I claim the ornamental design for an oval shaped firearm bag, as shown and described.
FIG. 1 is an isometric view of an oval shaped firearm bag showing my new design.
FIG. 2 is a front elevation view thereof, with the opposite side being a mirror of that shown.
FIG. 3 is a left side elevation view thereof.
FIG. 4 is a right side elevation view thereof.
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken lines in the drawing that show environment of the oval shaped firearm bag form no part of the claimed design. The broken lines showing stitching do not form part of the claimed design.