The ornamental design for a gunstock, as shown and described.
FIG. 1 is a perspective view of the gun stock of the present invention;
FIG. 2 is a right side view of the gun stock of FIG. 1;
FIG. 3 is a left side view of the gun stock of FIG. 1;
FIG. 4 is a top view of the gun stock of FIG. 1;
FIG. 5 is a bottom view of the gun stock of FIG. 1;
FIG. 6 is a front view of the gun stock of FIG. 1; and,
FIG. 7 is a back view of the gun stock of FIG. 1.
The broken line showing of FIGS. 1,4,5 and 7 is included for the purpose of illustrating portions of the gun stock that form no part of the claimed design.