Locks for firearms

A removable lock for a firearm having a revolving cylinder with bullet-receiving chambers, said lock comprising:

• a body portion sized for insertion into one of the chambers when the cylinder is in an open position;
• means for preventing removal of the body portion from the chamber so as to prevent closure of the cylinder and comprising an expandable element located at or adjacent to an end of the cylinder when the body portion is within the chamber;
• and
• a key-actuated rotary element for expanding the expandable element;
• wherein
• the body portion comprises an outer tubular body having at one end a head of a transverse dimension greater than the diameter of the chamber, the expandable element is at the opposite end of the body and in an unexpanded condition has a transverse size less than the diameter of the chamber to enable said opposite end of the body to pass through the chamber, the expandable element when in an expanded condition being of such a transverse size that withdrawal of said opposite end of the body through the chamber is prevented;
• the key-actuated element comprises an inner body mounted within the outer body for rotation about the axis of the outer body, the inner body having a cam movable on rotation of the inner body to effect expansion of the expandable element;
• and
• the outer body includes longitudinal slots extending from said opposite end and the expandable element is defined by formations provided on said opposite end such that rotation of the cam effects radially outward movement of the formation by opening of the longitudinal slots.