I can't be all that specific, but here goes:
-It could be taken around 1902 or later, perhaps during the uprising of 1914.
- I think those are the officers in the centre.
- I think these are probably not full-time soldiers. My guess would be volunteers, town guard, or militia. I say this because there is a rather casual uniform [see the belts, boots, hats, ties etc - all vary], and the age of the soldiers is varied.
- The appearance suggests [if Boer war] pro-British forces. Or [if after 1910], pro-Union forces - the slouch hats are up on the left, and the rifles are, I think, Lee Enfield Mk I*s [there is a safety catch, 10-rd magazine, and no clearing rod].
- The bandoliers are a mixture of British mounted infantry type and Boer style. The bandoliers may not be Boer captures, the Union defence force purchased similar ones.
Would any of this make sense from what you know of your ancestor?
The past is not dead. In fact, it's not even past.