You are right; the majority of British troops had the Lee Metford and or the Lee Enfield. With the earlier ammunition this may still have caused obscuring of targets through smoke . For a general impression of weaponry I site http://obscurebattles.blogspot.com/...urman-1898.html
where it states Quote''
Firepower was clearly in the allied camp. The Anglo-Egyptian army was equipped with the latest in artillery, small arms, and ammunition. Some historians have armed the British infantry in the Sudan with the Lee-Metford magazine-fed, bolt-action rifle. While this was still a black-powder weapon (meaning it would have enshrouded a firing line in choking smoke), it had a max range of 1,800 yards, a ten round magazine, adjustable sites and was capable of laying down an incredible amount of fire on a distant mass target like 17,000 Dervishes. My own research has indicated that most of the crack infantry (in which I'd count the regiments present at Omdurman, like the Grenadier Guards) were already being given the smokeless-powder version of this rifle, the Lee-Enfield, which was to become the standard British infantry weapon until the 1950s.
Martini Henry. The Egyptian and Sudanese
troops were armed with the older Martini-Henry (the infamous rifle of Isandhalwana legend), a single shot breechloader using black powder ammunition (which would have obscured the target from a firing line after just a few rounds). However, by 1898 the Martini was a rugged, reliable weapon with a max range comparable to the Lee-Metford and a rate of fire of 12 rpm. While the Dervishes were able to get closer to the Egyptians and Sudanese regiments than they were to the British, they were still stopped dead at several hundred yards. One lone, old man carrying a flag was said to have staggered to within potato-chucking distance of MacDonald's brigade, only to have been shot down clutching his flag, bless his heart.
Maxim Machine Guns.
Then we have to consider the dozens of Maxim machine guns on the allied side. The Maxim was a breakthrough in machine gun design, which had, from the Gatling to the mitrailleuse, been prone to jamming at the worst possible time. But the Maxim, water-cooled and belt-fed with a single barrel, was far more reliable. It put out a rate of fire of 550 rpm, so that a couple of men manning one could be worth a whole company. These guns, and other water-cooled versions based on its original design, would also be widely used during the First World War by all sides, and were still in wide use during the Second World War.
The allies also enjoyed an overwhelming advantage in artillery. The 52 guns in the army and on the gunboats were quick-firing, extremely accurate out to over 3,000 yards, and lobbed a high-explosive lyddite shell that had more destructive force than anything seen in prior wars. These guns were also a staple of the wars of the early and mid-twentieth century. So what we have in the allied force that faced the Ansar at Omdurman was essentially a fully modern army, armed with everything the armies had in WWI except airplanes and tanks.''Unquote.
A good history and development detail can be seen at https://en.wikipedia.org/wiki/Maxim_gun
whilst below shows the weapon and its inventor; American-British inventor Hiram Stevens Maxim in 1883.