NMAC BETWEEN ACR-MLG IN DESCENT AND GA-SMA CROSSING IN CRUISE.

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ACFT WAS CLRED FOR THE SCY 9 ARR. FLT WAS GIVEN VFR TFC AT 6500'. APPROX 15 MI S OF SCY VOR; NO JOY. XING SCY IN THE DSCNT TO MAKE A RESTRICTION 6 MI NW ON THE 313 DEG R AT 7000'; AFTER ROLLING WINGS LEVEL DSNDING THROUGH 9000'; WE OBSERVED AN SMA XING RIGHT TO LEFT AT OUR ALT. WE ESTIMATE HE CROSSED OUR NOSE BY 500' WITH LESS CLRNC AS WE WENT BEHIND HIM ON OUR LEFT SIDE. NO EVASIVE ACTION WAS TAKEN AS THERE WAS NO TIME TO DO SO. ATC RESPONDED WITH NO TARGETS IN OUR AREA. REMAINDER OF FLT WAS NORMAL WITH THE EXCEPTION OF THE CREW HAVING TO CHANGE SHORTS! EVENT OCCURRED DURING A VERY BUSY TIME IN THE COCKPIT. OUR QUESTION TO OURSELVES WAS: DID WE MISUNDERSTAND THE '6500'' TFC AND HIS RANGE AS WELL? DID WE PRECIPITATE THE NEAR MISS BY A POSSIBLE MISUNDERSTANDING? WE DON'T KNOW! WE HAVE REQUESTED ATC VOICE AND RADAR TAPES THROUGH AN ATTORNEY FOR OUR INFO. BOTH PLTS WERE OUTSIDE DURING THE DSCNT. HOWEVER; THE ACFT WAS IN A 20 DEG LEFT TURN AS THE OTHER ACFT APCHED FROM OUR RIGHT. OBVIOUSLY WE COULDN'T SEE HIM UNTIL WINGS LEVEL AND THEN UNABLE TO TAKE EVASIVE ACTION. THIS INCIDENT OCCURRED OVER AN EXTREMELY BUSY VOR CORNER POST WITH AN ACFT W/O A TRANSPONDER (OR TURNED OFF TRANSPONDER) NOT TALKING TO ATC. I RESPECT AN AIRMAN WAITING TO FLY VFR. HOWEVER; WHEN THROUGH HIS POOR JUDGEMENT HE ENDANGERED MY CREW AND PAX; THIS IS UNSATISFACTORY. DO WE HAVE TO MAKE THE WHOLE USA CTLED AIRSPACE? CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR HAS NOT HEARD BACK ON REQUEST FOR TAPE READOUT. SMA WAS AT CRUISE AND COULD HAVE BEEN AT 8500'; THE PROPER ALT FOR HIS DIRECTION OF FLT. WAS SO CLOSE COULD SEE PLT OF SMA LOOKING OVER HIS SHOULDER APPARENTLY TALKING TO PAX BEHIND HIM IS ACFT. ARTCC CTLR DID STATE THEY HAD A FAINT TARGET AT MLG 6 O'CLOCK POSITION AFTER TOLD OF NMAC SO FEELS IT WAS SECOND ACFT AND NOT SAME ONE POINTED OUT EARLIER. ADVISED COMPANY BUT GOT INDICATION THEY WOULD NOT FILE FAA NEAR MISS REPORT AND NEITHER WAS ARTCC.