M276 dim tracer, 7.62x51mm, post 1994, purple tip, type 6, headstamp LC/97
Would this use the Infrared Tracer Compostion R440 - Barium perioxide, strotium peroxide, calcuim resonate, magnesium carbonate?
Do a search. There were a couple of threads on the Dim Tracers, one not long ago. I don’t recall if they detailed the composition.