A firearm enclosure for enclosing a firearm, such as a black powder pistol or rifle, and includes and elongated sleeve portion having an opening at one end into which the firearm is inserted. This opening forms a watertight seal and enclosure, preferably with a resealable closure arrangement. The other end of the sleeve is closed and receives the muzzle of a firearm. This end of the sleeve is enclosed by a material which, while being waterproof, offers little resistance to puncture by a bullet exiting a muzzle, thereby minimizing any deflection or loss of momentum of the bullet. Use of the enclosure protects the firearm during use from the elements such as rain, sleet, snow, fog, and external humidity.