hi grim
found this
Definition of a loaded firearm regarding airguns
22.13 Section 57(6) of the 1968 Act includes a definition of “loaded†in relation to shot guns and air weapons. An air weapon is to be treated as loaded if there is a pellet in the breech, even if the compression necessary to fire the gun is not present; and in the case of a shot gun or air weapon having a loaded magazine, the gun is to be treated as loaded, even though there is no round in the breech.
Source: Home Office - Firearms Law Guidance to the Police 2002
hope this helps
davy