1. A FIREARM HAVING A SEMI-AUTOMATIC REPEATING ACTION COMPRISING IN COMBINATION, A RECEIVER AFFORDING A HOUSING FOR SAID ACTION, A CHAMBERED BARREL FITTED TO SAID RECEIVER, SAID RECEIVER AND BARREL ASSEMBLY BEING MOUNTED IN A BUTT STOCK AND FORE-END ASSEMBLY, A MAGAZINE FOR RETAINING A QUANTITY OF LOADED AMMUNITION TO BE FED AUTOMATICALLY TO THE CHAMBER IN THE BARREL WHEN THE SAID ACTION IS ADJUSTED FOR SEMI-AUTOMATIC FIRING, A TRIGGER MECHANISM COOPERATING WITH A HAMMER MOUNTED WITHIN THE RECEIVER, A BREECH BOLT SLIDABLY MOUNTED WITH RESPECT TO SAID RECEIVER, SHIFT MEANS FOR SELECTIVELY CHANGING TO SINGLE SHOT OPERATION AND BACK TO SEMI-AUTOMATIC OPERATION AT THE OPTION OF THE SHOOTER, SAID SHIFT MEANS INCLUDING A LATCH BAR AND ACTUATOR MEMBER, SAID LATCH BAR INCLUDING A HOLE THEREIN PROVIDED WITH A LOCKING NOTCH DISPOSED FOR ENGAGING SAID ACTUATOR MEMBER AND MEANS FOR SELECTIVELY ENGAGING SAID BOLT, TAKE DOWN MEANS FOR RELEASABLY ENGAGING SAID RECEIVER AND BARREL ASSEMBLY WITH THE BUTTSTOCK AND FORE-END ASSEMBLY AND A SAFETY MECHANISM HAVING A LOCKING LEVER ASSOCIATED THEREWITH WHEREBY SAID ACTION MAY BE RENDERED INOPERABLE