the heavier (denser) it is, and, more angular, the faster cutting..........
Commercially, I use black beauty (copper slag) for that, or, garnet, although, the latter is pretty expensive.....although, either can be screened and re-used
regular, washed 20/30 grit is good for throw away.
I use a 1/8" nominal nozzle, 100 PSI, which requires about 100 cu. ft./min.
Good luck,
Henry