These are excerpts are from 2 different specifications used by the same company. Notice the difference in bold. Who would get to decide what is either "practicable" or "practical" I assume the words here should have been the same and it's a typo. No where in the specification does it detail what a "practicable" or "practical" size shot would be for a given intensity range.

Seems odd, what if the user only has ASH-170 and nothing else?

1)
"Shot size selection. Unless otherwise specified on the drawing , the nominal shot size shall be the smallest size practicable to produce the required intensity. The nominal shot size used on fillet surfaces shall not be greater than 1/2 the fillet radius. For slots or other apertures, through which shot must pass to peen shielded critical areas, the nominal shot size shall not be greater than 1/4 the diameter or width of such aperture."


2)
Shot Size Selection. Unless otherwise specified on the engineering drawing, the nominal shot size shall be the largest size practical to produce the required intensity. The nominal shot size used on fillet surfaces shall not be greater than 1/2 the fillet radius. For slots or other apertures, through which shot must pass peen shielded critical areas, the nominal shot size shall not be greater than 1 the diameter or width of such aperture.