The ornamental design for an adjustablefirearmstock, as shown and described.
FIG. 1 is a perspective view of an adjustable firearm stock of the present invention;
FIG. 2 is a front view of the adjustable firearm stock of FIG. 1;
FIG. 3 is a left view of the adjustable firearm stock of FIG. 1;
FIG. 4 is a rear side view of the adjustable firearm stock of FIG. 1;
FIG. 5 is a right side view of the adjustable firearm stock of FIG. 1;
FIG. 6 is a bottom view of the adjustable firearm stock of FIG. 1; and,
FIG. 7 is a top view of the adjustable firearm stock of FIG. 1.
The ornamental design that is claimed is shown in solid lines in the drawings. The broken (dashed) lines shown in the drawings are included for the purpose of illustrating environmental elements only and form no part of the claimed design.