Owen) was part of the 'flying column' that was not part of 1st or 2nd Divisions.
3. The Egyptian Expedition , 1882. In this campaign Gatlings were operate by sailors in the action at Magfar. RHA had to send horse back to drag the gatlings through the last couple of miles of sand.
4. NW Frontier, Black Mountain Expedition, 1888. 2 Sects of Gatlings - Capt Findlay & Lt Eyre. 'And then occurred a repetition of the charge of the Fanatics in the Ambela Expedition of 1863. A body of Ghazis who had been concealed in a nullah made a desperate attempt to break through the line - only to be shot down by the infantry and Gatlings.' ''The Gatlings used in the Black Mountain did not jam, but their range was found insufficient, and the employment of artillery personnel with machine guns found many objectors.'
No record of Gatlings used in the Ashanti Expedition 1873, although they did have rockets (considered useful weapons against primitive opponents). However, the 1895 expedition did have a battery with mixed armament, (6 x 7-prs, 2 rocket 'troughs' and 2 Maxims). These were manned by the Gold Coast Constabulary and 12 RA NCOs under Capt Benson. The bty was never engaged.