I believe it says Butts Fatigue(s). The letter "l" in other words is looped and the "t" mostly do not have their cross piece. Butts fatigue, working in the butts at a rifle range.
There are a number of references in contemporary newspapers in the 1850-1900 period in accounts of army doings referring to the "butts fatigue party" and "butts fatigue men".
MaxD