Classification of shotguns is generally straightforward, but as the traditional 12 bore has now been around for well over 100 years, it could certainly be argued that some of them must be antiques, and might therefore benefit from section 58(2) of the Firearms Act 1968, which gives exemption from normal certification procedure to antique firearms.
Other more unusual calibres may qualify as antiques due to the obsolescence, or unavailability of their cartridges.
Where accidental discharge is an issue, careful examination should be made to ensure that no faults exist in the mechanism, or that the trigger pressure required to fire the weapon is not unusually light.
Because of the progressive spread of pellets fired from a shotgun, the range from which a shot is fired can often be determined quite accurately by conducting comparative tests, although it would not normally be possible to identify a particular shotgun from which shot was fired.
A broad indication of the type of cartridge used in a shooting can be made by examination of recovered shot, which is not only produced in many sizes, but is now made from different metals including steel, tungsten and bismuth in addition to traditional lead.