The ornamental design for a pneumaticblowgun, as shown and described.
FIG. 1 is a front and right side perspective view of a pneumatic blow gun showing the new design.
FIG. 2 is a front view thereof.
FIG. 3 is rear view thereof.
FIG. 4 is a right side view thereof.
FIG. 5 is a left side view thereof.
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
Elements drawn in broken lines in FIGS. 1-7 are included for the purpose of illustrating environmental structures but form no part of the claimed design.