LINK to full instructions.
Made from three real world weapons, the M41-A even has a cool sounding name. The M1A1 Thompson makes up the bulk of the weapon, and the Remington 870 shotgun is the guts for the "grenade launcher". Carefully hidden inside a SPAS-12 heat shield cage and pump handle. The filming hero prop was made with a metal shroud, and is truly a work of art.