No Military, but there is a F Grant No.741 N/5th RA on the roll, and N/5 served in the Zulu and 1st Boer Wars. Could well have been out with Chelmsford returning to Rorke's Drift during the evening of 22nd Jan 1879.
I did find a Frank Grant attested 22 April 1887 into 3rd Brig S D Batt Royal Artillery [a Militia Regt] at Sandown Isle of Wight, this also states he had already served 12 yrs in the Royal Artillery being discharged at Leamington. He was discharged for the second time on 31 May 1898, giving a total service of 23 years.
Born Newport Isle of Wight 1856, he married a widow Ellen Newbery in Freshwater I o W, 21 April 1888, the 1901 census give them living School Green Freshwater, he is a Labourer, by the 1911 census he is a widow living Totland Bay.
Could well be the same man from N/5 RA.