The Boers were armed with a wide variety of firearms.
Many Boers armed themselves with their own rifles and, often, shotguns, while the governments of the Boer Republics contracted with European nations to supply small arms and heavy weapons.
It's not true that all organized Boers units were armed with Mauser rifles.
They also had cast offs like the Portugese Guedes single shot rifle as well as Krag Jorgenson rifles.
Also, there were numerous model Mauser rifles in use, not just 1888 Commission rifles. The Boers also had Model 1893s and 1897s.
Given that the Second Boer War happened from 1899 to 1902, it's also possible that they had K98s at some point, as well.
And, here's a very interesting tidbit...
Boers also had Martin-Henry single shot rifles that had been manufactured in Belgium by Westley Richards for supply to the Boer Republics at a time when Britain and the Boer Republics were still amicable.
The one big problem that the British ran into was artillery. British artillery was still black powder at the time, making sighting their guns very easy.
The Boers, on the other hand, were armed with Krupp rapid firing (1 lb Pom Pom) guns which used smokeless powder, making them very difficult to spot and neutralize.
One favored Boer tactic was to fire slow ranging shots, walking them onto target.
Once they were on target, they would use the Pom Pom's automatic mode to drop an entire belt into the British guns to devastating effect.
The Boer Pom Pom was so effective that the British and commonwealth forces took them into service when they captured them.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.