The possession of firearms and ammunition in Great Britain is regulated mainly by the Firearms Acts 1968 (as amended). You'll find guidance, good practice on firearms law, and forms for applying for approvals under the law.
Firearms law: guidance to the police is a comprehensive piece of guidance intended to assist consistency of practice between police forces and to encourage an informed understanding among firearms users of the considerations involved. This is the most recent version - 2002.
The 2011 leaflet 'Air weapons: a brief guide to safety' contains information on the safe handling and storage of air weapons, the different types of air weapons and air weapons and the law.
Other publications include:
Air gun owners: new legislation - leaflet from 2004 provides advice on how to comply with the ban on self-contained gas cartridge weapons
Deactivation of firearms - these specifications were revised in 2010
Firearms and ammunition handed in during the firearms amnesty 2003 - a table outlining the types and numbers of weapons and ammunition handed over
Police use of firearms
For general information for the police on the use of firearms, you need to go to the following pages on The National Archives: