Abstract: An adjustable gun holster is described. Embodiments of the holster include a first member for receiving a buttstock of a gun and a second member for receiving a forestock/barrel of the gun. The holster can further include a pair of attachment structures to removably couple to a shoulder strap of a pack. The holster can be adjusted to fit guns having differing lengths. For instance, the holster can be adapted for a short barreled shotgun and a long barreled rifle. To holster varying sized guns, a strap connecting the first member to the second member can be lengthened and shortened.