Air Rifle Hog Hut Using a GAMO Hunter Extreme Air Rifle. The ultimate in air rifle power. The Hunter Extreme .22 cal. air rifle by GAMO offers a devastating combination of power and velocity to provide you with the ultimate air rifle hunting experience. With a muzzle energy of 23.6 ft-lbs (32 Joules) the Hunter Extreme .22 cal. can handle any varmint situation.