I don't know, but would have thought that if you shoot even an air rifle and the pellet goes out side your property you are breaking the law. That said if you shot straight up in the air and hit it would the pellet be classed as leaving your property?
TC
With an air rifle its illegal if your pellet leaves your boundary but with a shotgun its civil tresspass if your shot leaves your boundary so not a police matter so get the shotgun out ..