We claim the ornamental design for a firearm handguard, as shown and described.
FIG. 1 is a bottom, right side isometric view of a firearm handguard, which shows the lower right side and distal end of the handguard.
FIG. 2 is a bottom, plan view of the handguard shown in FIG. 1.
FIG. 3 is a top, plan view of the handguard shown in FIG. 1.
FIG. 4 is an end elevation view of the handguard shown in FIG. 1 showing the proximal end of the handguard.
FIG. 5 is an end elevation view of the handguard shown in FIG. 1 showing the distal end of the handguard; and,
FIG. 6 is a side elevation view of the handguard shown in FIG. 1 showing the right side of the handguard; the undisclosed opposite side being a mirror image thereof.
The broken lines shown herein are for illustrative purposes only. The broken lines and the areas within the broken lines form no part of the claimed design.