At the RKO Cinema Theatre , Leicester Square , London , a collection of American gangster ' s weapons is on display . Here , a sawn - off shot gun , one of the first weapons used by the racketeers before the introduction of automatic rifles . This is an ordinary shotgun sawn off at both barrels and it is possible for this to be carried up the sleeves with the butt under the arm pit . The reason for this being sawn off is that the very powerful charge has a far greater spreading range and can cause more damage . It is possible to kill from three to four people with just the charge from one barrel . 21 October 1931