The ornamental design for a portableshootingplatform, as shown and described.
FIG. 1 is a perspective view of the portable shooting platform embodying the new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
FIGS. 1-7 show portions of the portable shooting platform in broken lines. The broken line portions are shown for environmental purposes and form no part of the claimed design. The broken line segments immediately adjacent the solid line portions of the design define the boundary of the design, but do not themselves form part of the claimed design. The oblique line shaded portions of the portable shooting platform define the claimed region.