The main reason that they allow a .22 is to put an animal down, if you injure it, without destroying the possibility of a mount. Any ethical hunter would not use a .22, a .38, a 9mm, ect for their inital shot, hugher power 'mag' calibers are the only things ethically that should be used in my opinion, and even those should only be used (again in my opinion) at a range of less than 75 yards, even with a scope.