Take a shotgun
(or buy one), preferably a double-barrelled
model. Cut off part of the stock, and any non-structural barrel
, and presto, you have a sawn-off shotgun. This weapon has a particularly resonant cultural place in Britain
as, until recently, it was the weapon of choice amongst British criminals.
Whilst other firearms are subject to draconian legislation (if you want to own a submachine-gun, the Home Secretary has to give you permission, and you have to have a very good reason), shotguns and shotgun ammunition are relatively easy to come by, especially out in the countryside (where people worship spirits older than Satan). Bear in mind that, as part of your pact with the Home Office, the Police can inspect your security arrangements at any time, and they will not be too happy to find you tooling up for a blag like a tea leaf.
Full-sized shotguns are heavy, hard to conceal, and extremely unwieldy (despite which, Jack Carter carried a full-sized shotgun in 'Get Carter' - in reality he would probably have sawn the end off). A sawn-off shotgun, on the other hand, is small, can be hidden underneath a bomber jacket, and has great psychological impact on those on the nasty end. When accompanied with a cry of "Excuse me, Sir, I am carrying a sawn-off shotgun. Please give me your money", a criminal thus equipped is a formidable disorder-making machine.
Under UK law, sawn-off shotguns have no legal application (the dispersion pattern of the shot is such that a sawn-off shotgun is ineffective beyond a few feet), and if you are found in possession of one, you will have your shotgun certificate revoked, probably forever, and you might well end up going to prison, especially if you are waving the gun around in public.