I claim the ornamental design for a gun case, as shown and described.
FIG. 1 is a perspective view of a gun case;
FIG. 2 is a front elevational view of FIG. 1;
FIG. 3 is a rear elevational view of FIG. 1;
FIG. 4 is a right-side elevational view of FIG. 1;
FIG. 5 is a left-side elevational view of FIG. 1;
FIG. 6 is a top plan view of FIG. 1; and,
FIG. 7 is a bottom plan view of FIG. 1.
The broken lines showing a logo in FIG. 3 depict environmental subject matter and form no part of the claimed design. The remaining broken lines represent stitching and are part of the claimed design.