To humanely kill a 180-pound animal, a much more powerful firearm would be required. A centerfire rifle with a caliber of at least .308 Winchester or 7mm Remington Magnum would be more appropriate for this task. These cartridges have a significantly higher muzzle velocity and energy than air rifle pellets, and they are capable of delivering a lethal blow to a large animal.
It is important to note that hunting regulations vary depending on the jurisdiction, and some areas may have specific restrictions on the use of air rifles for hunting. Before attempting to hunt any animal, it is crucial to research the local regulations and ensure that you are using the appropriate firearm and ammunition.